Because I have a relatively short commute, and rarely anticipate needing my full 100% pack capacity, I have chosen to charge my truck to an 80% SOC on a daily basis to maximize battery life. One nice thing about the 80% level is that most batteries can be charged at a relatively high rate of speed up to 80%, and then you need to slow down the charging a bit to prevent them from overheating. (This is why DC Quick Chargers will quickly bring an empty battery up to 80%, but then slow down quite a bit after that.)

My first attempt at programming an 80% charging profile was very simple, just set  MaxV to 128.5 and set the TermC (termination current) to 2 amps. This works well, it gets the pack voltage up to 128.5 volts and holds it there until the battery stops accepting much current. The only issue is that it is wasting time, because for a good amount of the charging period the current flowing into the battery is less than the maximum 30 amps (4.0 kW) that the chargers can produce. The charging curve looks like this, with a 3hr 20 min total time:

In an effort to speed up my charging, I set the MaxV to a higher amount ( 128.9 volts) so that at the 128 volt level the battery pack would still be accepting a higher current, and then set my TermC to the highest level my EVCC allows (10 amps). This results in a charging curve that looks like the following with a 2 hr 21 min time:

As you can see, I spend more time delivering 30 amps before the current draw from the pack starts to drop off, and the curve reaches the cutoff point much quicker. My EVCC currently limits the TermC parameter to 10 amps or less, probably because they have not anticipated somebody trying to charge only to 80% as quickly as possible. In both cases the battery pack resting voltage after the charging terminated was 128.1 volts.

If I could set the TermC parameter on my EVCC to 20 or 25 amps it would allow me to set the MaxV up higher (131?). The goal would be to find a voltage setting such that the pack would be drawing 20 or 25 amps right when it hit the 128.5 volt level. So my curve would basically be flat, full on charging at 30 amps up until the very end when it would start to taper off and the charging would end at 25 or 20 amps.
I’m not worried about setting the MaxV higher than the actual voltage I’m attempting to hit, as it is still much lower than my pack’s actual max voltage, and if something were to change with the pack chemistry making it miss the TermC cutoff, the MaxV would still stop the pack from reaching 100% charged. (and the termination timeout would eventually hit.)

This is the end of my main thought, but you can continue reading for…..

Extra Info about my pack, charging to the 80% level, etc…

The 48 modules from my Nissan Leaf battery pack (LMO/LNO chemistry)  are arranged in a series of sixteen sets of 3 parallel cells. This gives me a 180Ah battery with an absolute maximum voltage of 134.4 (4.2 volts per cell). In actual use the 4.2 VPC level should never be reached, if you charge the cells to 4.1 volts per cell they are around 99% charged. As the extra 0.1 volt difference between 4.1 and 4.2 doesn’t really buy you much extra capacity,  most people use 4.1 volts per cell (131.2 volts) as a safe “full” or 100% capacity on the Leaf Cells.  My Mini-BMS units will start to shunt voltage at 4.1 VPC, and raise an over-voltage alarm at 4.2 VPC.

However, if you charge the cells to 4.0-4.01 VPC (128-128.5 volts) that corresponds to about 80% of their maximum possible capacity. To maximize cell and battery pack life, you want to minimize the time the cells are fully charged or fully discharged. If you can keep the cells between a 10%-80% state of charge (SOC) it will maximize their battery life.

Keeping them above 10% SOC is easy…don’t drive until they are empty. Keeping them at or below 80% SOC is also easy, simply turn off your charger when they are only 80% charged.   This is why the early Nissan Leafs had the option to only charge the battery to 80%. (Removed in the newer Leafs due to EPA regulations on how maximum range is calculated.)

If you want the extra 20% of range that charging to 100% SOC would give you, it is better to charge to 100% and then immediately discharge the pack by driving it (as opposed to leaving it sitting at 100% charge all night).  This is one reason why Nissan Leaf’s have a charge timer, so that you can tell the charger to finish just before you start your daily drive. (The other reason is so that you can tell it to start charging only after the low cost nighttime electricity rates start, if you are on a time of use metering rate plan.)

My 2nd charging profile will be a 4.1 VPC full 100% capacity charge, for when I feel the need to really go long distances. (or to get the pack ready for a top balancing equalization charge, my future 3rd charging profile.)

Driving down the road today I smelled a plastic/electrical burning smell, which caused me to stop the truck and run around it quickly checking for any problems in my new Leaf modules. After verifying that they were not on fire, smoking, bulging, or even warm, I sniffed around the truck and decided the smell was emanating from under the hood, and eventually traced it to near my DC-2-DC converter (which keeps my 12 volt accessory battery charged up from the main 128 volt pack, replacing an alternator on an ICE vehicle). When I checked on the accessory battery voltage, it was 13.8 volts instead of the 14.5 volts that normally shows up when the DC-2-DC converter is working, so I thought that I had blown that out.

As it turns out, the only thing that had melted was the leg of the 30 amp 12 volt fuse I have between my DC-2-DC converter and my 12 volt accessory battery. Note: the fuse did NOT blow. One leg of the fuse melted into the holder, melting one side of the fuse and the plastic holder. The DC-2-DC converter was still working (but no longer connected to the 12 volt accessory system), and all of the 12 volt components were working fine on the redundant battery power.

At the time this happened I had the headlights and fan blower on, so the 12 volt load was about as high as it gets, but I’d been driving around like that for several years without the fuse or holder giving me any problems.  The only explanation I can come up with is that the process of moving wires around for the Leaf Module install loosened up the fuse in the holder and caused a loose connection, and the added resistance heated the connection up until it failed. (Although the fuse looked to be fully inserted into the holder even after it melted…)

I will have to replace the fuse and holder, and I’ll probably zip tie the new fuse into the holder when I replace it.

My truck’s charge controller supports the J1772 protocol, and I have added a J1772 inlet I took out of the same salvage Nissan leaf that provided my LiIon battery pack.

I added the J1772 port, the “start charging” button, and a rotary switch to select between different charging profiles, as well as a 120 volt, 15 Amp RV inlet behind a flip up license plate.

When you have one charging inlet, things are simple and safe. When you have more than one, things can get complicated. In my case, I wanted to use the same charger(s) with both inlets. But I shouldn’t just wire them both up in parallel, because that would mean that the (male pins on the) RV inlet would be energized at 240 volts when charging via the J1772 plug, and it wouldn’t be good for somebody to reach in and touch them. Also, if somebody were to try and plug in the J1772 AND a 120 volt extension cable at the same time, they would be connecting a HOT (from the J1772) line directly to the Neutral line on the 120 volts (causing a short circuit). [Having the J1772 inlet energized with 120 volts is also undesirable, although slightly less dangerous, as the J1772 inlet is designed to be “finger safe”.]

To solve these problems, I used a large power relay rated at 30 amps to switch between my two possible power sources (J1772 & 120 volt RV inlet).The chargers are connected to the common power connector, the J1772 inlet is connected to the normally closed contacts, and the 120 volt RV outlet is connected to the normally open contacts (and the coil switching relay).

By default, the J1772 inlet is connected to the chargers. (For this application it is important to find a relay where BOTH the normally closed and the normally open contacts are rated at the full amperage, many “30 amp” relays are only good for 1-5 amps on the normally closed contacts and the 30 amp rating is only on the normally open contacts. Note that my chargers max out at an 18 amp draw at 240 volts, so 30 amps gives me a good safety margin. If I had a charger that could pull a full 30 amps I would have gone with a 40 or 50 amp relay.)

If anyone plugs a live extension cord into the RV inlet, it switches the relay (disconnecting the J1772 and connecting the 120 volt RV inlet). Even if the relay fails open or closed, only one of the two inlets is connected to the charger, and the other inlet is disconnected from everything.

The second 120 volt relay is used for “signaling” wires to control my EVCC. One side will disconnect my ProfileSelect wire from the rotary switch on the front air dam, automatically selecting the 120 volt 12 amp charging profile (due to infinite resistance to ground). The other side grounds the “Proximity” wire from the EVCC, telling it that a (non-J1772 compliant) power supply is attached. In this setup, the EVCC will direct the two chargers to only draw 12 amps of power, which is the maximum safe continuous current draw from a standard 15 amp 120 volt outlet. [It also supports “drive-away protection” which can prevent the truck from moving away until all of the charging cables are unplugged.]

This photo shows the 120 volt power wires, with pigtails that will lead off to the switching coils on the power and signaling relay.

Basically, I’ve tried to make the 120 volt plug as “idiot proof” as possible. If you plug an extension cord into it and press the “start charging” button, the truck will charge at the appropriate rate regardless of how the rotary switch on the front air dam is set.

Summary: I drove my truck 46 miles on one charge (and had some juice left over).

When you have an electric vehicle, everybody wants to know how far it can go.
I typically tell them “19,800 miles so far.”

But then you have to answer their real question, which is “What’s your range on a single charge?”. If you have a commercial EV like the Leaf or a Tesla, you can just refer to the EPA range figure for a nice apples to apples comparison. But when you have a conversion EV, the number is unique to your particular vehicle, motor, controller, battery pack and testing methodology. (And changes as the pack ages…)

I used to know the answer to that question for my truck with a (new) lead acid battery pack (“25-30 miles without killing the pack”), but I haven’t fully characterized the trucks’ power usage and range with the new (lighter weight, more powerful) pack made up of Nissan Leaf cell modules. My truck is heavier and has more air resistance than a stock Nissan leaf,  the motor/controller is slightly less efficient, and the (big fat!) tires have quite a bit more rolling resistance. I figured “half the range of a Leaf” would be a good ballpark estimate.

Also important to note is that temperature and the types of driving you do plays a big factor in the number of watt hours consumed per mile driven and hence, range. In my drive yesterday, I was able to maintain a speed of between 30-40 mph with very few stoplights, the temperature was around 70 degrees, and using only the headlights I averaged 326 watt hours per mile. When driving in the winter when the temperature is closer to freezing, using the heater full blast, doing small stop & go driving in the 25-30 mph range, I have seen energy usage above 700 watt hours per mile.

Because I do not (yet) have an amp hour meter installed in my truck, the only way I have to tell how much power I used is to re-charge it, and see how much power it takes to fill it back up. This is known as a “from the wall” measurement, as it includes any charging inefficiencies as well as the power used to drive the truck. The shorter my trip, the more charging inefficiencies influence the final numbers, so when I recharge after a short 4 mile trip in the winter, I can get a usage of 875 watt hours per mile.

The lack of an AH meter also means I have no “fuel gauge” other than the overall pack voltage and a cell low voltage warning “beeper” from my BMS system. (And ideally, the beeper will never go off!) With Lithium ion batteries,  overall pack voltage (and the individual cell voltage it is based upon) is not directly correlated to the state of charge except when the cells are nearing fully charged, or fully discharged.  However, I can get a general feel for the overall charge level by looking at the voltages of the cells when they are “resting” (not driving the truck, or just coasting along with my foot off of the accelerator).

Above 131 volts means that it’s  just been charged and is basically full (4.1 volts per cell).
When it gets down to 128 volts that means I’ve used about 20% of the energy. I have picked  120 volts (3.75 volts per cell) as my conservative “empty” point. [Some people would use 118 volts (3.68 volts per cell) or even lower.]

When I drove the truck to 46 miles, I was keeping an eye on the overall pack voltage anytime I was stopped (at a stoplight, for example) and I had resolved to abort the test (a small loop around my house) when it reached that point. However, it was late at night and I got tired of driving, so I quit before reaching my 120 volt cutoff point. When I finished the drive, my resting pack voltage was 122.8 volts (3.82 volts per cell average). I measured all the cells with a voltmeter to check and see how well balanced the pack was, and the lowest cell was 3.814 volts, while the highest was 3.85 volts. [So they are relatively well balanced, but could be better.]

When I re-charged, it took 15 kWh (15,000 watt hours / 46 miles = 326 wh/mi). Note that since I’m measuring this with an analog, uncalibrated kWh meter, the level of precision is necessarily low.

The theoretical capacity of a (new) Nissan leaf pack is in the 22-24 kWh range, depending upon how much of the pack you are willing to use. I’m trying to never use more than 18-19 kWh (80% discharged) to maximize battery life. Since 15 < 18, I didn’t quite drive to “empty”.

Assuming I had driven for 3,000 more watt hours at 326 wh/mi, I could have gone another 9.2 miles, or had a usable range of 55 miles. So, in good weather, not using the heater, driving moderately long distances at lowish (30-40mph) speeds with few stops, my range is in the 46-55 mile range, or about half that of a Nissan Leaf.

Now that it is summer, and outside temperatures are reaching 26-35 C (80-95 F), my dual TSM2500 (Rebranded CH4100) chargers are overheating. After about an hour charging at full power, they reach around 74 C (165 F) and shut down. The ThunderStruck Motors EVCC records this as a “normal” end charging event (because the Amperage output goes to zero), and for some reason it triggers a ground fault on my EVSE (perhaps they have a thermal switch that shorts the charger to ground to shut it down, or maybe my JuiceBox Pro 40 is just overly sensitive?)

I guess the overheating is to be expected, as the chargers are in a five sided box (with only the top open) and mounted to a piece of (thermally insulating) plywood. Although there is a tangle of wires in front of them, the wires really don’t interfere with the airflow as much as it looks like from this top view.

In my defense, the charger’s manual (v. 1.05) specified that I should leave a 50mm (2in) gap in front of the charger for proper ventilation and I left around 8 inches. It also noted that the “Working temperature” for the chargers was -25 to 55 C (-13 to 131 F). It didn’t mention anything about thermally bonding the charger to a heatsync.

As a temporary solution, I have re-configured my 80% charging profile to only run at 1.2 kW (8 amps total, or 4 amps per charger on a 128-131 volt pack). This is about 25% of the 15 amp max power that the chargers are capable of in cold weather. At this relatively low power, each charger is outputting just over 500 watts, and even in 32 C (90 F)  weather the charger temperature hold steady at 50 C (122 F).

Charging at one kW may not sound terribly fast (it’s not), but this workaround is actually fine for 95% of my charging needs, as I rarely need to refill more than 8-10 kWh (20-30 miles) per day of use, and L1 charging overnight works fine for most of my needs.

However, I purchased the dual charger setup so that if I was necessity charging away from home I could charge at a 4 kW rate, so I want to make improvements to my cooling so that I can run the chargers at full power (without them overheating after an hour) if needed.

ThunderStruck Motors suggested that I mount the chargers to an aluminum heatsync, which is a good idea, but difficult and costly to implement.

I have decided my first order of business is to drill two 4″ air intake holes into the bottom of my charging enclosure and duct them to the top of the chargers right over the fan using dryer hose. This will allow the fans to draw cool(er) outside air directly over the vanes on the charger, and keep the heated exhaust air from mixing with the cool(er) incoming air. Since the top of the box is open, the heated output air should have no problems escaping, as convection will assist the fans in exhausting the hot air upwards.  If adding intake air vents doesn’t solve my problem, then I’ll worry about making an alunimum heatsync plate to take the place of the plywood.

In an effort to counteract overheating, I have added cool air intakes connected via 4″ diameter ducts to the fans on my TSM2500 (CH4100) chargers.

I used a 4″ flush to the floor “snap-in” PVC floor drain (designed to be cemented inside of a 4″ PVC pipe) spray painted flat black as my intake, connected to a 4″ aluminum flex dryer hose (mostly ran straight through, but the flex hose allowed me to vary the length) with worm screw clamps (a.k.a. hose clamps). The single most expensive part of the install was the 4″ hole saw ($15 on ebay, or $20 at the store). I could have saved $5 by going with a less expensive vinyl dryer hose, but I like the rigidity and appearance of the aluminum.

I used some black electrical tape to dress up the ends, and black zip ties to hold the hose directly over the fan shroud on the chargers.

Outside of the truck, you really have to look to find the air vents (after I spray painted them black…)

The only “exotic” tool required was a right angle drill, which made it possible to create the holes without removing the enclosure from the truck. Going through two layers of sheet steel with the 4″ hole saw did exercise the drill. After the first hole it was warm enough (130 F) that I decided to give the drill a cool-down period before drilling the second hole.

The relatively small fans on the chargers will hold a piece of paper against the intake openings, so the ducts are working as intended and are definitely pulling outside air into the box to cool the chargers.  It was 100 F today and the chargers didn’t overheat in my short 1 hour test, but I will need to drive the truck on a long trip to really test them under load for multiple hours of charging at full power. Click here to read the update on effectiveness.

Here is a video of the install process:

I have successfully driven my S-10 Electric Pickup conversion powered by 48 modules from a salvaged Nissan Leaf battery pack. I have them wired in series, 16 sets of 3 parallel modules, providing 128 volts with 180Ah capacity (23 kWh).

It took me a full three days of work to make the swap and get the truck to a barely drivable condition. I have the cells hooked up with a warning buzzer on the BMS low voltage loop signal, but I do not yet have the charger fully connected. I anticipate another 8 hours of work to get the charger and pakTrakr system fully set up.

From a performance standpoint, the LiIon modules are much “stiffer” than the twenty 6V golf cart batteries they replaced, meaning that they do not suffer from as much of a voltage sag under high current draw. The lowest I was able to get the voltage to sag on the LiIon modules was down to 118 volts while accelerating up a very long steep hill at a 350+ Amp draw.

My 0 to 35 mph time is a respectable, but not exactly sporty, 9 seconds, limited now by my motor and controller instead of the batteries. (Anybody have a Zilla 1K they want to sell?)

The ability to accelerate from 35 to 50 MPH up a long steep hill is much better subjective performance than I was able to get out of the truck when using golf cart batteries. It helps that the 500 lbs of Nissan leaf modules are replacing 1200 lbs of golf cart batteries, so the truck is 700 lbs lighter now. This also improves the stopping distance. The handling is slightly lighter, but nothing is going to make an S-10 into a sports car.

Because I got a good deal on a wrecked leaf, and reduced my costs by parting out the rest of the car, the actual LiIon modules only cost me $1200 (less than a set of new golf cart batteries)! However, the overall upgrade cost me $4100 once I included the cost of a new charger, EVSE, and BMS system to support the LiIon batteries, plus all of the miscellaneous materials and tools I needed to build the batteries and cables. Not to mention the hundreds of hours of work. If I sell some of the old Lead Acid batteries I may slightly reduce that cost.

If you want to watch the entire job, I have an hour long video that has most of the action (at 16x real time), but it’s only recommended for people who really want all the gritty details. I’ve made another post with photos documenting the highlights of the upgrade process.

To make it more enjoyable to watch, please consider the following drinking game:

Take a sip every time:

• I speak to the camera
• I have to use my Flex-Shaft mechanical pickup  tool to retrieve something I have (accidentally) dropped (mostly nuts and washers)
• I (deliberately and repeatedly) bring a rapidly spinning table saw blade within 1/2 inch of 2.8 kWh worth of LiIon batteries.

Take a full drink when:

• I drop a battery
• I cause a large electrical spark

oops!

update: I edited the above video down into a “shorter” 28 minute version, that leaves out all of the boring mistakes and repetitive work. (it leaves in the exciting mistakes…)

The main process of upgrading my S-10 Electric Conversion pickup truck to use the Salvage Nissan Leaf LiIon modules took me 3+ days, and I still have a few more days of small jobs to finish before I can call the job completely done.

Day 1:
On the first day I removed all twenty of the existing lead acid golf cart batteries. This involved lifting the main piece of wood under the hood that holds the contractors, motor controller, and 12VDC voltage converter, as well as lifting the bed and removing all of my PakTrakr battery monitoring units. After manhandling 1200 lbs of lead out of the truck (only dropping one battery on its side…) I cleaned up the existing battery bays, replacing some rotted wood and dirty foam.

Finally, I placed 3 of the new “batteries” that I had built using Nissan Leaf modules in the rear battery bay. My CAD model was slightly optimistic, so I had to use a table saw to cut  1/2″ of wood off the end of each battery, and a cut off blade in an angle grinder to remove all of the excess threaded rod from the sides so that everything would fit.

I made a mistake here and used some cables that were long enough to bend easily, but the extra length made them stick up over the maximum height of the battery units, in a position that perfectly matched up with a steel beam from the bed of my truck.

(I ended up swapping them out for shorter connections that fit below the battery units the next morning, but this also required that I remove a battery module I had put in place.)
Oh yes, I also caused a good set of sparks when a loose cable accidentally shorted to a wrench I was using to tighten up the terminal on the other side of the battery unit. 16.4 volts at hundreds of amps added excitement to the day.

Day 2:
It rained all morning. While waiting for the rain to stop, I selected some short 00 gauge cables to use to fix the mistake I made yesterday, and filed their terminal lugs nice and clean down to the copper. Rain, rain, rain. After it stopped raining, it took me about an hour to disconnect the too-long wires and replace them with the shorter ones. It wouldn’t have taken so long except that the 4th back bay battery was in the way, and I spent 30 minutes trying to work around it, before finally giving up and pulling it out of the battery bay, after which I could quickly finish the re-connection.

Then I spent a few hours cutting plywood and foam insulation to re-line the front battery bays. Shout out to the good people at the local art studio, who donated the wood & insulation foam (on the curb) that they were getting rid of before the studio show..

It turned out that I had to cut the excess threaded rod off of the other four batteries that would be mounted in front of the axle as well.

Day 3:
No rain, but the temperature was much colder, and windy. After installing battery 6 of 8, I found out that one of my PakTrackr sensing units was mostly working, but the voltage readings were off by at least a tenth of a volt. Of course, it was the one unit with the extra long wire leading up to the front of the truck. I have a few extra PakTrakr units that I have purchased as backups (the company has stopped manufacturing them) so I plan on replacing it later. Because it is in one of the side battery bays, it will only require that I remove two of the batteries and re-wire the cable up to the front of the truck.

I will have each PakTrakr watching two cells, or 8.4 volts, so they think they are monitoring 16 eight volt batteries. This won’t give me a per-cell level voltage reading, but it should give me an indication of problems and a good read on any set of two cells. I also have a mini-BMS system on each cell for balancing, but on the monitoring side of things that just gives me a “yes/no” signal for the whole pack to shut down the charger (over voltage) or stop driving (low voltage), and I have to lift the bed to examine them and find out which specific cell is having the issue.

On the other side of the truck the existing PakTrakr leads were just a bit too short to fit over both of my (back to back) batteries, so I had to solder in a jumper wire and heat shrink the connections.

Day 4:
I placed the charger and EVCC in the front battery bay (drilling 3 holes to pass wires down to the front air dam….240 volt charging, 120 volt charging, and low voltage control wires. This allowed me to wire up the BMS loop to the low voltage alarm controlled by the EVCC, so that I could drive the truck around. (Actually wiring up the charger so that it can CHARGE the batteries will be my next priority….)

The balance of weight on the axles has shifted slightly towards the rear, as I removed 4 lead acid golf cart batteries from the very front of the truck (under the hood), and am only replacing them with about 25 lbs of charger. However, removing 240 lbs of weight behind the back axles should help things in the other direction. However, the headlights have not tilted up enough to need adjustment, so it appears that the overall stance of the truck has not changed much. (The stock headlights are not terribly blinding even if miss-adjusted, I’m considering swapping them out with an after-market HID kit.)

If you want to watch an hour long video of the process, check out the bottom of this other post….

As part of the Li-Ion battery upgrade procedure, I needed a charger that could be programmed to work with the Li-Ion modules and my BMS loop system.  I decided on the EVCC (Electric Vehicle Charge Controller) from Thunderstruck Motors paired up with dual TSM2500 ( a.k.a CH4100) chargers. The total system cost just under $1200 shipped, so it was quite economical for a 4.2 kW system. The trade off for the low cost is that you have to wire both chargers up to the battery pack and the J1772 inlet in parallel, requiring you to make two sets of Y adapter cables. Theoretically the EVCC can control up to 4 of the inexpensive TSM2500 chargers, but I think wiring up two is about the most I would want to do, and if you want a high power charger it would probably be better to purchase one or two PFC-3000 or PFC-4000 chargers (which also interface to the EVCC).

I really like the EVCC, as it supports the J1772 protocol and can monitor my mini-BMS loop both for charging as well as for a low voltage warning when running. It also supports the ability to disable the EV when the J1772 plug is inserted (drive away protection).

The first one I received had a few software/firmware bugs that required me to send it back for a re-flash (one of the bugs made it so that the bootloader couldn’t re-flash it in the field!), but after I received the upgraded module it has been working well and I haven’t noticed any more bugs.

I have it set up with a single charge profile so far, but it actually supports 4 charge profiles that can be user selectable via a resistor network on a rotary switch. I have installed the hardware to select different charging profiles and will be programming them in the future.

The two chargers, EVCC and a few relays (for switching between the J1772 port and 120 volt RV inlet) are attached to a piece of wood that fits into the former front battery bay of my S-10 conversion. Althought I COULD fit two more chargers in there, space would get tight, the wiring would be (more) messy, and I’d be worried about the airflow and cooling. As it is, I’ve found that 4.2 kW charging is plenty fast for me. I can take a 16 mile trip, which is much longer than my daily commute, and be recharged in 141 minutes.

Because I have a relatively short commute, and rarely anticipate needing my full 100% pack capacity, I have chosen to charge my truck to an 80% SOC on a daily basis to maximize battery life. One nice thing about the 80% level is that most batteries can be charged at a relatively high rate of speed up to 80%, and then you need to slow down the charging a bit to prevent them from overheating. (This is why DC Quick Chargers will quickly bring an empty battery up to 80%, but then slow down quite a bit after that.)

My first attempt at programming an 80% charging profile was very simple, just set  MaxV to 128.5 and set the TermC (termination current) to 2 amps. This works well, it gets the pack voltage up to 128.5 volts and holds it there until the battery stops accepting much current. The only issue is that it is wasting time, because for a good amount of the charging period the current flowing into the battery is less than the maximum 30 amps (4.0 kW) that the chargers can produce. The charging curve looks like this, with a 3hr 20 min total time:

In an effort to speed up my charging, I set the MaxV to a higher amount ( 128.9 volts) so that at the 128 volt level the battery pack would still be accepting a higher current, and then set my TermC to the highest level my EVCC allows (10 amps). This results in a charging curve that looks like the following with a 2 hr 21 min time:

As you can see, I spend more time delivering 30 amps before the current draw from the pack starts to drop off, and the curve reaches the cutoff point much quicker. My EVCC currently limits the TermC parameter to 10 amps or less, probably because they have not anticipated somebody trying to charge only to 80% as quickly as possible. In both cases the battery pack resting voltage after the charging terminated was 128.1 volts.

If I could set the TermC parameter on my EVCC to 20 or 25 amps it would allow me to set the MaxV up higher (131?). The goal would be to find a voltage setting such that the pack would be drawing 20 or 25 amps right when it hit the 128.5 volt level. So my curve would basically be flat, full on charging at 30 amps up until the very end when it would start to taper off and the charging would end at 25 or 20 amps.
I’m not worried about setting the MaxV higher than the actual voltage I’m attempting to hit, as it is still much lower than my pack’s actual max voltage, and if something were to change with the pack chemistry making it miss the TermC cutoff, the MaxV would still stop the pack from reaching 100% charged. (and the termination timeout would eventually hit.)

This is the end of my main thought, but you can continue reading for…..

Extra Info about my pack, charging to the 80% level, etc…

The 48 modules from my Nissan Leaf battery pack (LMO/LNO chemistry)  are arranged in a series of sixteen sets of 3 parallel cells. This gives me a 180Ah battery with an absolute maximum voltage of 134.4 (4.2 volts per cell). In actual use the 4.2 VPC level should never be reached, if you charge the cells to 4.1 volts per cell they are around 99% charged. As the extra 0.1 volt difference between 4.1 and 4.2 doesn’t really buy you much extra capacity,  most people use 4.1 volts per cell (131.2 volts) as a safe “full” or 100% capacity on the Leaf Cells.  My Mini-BMS units will start to shunt voltage at 4.1 VPC, and raise an over-voltage alarm at 4.2 VPC.

However, if you charge the cells to 4.0-4.01 VPC (128-128.5 volts) that corresponds to about 80% of their maximum possible capacity. To maximize cell and battery pack life, you want to minimize the time the cells are fully charged or fully discharged. If you can keep the cells between a 10%-80% state of charge (SOC) it will maximize their battery life.

Keeping them above 10% SOC is easy…don’t drive until they are empty. Keeping them at or below 80% SOC is also easy, simply turn off your charger when they are only 80% charged.   This is why the early Nissan Leafs had the option to only charge the battery to 80%. (Removed in the newer Leafs due to EPA regulations on how maximum range is calculated.)

If you want the extra 20% of range that charging to 100% SOC would give you, it is better to charge to 100% and then immediately discharge the pack by driving it (as opposed to leaving it sitting at 100% charge all night).  This is one reason why Nissan Leaf’s have a charge timer, so that you can tell the charger to finish just before you start your daily drive. (The other reason is so that you can tell it to start charging only after the low cost nighttime electricity rates start, if you are on a time of use metering rate plan.)

My 2nd charging profile will be a 4.1 VPC full 100% capacity charge, for when I feel the need to really go long distances. (or to get the pack ready for a top balancing equalization charge, my future 3rd charging profile.)

Driving down the road today I smelled a plastic/electrical burning smell, which caused me to stop the truck and run around it quickly checking for any problems in my new Leaf modules. After verifying that they were not on fire, smoking, bulging, or even warm, I sniffed around the truck and decided the smell was emanating from under the hood, and eventually traced it to near my DC-2-DC converter (which keeps my 12 volt accessory battery charged up from the main 128 volt pack, replacing an alternator on an ICE vehicle). When I checked on the accessory battery voltage, it was 13.8 volts instead of the 14.5 volts that normally shows up when the DC-2-DC converter is working, so I thought that I had blown that out.

As it turns out, the only thing that had melted was the leg of the 30 amp 12 volt fuse I have between my DC-2-DC converter and my 12 volt accessory battery. Note: the fuse did NOT blow. One leg of the fuse melted into the holder, melting one side of the fuse and the plastic holder. The DC-2-DC converter was still working (but no longer connected to the 12 volt accessory system), and all of the 12 volt components were working fine on the redundant battery power.

At the time this happened I had the headlights and fan blower on, so the 12 volt load was about as high as it gets, but I’d been driving around like that for several years without the fuse or holder giving me any problems.  The only explanation I can come up with is that the process of moving wires around for the Leaf Module install loosened up the fuse in the holder and caused a loose connection, and the added resistance heated the connection up until it failed. (Although the fuse looked to be fully inserted into the holder even after it melted…)

I will have to replace the fuse and holder, and I’ll probably zip tie the new fuse into the holder when I replace it.

My truck’s charge controller supports the J1772 protocol, and I have added a J1772 inlet I took out of the same salvage Nissan leaf that provided my LiIon battery pack.

I added the J1772 port, the “start charging” button, and a rotary switch to select between different charging profiles, as well as a 120 volt, 15 Amp RV inlet behind a flip up license plate.

When you have one charging inlet, things are simple and safe. When you have more than one, things can get complicated. In my case, I wanted to use the same charger(s) with both inlets. But I shouldn’t just wire them both up in parallel, because that would mean that the (male pins on the) RV inlet would be energized at 240 volts when charging via the J1772 plug, and it wouldn’t be good for somebody to reach in and touch them. Also, if somebody were to try and plug in the J1772 AND a 120 volt extension cable at the same time, they would be connecting a HOT (from the J1772) line directly to the Neutral line on the 120 volts (causing a short circuit). [Having the J1772 inlet energized with 120 volts is also undesirable, although slightly less dangerous, as the J1772 inlet is designed to be “finger safe”.]

To solve these problems, I used a large power relay rated at 30 amps to switch between my two possible power sources (J1772 & 120 volt RV inlet).The chargers are connected to the common power connector, the J1772 inlet is connected to the normally closed contacts, and the 120 volt RV outlet is connected to the normally open contacts (and the coil switching relay).

By default, the J1772 inlet is connected to the chargers. (For this application it is important to find a relay where BOTH the normally closed and the normally open contacts are rated at the full amperage, many “30 amp” relays are only good for 1-5 amps on the normally closed contacts and the 30 amp rating is only on the normally open contacts. Note that my chargers max out at an 18 amp draw at 240 volts, so 30 amps gives me a good safety margin. If I had a charger that could pull a full 30 amps I would have gone with a 40 or 50 amp relay.)

If anyone plugs a live extension cord into the RV inlet, it switches the relay (disconnecting the J1772 and connecting the 120 volt RV inlet). Even if the relay fails open or closed, only one of the two inlets is connected to the charger, and the other inlet is disconnected from everything.

The second 120 volt relay is used for “signaling” wires to control my EVCC. One side will disconnect my ProfileSelect wire from the rotary switch on the front air dam, automatically selecting the 120 volt 12 amp charging profile (due to infinite resistance to ground). The other side grounds the “Proximity” wire from the EVCC, telling it that a (non-J1772 compliant) power supply is attached. In this setup, the EVCC will direct the two chargers to only draw 12 amps of power, which is the maximum safe continuous current draw from a standard 15 amp 120 volt outlet. [It also supports “drive-away protection” which can prevent the truck from moving away until all of the charging cables are unplugged.]

This photo shows the 120 volt power wires, with pigtails that will lead off to the switching coils on the power and signaling relay.

Basically, I’ve tried to make the 120 volt plug as “idiot proof” as possible. If you plug an extension cord into it and press the “start charging” button, the truck will charge at the appropriate rate regardless of how the rotary switch on the front air dam is set.

The low beam in one of my headlights burnt out, and since it’s a 4×6 sealed beam unit, I have to replace the whole thing. I decided to replace both the driver and passenger side at the same time so that they match, and upgrade to LED units by GENSSI (4×6 G3) that also add the ability to have always on daytime running lights (DRL). (As opposed to always driving around with my low beams on.)

The (1995-1997) Chevy S-10 only has two headlight units and the factory sealed beam headlights (H6545) use a weird plug shape that is not the standard H4 (the ground plug is twisted about 45 degrees). They are rated at 65 watts on the high beam and 45 watts on the low beam, but for nighttime driving I have never been happy with their light output.

The GENSSI (4×6 G3) that I am replacing them with has a measured power consumption for one unit at 14.4 volts on my bench power supply of 1.8 A for high beam, 1.03 A for low beam, and 0.08A (8ma) for the DRL.  This works out to 26 watts, 15 watts, and 1.1 watt for a single unit. The eBay auction page claimed 25, 20 and 1.1 watts for high/low/DRL, so the measured figures mostly match the online specifications, giving me hope that the specified lumen ratings may also be somewhat correct (Claimed at 2150/1800/57 lumens).

These units cost me $40 each, compared to the  $15 replacement cost for a direct drop in Wagner H6546.  However, the cost didn’t stop there, as I needed to pay an extra $30 for two adapters from the OEM socket to the H4 plug on the LED headlights. I could have just cut off the OEM connector and wired in a H4 socket for less money, but I decided to pay for the adapters to make the installation plug and play as well as retain backwards compatibility. Supposedly LED lights should last practically forever, but if I ever need to replace them in a hurry I want the ability to go back to the OEM 4×6 units which can be picked up at most auto-part stores.

The difference between the LED’s and the original headlights is quite apparent, as the LED’s are a “cooler”  color temperature (white, not yellow) and brighter, which is why I am changing out both headlight units even though only one burnt out.

Here you can see a comparison of the new LED on the left and the original halogen on the right, shining on a garage door in the day and at night.

I paid an $80 premium for the LED lights as opposed to the cheap OEM halogen replacements. For that $80 I get a cooler color temperature (for a more modern look), more light (better nighttime visibility), minor energy savings,  and the ability to wire in true daytime running lights if I decide to make the effort (not yet connected).

As I was accelerating across a road in my S-10 EV, I heard a pop, and I lost power. I was able to coast to the side of the road, and use my small “glovebox” multi-meter to determine that the HV fuse was blown. The real question was why did it blow?

Given that the leads from the batteries were still providing 128 volts, the fuse probably blew because the motor or controller had drawn a lot more power than they were supposed to. With the advice of members on the EVDL, I was able to use a 60 watt lightbulb connected to some lamp cord to determine that the controller was not shorted and appeared to work.

Specifically, I replaced the fuse with the 60 watt lightbulb, disconnected my motor from the controller, and turned on the keyswitch. The lightbulb lit up as the capacitors in the controller charged up. It was supposed to turn off after this if the controller wasn’t shorted open, but it didn’t. However, I then realized that my DC to DC converter was in the circuit and drawing power, explaining why the lightbulb had stayed on.

I pulled the fuse to remove the DC2DC converter from the circuit, and then the lightbulb would light up as the controller charged it’s capacitors, and then go dark once the current stopped flowing. This meant that the controller was not immediately blown and shorting upon startup, but I had to test if it would short when activated.

So I replaced the high voltage fuse with the spare in my glovebox, and left the motor disconnected. I placed the 60 watt light bulb where the motor would be connected, and then powered up the system. By using the “go” pedal, I was able to use the motor controller to power up and control the voltage and brightness of the lightbulb. This showed that at least under low loads the controller was working correctly, so I moved on to diagnose the motor. (See my next post for that…)

As things turned out, the controller WAS the source of my problems. Apparently, some number of the MOSFETs inside had shorted out, destroying themselves and causing my fuse to blow.  When I tested it with the lightbulb, the destroyed MOSFETs were no longer shorted (it’s hard for something that exploded to maintain a short), and the controller was only”working” on a few remaining MOSFETs. (Plenty to control a 60 watt light bulb).

But, since I didn’t know that yet, I continued on to checking out my ADC FB1-4001A motor.

After my high voltage fuse blew, I used a light bulb to make sure that the controller was not shorted and appeared to work (controlling 60 watts). [As it turns out, some of the MOSFETs in the controller had failed, but it would still work for low current draws; Where low is defined as 100A or less…more about that later…]

I thought that perhaps the motor was shorted out, as the motor resistance was only measuring 0.2 ohm, but it turns out that series wound DC motors do have low resistance, so this didn’t necessarily indicate a short circuit in the motor.

I replaced the expensive HV fuse with an inexpensive sacrificial fuse (18 ga lamp wire), then put the transmission in neutral and tried to spin the motor under no load. (I should have tried to turn the motor by hand, or by pushing the truck in gear just to see if it was free, but I didn’t think of that at the side of the road.)

I had a fire extinguisher and open water bottle standing by when I tried to spin the motor with no load, but all that happened is that my 18 ga wire flashed and disappeared with some smoking insulation. It is likely that I just needed a larger wire to handle the startup current (I was hoping that the capacitors in the controller would help out with this), or it may be that more MOSFETS’s in my controller died at this point.

So I gave up on the idea of driving the truck home with a replacement fuse, and we towed it home and I got started checking the motor over to try and see if it was pulling excessive current and was responsible for the blown fuse.

Here is a list of the items I checked, in the order I found them convenient to do :

• Could I turn the motor or was it physically seized up?  I was able to roll the truck backwards while the transmission was in gear, so the motor could physically turn.
• I also turned the motor by hand (using the front shaft) with the transmission in neutral to make sure it was easy to turn and didn’t have any rough spots.
• I connected a multimeter to the motor terminals as I turned it by hand to see if the resistance goes up or down as you turn it (looking for a big spike down to indicate a short). On my motor, the lowest resistance was 0.2 ohm, and the highest was 0.5 ohms. (While actually in motion I would get a negative ohm rating as the motor generated a small amount of current/voltage, so I had to stop every 5-10 degrees and let the reading settle.)
• I checked the resistance from the + and – motor leads to the case of the motor (without disconnecting the cables on all the terminals) to check to see if there was a short. (They were both out of range, no connection on my meter.)
• I had been advised to disconnect the cable to all four of the motor terminals and check the resistance from each of the four terminals to the case, but since my motor +/- cables are connected in series with the other terminals I figure that if any of the terminals were shorted it would show up with the +/- resistance to case check. (I’ve been told that the measurements should be in the mega-ohm range when the motor is new, and may creep down as low as  the 30 kOhm range after brush dust builds up. If it gets this low the motor needs cleaning with a motor cleaning solution you can buy at a motor shop.)
• Checked the insulation on the motor cables to make sure that it had not frayed and shorted to the chassis of the truck or motor.
• Visually inspect the brushes and commutator while turning. They had some wear, but looked to be working fine.
  
• Finally, I tried powering the motor (while disconnected from the driveshaft!) from a 12 volt auto battery (needs a lot of amps to get started) with some jumper cables. (Connect to the battery terminal last so the spark does not hurt the threads on the motor terminals.)

At this point, my motor spun just fine, had no visible arcing or unusual noises or rattles, so I decided that the motor itself was fine, and my fuse failure was due to something else. My thinking at the time was that it was simply age and vibration, combined with the extra amps that my new lithium ion battery pack can provide. So I decided to put everything back together and take it for a test drive with a new fuse. [More on how that turned out below.]

FYI – The Curtis controller current limits at 500 amps, but my old lead acid golf cart battery pack would typically never provide more than 300 amps, while the Nissan Leaf Lithium battery pack is happy to provide more than the full 500 amps.)

If the motor spin test hadn’t worked, here are a few more steps that I would have performed to try and isolate what was wrong with the motor.

• Pull all of the brushes out so they don’t contact the commentator, then re-test the resistance from the motor terminals to the housing. If it reads no connection, the field windings are OK (not shorted). If you get a reading here, it indicates which field winding is shorted to the case (possibly just by dust…)
• Insert each brush back into it’s holder one by one (only one inserted at a time) and check the resistance of that brush to the motor housing (should be no connection).

However, the motor appeared to be good, my controller had tested good with a 60 watt light bulb, so, on to the road test!

How I blew up (the rest of) my Curtis 1231c-8601 controller:

Having verified that my motor spun just fine on 12 volts, and that my controller could control a 60 watt light bulb with no problems, I figured that perhaps my 10+ year old fuse had just blown due to old age. So I replaced the fuse, and used the controller to spin the motor in neutral, which worked just as well as the 12 volt battery.

So I decided to go on a test drive, and pulled the truck out of the driveway. It drove normally at slow (< 15 mph) speeds, but when I tried to accelerate to 30 mph I got some shuttering and pulsing that I would normally associate with the controller going into current limiting mode, and the truck had no real acceleration to speak of.  At this point I probably should have realized that the controller was half gone and aborted the test, but instead I decided to try and see if the truck could reach the speed limit, and after another thirty seconds of driving I lost power to the motor completely. (But my HV fuse had not blown.)

I figure that the controller had been limping along on a fraction of it’s original MOSFETs, and by driving it again I blew the remainder of them out. So, I have ordered a replacement (used) motor controller, and am hoping that it will get me back on the road relatively quickly.

After replacing the Curtis 1231C-8601 motor controller that had failed, I opened the case up to figure out what had failed.  The controller hardware is inside of an aluminum extrusion with both ends “potted” with some black semi-flexible material (hard silicon perhaps?) that could be cut using a razor knife and a lot of effort.

Inside, there is a Pi shaped piece of aluminum extrusion that acts as the heatsink for the MOSFETS and freewheeling diodes, as well as being electrically connected to the motor – terminal. It is held against a large thermally conductive, but electrically insulating pad, which separates it from the controller case, but allows heat to be dissipated. It is held in place with 8 screws that pass through insulating plastic brackets into the bottom of the case.

People online had told me that these screw holes were “potted”, but on my controller they were just filled with two rubber plugs.They also told me that you could not cut through the Curtis potting material with a razor knife. [This super hard potting material was also prone to cracking at the edges and letting moisture into the controller, so a flexible rubber like material is better anyways…]

So either my controller had already been opened up, or Curtis had decided to use rubber plugs for the holes and a more flexible potting material on the controller that I had. (There was a “Warranty void if seal broken” sticker on the front, and as far as I could tell the inside of the controller was completely stock, so I’m leading towards Curtis just using a different potting material, but it’s possible somebody may have already repaired it once using exact replacement parts and put their own warranty sticker on it. There were some markings inside that might be from the factory, or might be from a repair shop you’ll see photos of farther down.)

I removed all 8 screws and plastic bushings from the bottom, and then cut around the potting material “end-piece” on the front (terminal) side and pulled the entire controller unit out of the aluminum extrusion case.  Then I had to cut around the terminals and pulled the potting material off the front. It had some type of fiberglass panel between the potting material and the piece of black foam behind it.  I was not able to remove the potting material and fiberglass panel in one piece, so if/when I put it back together I’ll just have to re-pot it with black silicon.

Once the guts were removed, I could see a spot under the control board where some power electronics had fried.  [The common failure mode for these controllers is for the MOSFETS nearest to the logic control board to blow up, because they turn on just slightly sooner than the other MOSFETS due to the propagation delay of electricity through a wire.]

I had to unsolder the 7 connections between the logic board and the power board (as well as a 2 wire thermocouple) so that I could remove the logic board and see the blown power electronics. The immediate problem was not hard to spot…

Curtis 1231c-8601 power board components

The Curtis 1231c-8601 power board is relatively simple. It uses 18 MOSFETS in parallel to switch current from the motor- terminal back to the battery- terminal (the motor+ lead is already connected to battery+). The MOSFETs it uses are IXYS IXTH50N20 SP9536 chips. The center lead is bent up over the chip and soldered to a ring terminal, such that the screw that attaches the chip to the heat sink also electrically connects that pin to the heat sink.  Most chips that attach to a heatsink have a metal back, but the IXTH50N20’s used here do not, so it appears that they had to take extra assembly steps to electrically couple it to the heatsink. The power MOSFETs have  a 47 ohm resistor on their gate drive line. Such a high value was chosen to deliberately slow down the switching of the MOSFETS, so that the ones nearest to the logic circuit would not be able to turn all the way on before the ones farther away had a chance to shoulder some of the load. It would appear that this strategy was not entirely successful, as the closest MOSFETs blowing up is a common failure mode.

Near each MOSFET is a freewheeling diode (used to conduct current between the motors +/- terminals when the MOSFETS are not conducting current from the battery. They are TSR2402R 7103 K units, which basically have two sheets of metal with a round diode mounted between them. They are “reverse polarity”  Schottky diodes, which means that the anode is connected to the heatsink by the screw (as well as being connected to the power PCB by a lead. Unfortunately, they are difficult to source replacements for in this form factor.  Fortunately, they usually do not blow up like the MOSFETS.

Here is a bottom view of one of the failed MOSFETs:

One leg was completely melted. The arcing electricity actually ate some of the metal case of the diodes that were mounted next to the MOSFETS! (amazingly, these diodes appear to be still working.)

In addition to the obvious damage to two of the MOSFETs, I noticed a third mosfet that has some residue around it. Although not as obviously blown apart, this guy may have issues as well. In general, when one MOSFET in the set blows up, you should replace them all, as others may have been overstressed and ready to fail.

Also, a trace on the logic board has been blown away. If you look at the four wire connector just to the left and above the white “ORB-102 w/o 60355 rev.M” sticker, you will see that the second pin from the right leads to a trace that has acted like a fuse. Arcing electricity probably got it. There were also a few traces on the power board that will need to be fixed.

Here are a few shots of the Pi shaped heatsink showing where all the MOSFETS and diodes were attached on one side and the soot pattern.

I should also mention that the 1231c has the option to “plug brake” (more for forklift operation than on-road vehicle usage) and has six plug braking diodes connected to an A2 terminal that is unused in my application. I just unscrewed the entire connector assembly and A2 terminal, and will probably not bother re-installing it as I don’t need it.

I found a few hand markings inside the terminal. One was the “OV 174” pictured above, and the other was this “CIL / M1” on the cardboard shield that fit between the power electronics and the logic board.

In addition to the MOSFETS and Diodes, the power board also has 35 capacitors used to reduce ripple as the MOSFETs switch. They are Nichicon 220 uf 200v electrolytic capacitors.

There was also one other component attached to the heatsink (but electrically isolated with a silicon pad). it was a Vishay IRFP254 532P power MOSFET at location Q13.

This MOSFET is used as a 24 volt voltage regulator to power the logic part of the circuit

My Curtis 1231C motor controller blew up some MOSFETs and died. I replaced it with a used unit to get my truck back on the road, but now I’m interested in repairing the one that died so that I’ll have a spare.

I might be able to replace the components that died with exact replacement parts (but the IXTH50N20 MOSFETs are hard to find nowadays, and the diodes are basically unobtainable) to get it working, but since I have it open and am doing all of this work, I am exploring alternative (new) components that will have higher ratings and possibly give my controller more capacity or at least more resistance to blowing up again.

Of course, if I replace one component (power switching MOSFET, freewheeling diode, or ripple controlling capacitors), I will probably need to upgrade the other two as well so that I don’t just move the weak link from the MOSFETS to the capacitors or diodes.

Power switching MOSFETS

The original part used is IXYS IXTH50N20, which has a 200 volt maximum rating, 50 amp switching capacity (200 A pulse), and a resistance from source to drain when on Rds(on) of 0.045 ohms (45 micro Ohms). The total gate charge, Qg(on), is 190nC typical 220nC max.

(All packaged in a TO-247 AD case, with drain on the tab connected to the heatsink and Motor – rail.)

An “upgrade” component recommended by David Mosher  is the IRFP4668PbF, which retains the 200 volt maximum rating, but has a 130A maximum switching capacity (520A pulse). The Qg(on) is 161nC typical and 241 nC max. This is close to that of the original part, which means that the 4668 won’t turn on much faster or slower than the 50N20’s.

The 4668’s  have a much lower Rds(on) of only 0.0097 Ohms (9.7 micro Ohms), which is five times smaller than the 50N20’s. This is good in that it produces less heat (probably 5 times less heat!), but it does have a side effect I would have to work around.

The Curtis logic control board measures the Rds(on) of the MOSFETs under load and uses that as a shunt resistor to detect how much current they are switching. If the Rds(on) of the MOSFETs are lower than the logic board is expecting from the IXTH50N20 parts, the logic board will think the current is much lower than it actually is. This will prevent the controller logic from entering high-current cutback mode unless I can adjust the sensitivity of the current sense circuitry to match the new MOSFET’s value.

The logic board does have a factory set “c/l set” pot, as well as a user adjustable C/L adjust pot, so perhaps by messing with these pots or changing out a resistor I can keep the current sense circuit happy, but it will mean that I will need a way to accurately measure the current in a high power situation, which probably means testing it in my truck….

I like the possibility of making less heat, because a cooler running controller is good for reliability. I also like the fact that the amp rating is much higher, which will make them less likely to blow up, and possibly give me greater performance (if I’m brave and foolhardy enough to make use of it). I don’t like the fact that the maximum voltage rating is still 200 volts. It’s hard to find MOSFETS much higher than this, but I’ve found some 250 or 300 volt units in the 100 Amp power levels.

Normally I wouldn’t worry about increasing the voltage range above stock too much (as my Nissan leaf battery pack is at 134 volts maximum), except that I believe I have found a good replacement for the diodes that are 600 v rated, and I may be able to upgrade the capacitors to 250 volt rating. So having a MOSFET rated to 250 volts minimum would be preferable.

One I found is:
IXTH110N25T

MOSFET N-CH 250V 110A TO-247
250v, 110a, 24 mOhm RdsON
Qg max = 157nC

The Diodes:

The stock diodes in my Curtis are marked “TSR2402R”, and others have said that Curtis used “MR2406FR” (24 amp, 600 volt, 1.15 Vf max,  250ns) or “SR4180R” freewheel Schottky diodes. (I’ve seen one reverse engineered schematic Marked 24 Amp, 200V, 300ns).  They are in a TO-220 style case (it’s actually a button tab-mount diode, which is a button diode mounted between two metal plates or tabs that form the legs, but the same size as a TO-220 case. The rear metal plate is screwed to the heatsink. Finding replacement drop in diodes for the Curtis controllers is what most people say is the hardest part of a rebuild.

The key aspect of these diodes is that they need to be “reverse polarity”, with the anode connected to the tab (rear metal plate), so that they can be bolted to the M- rail/heatsink without blowing up. A drop in replacement is the “MUR2020R”, but their current rating and max voltage is low  ( 20Amp, 200V, 0.97Vf, 95ns).

[As a side node, there are 18 of these diodes in parallel, so 24 * 18 = 432 amps, which feels low for a 500 amp rated controller, even if their peak repetitive current rating may be twice that.]

(David Mosher uses  APT100S20BG diodes (200v, 100A, 0.89 Vf, 40ns), which are not reverse polarity, and insulates them from the heatsink with a silicon pad and connects them with wire extensions).

One option I found is the DIOTEC 7500 line. I’m specifically looking at the DIOTEC 7506R, because it is a 600V rated component available in reverse polarity in the TO-220AB form factor. (75A, 600V,  1.35 Vf, 150ns).

In addition to the generous 75A average forward current rating, the peak forward surge current is a whopping 800 amps! The only downside is that the forward voltage, at 1.35 average, is slightly higher than the 0.97v from the MUR2020 or 0.89Vf of the APT100S20BG’s, but it is close to the original 1.15vf of the MR2406R units.  This means that the diodes will produce slightly more heat than stock. (But, if the MOSFETS are producing 1/2 to 1/5 of the heat, the total heat will be lower overall.)

As far as I can tell, none of my current diodes are broken. (Some of them have pieces of metal burnt off of their metal tab mounting case from arcing that occurred when the MOSFETS blew up, but my meter reads fine on all of them, so I think this is mostly cosmetic damage.) However, if I can replace them with 600 volt units that have a much higher amp rating than stock, it seems like I should go ahead and do it while I’m replacing everything else.

Aluminum Electrolytic Capacitors –

I believe that the aluminum electrolytic capacitors in my Curtis (for ripple control) are also working fine and undamaged. There are 35 of them on my power board, and they are 200 volt, 220 uF (micro farad) PS(M) Nichicon capacitors marked 105 &deg; C and H0735. They are approximately 1.6 inches (41mm) tall and 0.71 inches (18mm) in diameter, with what looks to be a 7.5mm lead spacing.  [ I found an 18x40mm 220uF/200v in the PS(M) datasheet, code 2D 515.  The 7.5 mm lead spacing matches up with the 18mm diameter.]

They are rated to meet specs after 3,000 hours of operation (with 22K miles, I estimate I’ve put 750 hours on them). They are also rated to perform to specs after being stored for at 105 ° C for “1000” hours (41 days), but I don’t know how that corresponds to calendar life when stored at ambient temperatures for 10 years. They had a DF (tangent loss angle), a measure of ESR of 0.15.

Electrolytic capacitors can fail due to calendar age, and if I’m upgrading everything else to higher voltage rated components, I may as well investigate upgrading the capacitors. However, higher ratings with capacitors almost always equate to larger case sizes, and I can’t fit anything larger inside the existing Curtis case. Finding capacitors with a 220uf or greater rating with a voltage higher than 250 in this form factor may be difficult due to the laws of physics, unless I decide to change from electrolytic to a more exotic (and expensive) composition.

My top choice for replacing them would be
Panasonic EEU-ED2E221 (P13533-ND) $3.94
220uF, 250V, 10,000 hours

It has the same capacity, the same DF (0.15), but a 250 volt rating, and 10,000 hours rated life.

Alternatively, I could go with an upgrade on the capacitance to 330 uF, but retaining the existing 200 volt maximum with:

Panasonic EEU-ED2D331 (P13524-ND) $3.94
330 uF, 200V, 10,000 hours

I’ve been told that upgrading the capacitance won’t buy me much from a performance or lifetime standpoint, so I’m leaning towards upgrading the maximum voltage to the 250V version.

The inexpensive option is basically the modern replacement part from Nichicon, with an upgraded 8,000 hour service life rating:

Nichicon UPW2D221MHD (493-2013-ND) $2.14
220 Uf, 200V, 8,000 hours

The difference in cost ($2.14 * 35 = $75 and $3.94 * 35 = $138) is about $63, if I were to buy them from Digikey (just about the most expensive place to buy electrical components…)

I am looking to replace the MOSFETS, diodes, and capacitors in my Curtis 1231c with upgraded components. I unsoldered one of the existing TSR2402R (7103 K) diodes from the power board and tested it with my Fluke meter and bench power supply.

Here are my results:
Power Supply providing 3.2A, forward voltage drop: 0.776 volts
Power Supply providing 2.0A, forward voltage drop: 0.737 volts
Power Supply providing 1.0A, forward voltage drop: 0.697 volts
Fluke Diode Setting: 0.351 vdc

Average time for the button temperature to raise from 25 °C to 50 °C with a 3.2A current: 45 seconds

The replacement parts I purchased were from DIOTEC, specifically their DR7506FR model (the R at the end means “Reverse Polarity”, making them an exact drop in replacement in form factor and polarity). They were marked: “DT110  DR7506FR” plus a diode schematic. Here are my results for the upgraded component:

Power Supply providing 3.2A, forward voltage drop: 0.754 volts
Power Supply providing 2.0A, forward voltage drop: 0.700 volts
Power Supply providing 1.0A, forward voltage drop: 0.646 volts
Fluke Diode Setting: 0.399 vdc

Average time for the button temperature to raise from 25 °C to 50°C with a 3.2A current: 47.5 seconds

Of course, the original diode I’m measuring had been in use for many years (I estimate ~750 hours of driving time given the 22K miles) and was heated up as part of the soldering and unsoldering process, while the DR7506FR I tested was brand new straight from the manufacturer. After I unsolder a few more diodes I’ll check them to make sure their readings are similar. (I’ll probably also test a few other DR7506FR diodes from the bag as well.)

Of all the measurements, the temperature rise time measurement was the least scientific, as I was using an inexpensive non-contact IR thermometer and attempting to point it at a small button in each diode, waving it back and forth to find the hottest temperature. I took 4 measurements on each diode (alternating to let the other one cool down) and averaged them together. In general, the readings from the DR7506FR were longer than from the original TSR2402R with one exception. If I throw out that pair of readings, the averages would be 46 seconds vs 50 seconds. Given that the measured forward voltage drop for the DR7506FR was lower for any real amperage readings, it dissipating less power and taking longer to rise to 50 °C appears to be reasonable.

I desoldered all of the main power components (diodes, MOSFETS, capacitors) from the power board of my failed Curtis 1231c PWM DC motor controller. The plan is to upgrade all of the components to give it higher capacity; while producing less heat. Of course, to replace them, I had to remove the old ones, which took around 6 hours of work with two different soldering irons and a solder sucker.

My advice:
-Heat component legs (diodes/MOSFETS) from the top of the board (side with the component) while you solder-suck from the bottom. Get one leg completely free first, then work on the other. After you suck almost all the solder out, you may still need to re-heat the leg and push it away from the PCB with a small screwdriver so it doesn’t stick to the inside of the hole.
-For the capacitors, don’t be afraid to add a little solder to the smaller leg, and then use a 100 Watt super wide tip soldering iron to heat both legs up at the same time, and pull the capacitor straight out. Suck the solder from each hole individually later once all the components are gone.
-I heartily recommend the Engineers SS-02 Solder Sucker, the silicon tube it uses is great! I did get solder stuck inside the metal tip a few times, but nothing a 5/64th drill couldn’t fix right up.

Here are a few photos of the process, with a nice video at the bottom:

This photo shows a little bit of the carbon soot left over after two MOSFET’s blew themselves up. I’ll be cleaning all of that up before re-populating the board.

I am upgrading the power board of my Curtis 1231c DC PWM motor controller. It uses 18 MOSFETs to switch the power, and each MOSFET had a 47 ohm resistor on it’s gate input. The point of such a high resistance was to slow down the switching of the MOSFET’s so that they would all share the current somewhat equally and no single MOSFET would turn completely on before all of the others had a chance to start shouldering the load.

The Curtis 1231C typically fails with a few MOSFET’s closest to the logic board vaporizing, probably due to switching on before the others, as the distance to the logic board is the smallest.  This is due to the poor PCB layout which has some MOSFET’s much closer to the logic board than those on the other side of the board. The 47 ohm resistors counteract this somewhat, but the slow switching leads to extra heat and less efficient operation, as the resistance of the MOSFET while switching is higher than when it is fully on.

The replacement MOSFET’s have a higher maximum amp capacity than the components they are replacing, so I am hoping they will tolerate a slightly faster switching time. When replacing the 47 ohm resistors, I purchased 35.7 ohm, 1/2 watt, 1% tolerance resistors, and then binned them. I placed the resistors with the higher resistance closer to the logic board, in the hope that they will counteract the propagation delay due to the circuitous routing on the PCB.