openinverter forum

JNHEscher wrote: ↑Fri Nov 21, 2025 5:55 am I'm still open to other motor and inverter suggestions. I wanted to support OI logic boards.

Right now, the LDU is probably the most powerful option available at a reasonable price. Any of the newer EVs making more power are doing it with multiple motors, and more complex gearboxes.

I think it's just a matter of sorting out the right drivetrain/gearing selection for your use case.

What about looking at truck e-axles? I'm not sure theres much of a market yet but i think this may be your best bet to having something strong and reliable. The LDUs are powerful but not what I'd consider to be reliable. You may be able to adapt their inverter or another inverter to the eaxle.

P.S.Mangelsdorf wrote: ↑Fri Nov 21, 2025 12:48 pm Right now, the LDU is probably the most powerful option available at a reasonable price. Any of the newer EVs making more power are doing it with multiple motors, and more complex gearboxes.

I think it's just a matter of sorting out the right drivetrain/gearing selection for your use case.

Yeah, that's what narrowed my options down to the LDU. I can still easily fit two LDUs. Gets expensive, but most conversions do

jrbe wrote: ↑Fri Nov 21, 2025 4:42 pm What about looking at truck e-axles? I'm not sure theres much of a market yet but i think this may be your best bet to having something strong and reliable. The LDUs are powerful but not what I'd consider to be reliable. You may be able to adapt their inverter or another inverter to the eaxle.

I've been interested in those, but like you said, there's not much of a market yet. I think I would have to go through hoops of emails and a small fortune to acquire a set. Other thing that always bugs me about beam axles is the low-hanging differential. Where I drive my truck, I occasionally snag a stump or a rock. I'd hate to bash my motor or rip HV cables off.

Reliability is a toss-up, for sure. Even with Tesla's faults, I'm almost certain that their system (with the aftermarket fixes) is still far more reliable than the diesel drivetrain. My truck has the Navistar HEUI fuel system that craps out on a regular basis and the transmission has CANbus that blanks out at times.
Upside to where I plan to mount the LDU is that I would simply lift the bed and the full unit is right there and highly accessible.

I still intend to make this truck all-wheel-drive with locking or limited slip differentials front and rear. The increase in traction will be such an immense help.

Do you have a picture of what the rear axle looks like currently?
I can't really see it in the picture of the back. May help think of different ideas. I was thinking 2 motors if it's split..

jrbe wrote: ↑Sat Nov 22, 2025 12:20 am Do you have a picture of what the rear axle looks like currently?
I can't really see it in the picture of the back. May help think of different ideas. I was thinking 2 motors if it's split..

I don't have much interest in making modifications to the current drive axle unless doing so costs much less.

If I remember correctly, it's a Meritor. My size 10-1/2 boot for reference.

Keeping the build thread going.

Bus bars for the LTO cells showed up. Cleaned those up and fired up the EBC to top balance the cells. Wonder how long the three lead acids batteries in the truck will power this


Likely won't be until January that the first set of Winston 200Ah LYP cells show up. Once they do, they'll replace the lead acids. Hopefully they will encourage the engine to start again.

OI forum has been super buggy on my phone, so no pics. Got all the LTO cells balanced up and assembled into a 2p6s pack. Just need to finishing designing the case.

As far as the Tesla LDU setup with Quaife 4.5:1 ratio coming, running that with Oshkosh 6:1 axle drive and 42.3" tires, the Tesla motor would be spinning at around 11,800 rpm at 55mph. 70 mph would be spinning it at the maximum motor rpm. I don't think the LDU would hold up very long at those rates, considering a Tesla Model S or X LDU spins around 8,500 rpm at 70 mph.

I'm on to pondering what other motors and gears ratios to use. Likely something that OI doesn't have a logic board for, unfortunately.

There have been some big axial flux motors on eBay randomly, some can stack. May be worth considering depending on your gearing.

jrbe wrote: ↑Sat Nov 29, 2025 2:53 pm There have been some big axial flux motors on eBay randomly, some can stack. May be worth considering depending on your gearing.

I've seen those. May look them over again.

I did figure up the numbers for using the Tesla LDU motors adapted to my Oshkosh 55000 transfer case and they work out perfectly. This route may take me a long while to get accomplished.

12v LTO pack coming together. I need to continue drawing up the case to have 3D printed.


I'm about to start drawing a bus bar for this BMS so that a single 4/0 cable will bolt to it. Once the Winston 200Ah LYP cells come in, this will be the temporary 12v starting battery to hopefully get the engine to fire up again.

I do believe I will stick with Tesla LDU sport motors and inverters.

The Oshkosh 55000 transfer case that I have has a 0.99:1 high gear, 2.66:1 low gear, neutral, and an auto-locking center differential. Within the next few months, I plan to tear it down to start measuring parts and figuring out how I want/need to arrange them to adapt the Tesla motors to it.
The low gear in the t-case, combined with the TAK-4 6:1 ratio gets me 71mph at 9,000rpm. This also makes for 15,322ft.lbs. of peak torque, according to specs I'm getting from Westside EV. 1,272 peak HP as well. This is assuming that the peak 420 DC peak volts is correct.

I'll order a couple Tesla sport LDUs soonish. Right now is not the best time to expect expensive parts to get shipped. It's wreck city across several states due to winter weather.





Cooling these shouldn't much much of an issue, once I figure out the plumbing and pumping. The radiator currently in the truck is a full-aluminum aftermarket unit. The radiator fan tends to draw 40-50hp. I'll be getting rid of that fan and add some electric fans.




Also note that I cannot get the forum to stop turning my pictures sideways. This was a problem on two other forums that I frequent.

Fedex has my Winston LYP cells! Says they'll arrive this coming Tuesday. I'll have to measure the thread pitch and length for them, then start top-balancing.

I should have ordered enough bus bars to parallel all eight cells at once. Ah well. I'll make some short cables for the rest.

Posting for reference - 200Ah Winston LYP cells use 12mm diameter bolt with 1.75mm pitch and 22mm length.

Glad these cells are spec'd to function within freezing temperatures. Giving them 45 amps with the EBC, then I'll finish them off with a power supply.

Felt like going ahead and pulling the lead acid batteries out. 171 pounds of lead acid in total. The eight Winston cells are around 139 pounds.

Need to tidy it up a bit yet. Not the cleanest install, but this is intended to be relatively temporary. It's all hooked up. No communication from the BMS or any indication that it turns on yet.

I've decided that the 800-amp Daly BMS that I bought was a dead unit out of the box. No workie at all. Ordered a second one (sigh), and a couple JBD 300-amp 4s BMSs so that I hopefully have some chance of starting this damn thing. I'm anxious to start selling off the diesel parts.


Anyway - I've been randomly seeking what the absolute maximal DC input voltage is of the Tesla Sport LDU. WestSide EV states 420 volts. Somewhere, I'm fairly certain that I saw that the rating says 420 volts so that folks don't inadvertently fry the inverter with a few extra volts, but that it has a safety limit of 450 or 470 volts.

I'm not sure how tag members on here. P.S.Mangelsdorf, I saw your post in the wiki thread...
Tesla Large Drive Unit (LDU)
- includes motor, inverter, gear box
- rear motor in all RWD Model S and X 2012-2017
- Sport version was rear motor in all P variant Model S + X 2012-2017
- OEM Max DC voltage: 400V
- OpenInverter tested Max DC voltage: 410V?
- rated inverter component DC voltage: 600v?
- OEM Max amperage: believed to be 800-1200amps
- Open Inverter tested Max amperage: ? (Jon Volk, what are you running?)

The inverter can take an absolute max of 600v or thereabouts? If so, I'm planning to add more Winston cells in series to keep the amps down. Once I get more of my shed put together and organized, I plan to order two Sport LDUs to tear down and work on measuring for adapting to the Oshkosh 55000 transfer case parts.

600V is the absolute maximum of the IGBTs, you need to shave off like 30% to account for spikes. Also the capacitor on the DC bus has a lower rated voltage, 450V or so

johu wrote: ↑Thu Jan 15, 2026 8:01 am 600V is the absolute maximum of the IGBTs, you need to shave off like 30% to account for spikes. Also the capacitor on the DC bus has a lower rated voltage, 450V or so

I appreciate that. I'll bump the pack voltage up a bit. This will help even out the pack form and keep the cells at their voltage curve flat.

I technically have room for a second battery pack, giving me the opportunity to run two packs in parallel. This will help ease any major tress off of running a single pack.

Yeah, Johannes has the right info. (I think my post came from his or Damian's info in the first place)

I have a few LDU inverters torn apart but the parts are all in storage right now, I can double check this weekend. But from everything I've seen, I wouldn't push the LDUs much past 410V. I think you could probably get up to 420V, but beyond that seems way too risky to me.

P.S.Mangelsdorf wrote: ↑Thu Jan 15, 2026 12:59 pm Yeah, Johannes has the right info. (I think my post came from his or Damian's info in the first place)

I have a few LDU inverters torn apart but the parts are all in storage right now, I can double check this weekend. But from everything I've seen, I wouldn't push the LDUs much past 410V. I think you could probably get up to 420V, but beyond that seems way too risky to me.

Noted.

The Winston cells are still 3.2 volts nominal. I'll see where the curve flat tops out at before the charged knee (have a Victron Smart shunt on them). I'd like to add enough cells in series so that at full charge, they're sitting at the curve flat rather than the top of the knee.

I have a sport inverter phase sitting in my car that I need to look over more.

Been a minute. Tried two separate Daly 800-amp truck start BMS units that didn't work. Took that off and got my Victron Lynx and a smart shunt hooked up. The truck fired right up on the first try today.



Will be a while yet, but I still plan to order Tesla parts and tear down the Oshkosh transfer to start figuring out how I would like to adapt them together.