Gem a.c. motor conversions 8kw motor

We have it working pretty well. @MikeKC
It should be time to start a public thread on installation and tuning. Mike found that the 8kw motor fit in his Gem with only slight interference to a shock coil.
First test shows 42mph @ <7800 rpm. 12:1 gears.
He is using an interface board to connect the new control to the Gem harness.
Version 2 is in progress that will add some protection diodes, and corrected logic for F-Turf-R oem switch.

@Troyin909 did all the initial work. We are just cleaning up some loose ends.

Our goal is to have a partial kit available for <$1500
Motor and controller.

Grant has a motor on the way. It may not be applicable to most of us, as it’s going in a 2016 model.

Yes David, Time to start letting a little info out. Still a lot to be fine tuned.

  1. Motor will fit WITHOUT modification (2005 - 2014). You need to remove the passenger side shock to allow the motor to slide in, once the motor is in place the shock can be placed back in the stock mounts.
  2. I am seeing ~42mph on 23" wheels/tires at 7800rpm/12:44 gears - working toward 8500/8700rpm
    2a. I was able to run 42mph up a 20/25 percent grade and not loose any mph, long steep hill no issues.
  3. Stock GEM F/L/R switch should work when we are done.
  4. Turn signals and battery meter still work as does lights/horn/ and PB buzzers.
  5. Gear selection/turtle/wrench on LCD flash - currently working on a fix for this.
  6. Working on full replacement touchscreen LCD in stock location with speed/battery/turn/rpm/motor temp/controller temp. This is a secondary project.
  7. Speedo is non-functional at this point, again working on a fix.

What’s it looking like for those of us with older (2002) cars? What battery are we working with. Thanks.

Very interesting,nice job

Everything should be about the same. Check clearance of a longer motor. 14"long. Let me know if you want to follow along.

Yes, I’d like to follow along.

it is likely that on a 2002 you will need to move the passenger shock a little bit. We are gong to test fit one shortly so we will know, should not be a major issue.

That’s great Mike. Planning on beginning a teardown this winter anyway. Currently running FLAs, killed the last new batch (didn’t plug in) so was planning on lith or similar upgrade. What works best for this motor?

Also interested to follow along this AC conversion

Sorry all, it has been a really busy week. I will be posting up more information soon.
@IRBGEM - I think I have two friends that are going to do this upgrade, one on a 2000 and one on a 2002 so we should get some good experience.

You should be able to run the stock battery setup with the new motor and controller. We did some testing at 70v and it was awesome.

We all run 98.8v lithium (me and my friends) and you can leave burnout marks if you are not careful :slight_smile:
Getting ready to drop a Tesla battery module in mine.

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I agree. Seems to work fine right now at stock voltage. I guess there are some tuning issues at 98v.

We are developing an interface board that will allow using the oem wiring harness, and plug into the new control. Working now, but I cleaned up a few things on a new version pcb.

Hope they will be here for more testing in a couple weeks.

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How’s the range / power consumption looking compared to the DC motors?

No definitive test, but I’m guessing double the range at the same performance, or double the performance at the same range.

I think this is a very conservative preliminary estimate. 50ah battery in my hotrod golf cart spins the tires, 35mph+, better range than original.

@MikeKC has some early adopters on the hook. Real users under real conditions will tell.

Parts are available now for DIYers. (tinkerers)
8kw cont. rated motor. 30hp peak power input. Calculated using 350a @ 72v
S4-350A or S6-550a Gen4 controller. Pre-programmed to run. Upgrade-able as we add features/modes.

3 modes available. We can use input on what they should be. Econ, power-speed, hard regen, etc.?

There will be at least three of us available to customize driveability. Ca. Troy, KC Mike, Mn. Myself, possibly Grant.
Florida Michael may get on board as we get moving.

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Thank you @MikeKC and @Inwo for the updates. I’m at the point where I either throw down for a newer car or go for broke with the older one. I am getting new FLA’s (under warranty) this week and am planning on doing a host of repairs through March so I’m keenly watching this development you guys are working on. Sounds pretty exciting.

@Inwo Do you have any more Lifepo4 batteries on the market? Might sell off the replacement FLAs and go that route.

Yes, I do…
Wish someone was near me. I have a new set of lead batteries that came with a car.
These are really new. Not the wink wink, only a few months old.
They were purchased this month for a car destined for Florida. The new owner of this car found that the 6’ wide “Anvil” was to wide for community rules. So I took it off his hands.


Top secret Gem picture.


I see what you did there.

Need burnout pics or video!

Won’t be doing much testing today, 32 degrees, 50mph winds and snow flurries. I guess it will be a good day to stay inside and stare at the programming settings…

Same weather here, except for high winds coming later.
Barb hit heavy rains overnight, but good driving weather all the way.
I hope the Anvil doesn’t melt. Totaly disappointed in the seller. :frowning:
Tires were low, poorly strapped to trailer, trailer was tight and rubbing on fenders. Broken tail light.
Scratched from his previous tow. He said that he hauls classic cars which seemed safe.
Could be worse, if Barb can’t keep wheel side down. Trailer follows like crap. He specifically told me that trailer towed great on his trip from Ohio. grrrr