30HP Brushless motor upgrade on 2003 GEM

Wanted to share an upgrade I made on a 2003 GEM that I bought. The car did not run, so decided to get a brushless motor, which I am more familiar with from building ebikes.
The motor is a ME30-31001 capable of 22kW or 30HP.

It has a sine/cos encoder as opposed to the more common hall sensor, so went with Kelly KLS-8080N 500A

Excellent tutorial on how to wire/program this combo:

I had to remove the front battery support due to increase motor diameter, but it is shorter so won’t interfere with suspension.

Got it running and it is real torquey. Probably can spin the front tires.

The regen braking is great! Barely noticed that I only have drum brakes :stuck_out_tongue:

I will post more updates as I make progress.


Edit, sorry to hijack. But I’m excited about this motor on a Gem. I’ve been pushing it for years.

Actually unless you modified motor for halls, that is a PMAC motor.
Dang wish I knew you were doing this. You could have used Sevcon so we could trade files.
I have them on some of my hotrods. Trying to find someone to do more testing on a gem. Only one I know of was 5 yrs ago, and he didn’t like the rpm limitation of pmacs.

hotrod Zone

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Your car must have been a little different. @Troyin909 had to cut his lower A-arm bracket to make it fit. I’ll try to find his pictures.
One hell of a motor. Can peak close to 50hp on 96v.
It was a custom designed motor for a failed ev company. I’ve been buying their surplus stuff since they went under. Paired with 80v S6 Gen4 Sevcon.

Can’t wait to see how fast it can spin without overheating. (or grenading) :slight_smile:

Troy pictures:

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PMAC and BLDC are pretty much the same -they are both brushless. It’s only the encoder/controller that are different :stuck_out_tongue:

Yeah, didn’t know someone else had done this when I got the GEM over the holidays - only found out about this forum this week. I didn’t want to pay extra for a sevcon controller/programming/programmer from Electric Motorsport. Kelly has free SW so I can program it easily. The controller is $399 right now and the motor is only $750 - compared that to the $3000 kit + 3 months delivery time.

I also need to build a new battery. I’ve been testing with my 72V26Ah 20s10 Molicel 26p 350 A capable ebike pack, but will need a bigger pack for the GEM

I am going to build a 72V 100Ah 20s30p Samsung 33G - 300A capable ($1.8 cells from batteryhookup.com) So about ~$1500 with BMS and nickel/holders etc…

But first I need to fix the suspension with Progressive Suspension and beef up the rear axle…

No worries, glad to hear about someone else as excited about this motor as I am!

Yeah the 2003 is different. I saw his pics earlier. Did he ever get it running properly?

I got it to up to 32 mph on 72V - it could probably go a bit faster but I think that felt fast enough (my ebikes go 55mph).

No, could not run above 5000 rpm without overheating. I was not programming for him and did not know much at the time. Depending on gears 5000 is fast enough.
My hotrod is 12:1 with 18" tall tires and is faster than I dare drive it.
I did Tomberlin same setup, but S4 350a controller, on 48v ran just as good.

Went to a guy building a “jetson car” for burning man.

What voltage was it running at? I’m thinking I might go to 96V just to get that extra speed if I need it.

I don’t think extra V means more speed in the case of a PMac.
The noted limit of 5k rpm is more about the internal magnetic fluxes and fields flying around that heats the motor up.

The effects may be tuned out and more RPM gained with some creative programming. (That’s where you come in).

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Close to 96v as I recall.

John at Motenergy says magnet glue is engineered for 4500 rpm.
Many other factors involved, but they are low cost motors while they last. See what happens.

Yeah I’m running at 4500 rpm at 72, but the spec also says 6000rpm at 96V…

So I just confirmed with John as well and he says not to go above 5000 RPM. Maybe I’ll get larger wheels instead.

He needs to stand behind his products. I assume 5,000 is conservitive.
32 @ 4500 rpm. It will spin faster, no? What is limiting it? Common sense?
Or controller? I don’t know if your controller does field weakening. I’ve been told that fw is needed for more rpm.

If you want to use this motor as a brushless motor like E-bikes, I can link you to a guy who has installed halls in his ME3031. It is my understanding that brushless motor controls are inexpensive and common.

I have a 6:1 transmission that you can borrow. Another year old project with no takers.
It was a special build for me by @Old_Houseboater “touched by Rodney”. At considerable cost, but I am willing to take a loss or loan it out to get data.

Wow that would be awesome! Is that a drop-in replaced for a 2003 GEM?

More common but not much cheaper. For example Kelly sells the same controller that can work with hall or sin/cos encoder - need to specify at purchase. The motor/contollers are the same it’s just the logic that is different. I think you could use an Arduino to convert the sin/cos signal to generate hall like signal to get it to work with a Hall sensor controller. But I’m looking for a safe/reliable solution for my family to drive around town. So I’d rather get a more robust implementation :stuck_out_tongue:

Definitely add disc brakes to the front if you are seeking speed. Makes all the difference in stopping

Yeah, I was going to, but regen on this combo does most of the braking anyway (perk of front wheel drive), but need more testing at higher speed.

It was, but @djgabriel2004 had flanges welded on to fit 2016 Gem. Maybe he has pictures.
I would think that it will fit in any case as the 2003 mounts a different way.
Worse case saw them off. It is a classic Gem gearbox.