2002 Gem e825 will not go forward or backwards

Hello first post. I’m helping a friend who just got a 2002 Gem e825 With dead batteries.
I recommended the Mod 3 Tesla cells packs that are 24v and he purchased 3 of them.
I put them in series and installed them.

Here’s what works:
Lights horn

Here’s what’s noted:

  • 17v off the black fin dc/dc converter on the two aux wires that hang
  • 82v off each side of main battery disconnect
  • 82v through fuse and on other side of main contactor??(where the fuse is)
  • 82v Across the controller

When key is activated, 100 Battery? then 1009 milage?? Then goes blank.

Buzzer sounds when in road mode and not turf mode.

I hear relay click when turning key on

Gem does not go forward or Reverse

Parking break Plastic switch Arm moves when brake is applied and released.

Potentiometer pedal connector under dash is connected and in good shape.

When plugged in, zivan charger works
(I will reprogram for lithium or get him to purchase a new charger)

I have my meter, but I don’t know the pin out for potentiometer pedal and what pins to use for the Ohms reading.

My next thing is to clean the main battery disconnect lugs. The lugs under dash at fuse/contactor and on the controller as well as the motor.

Any addition fault finding techniques would be greatly appreciated.

I’m 22 years military with electronics back ground and have personally built my own electric propulsion vehicles.

Thank you!!!

Do you have a link to the batteries? 24v isn’t enough information. Nothing to do with your problem.
P13 needs to be low from parking brake.
17v is high for dc-dc. Are you sure.
Zivan has a relay interlock supplying the needed 12v from key.
Can I assume vehicle did not work previous?


I’ll double check the DC/DC converter but I’d be 100% that it was 17.2v yesterday measured at the two Aux wires from under the dash. However I used the purple positive and I used the controller ground as ground reference.
I’ll recheck going across the purple and the black that come Directly off the converter.

I do hear a relay click when turning the key on and off. I should see if it’s passing 12v to the battery charger.

The previous owner put brand new batteries in six months ago and then left the main battery disconnect on and killed the batteries. That was the last time it worked however, I know the previous owner and will confirm that it was actually working after the new batteries were installed. I believe he did it himself and may have connected them wrong (assuming he may have) killed the batteries. I’d like to think that’s not the case. He did say that it was dead due to battery disconnect was left on.

P13 ??? And needs to be low?
Exactly what does that mean and can you

Thank you

Email me for BASIC get you going guide from FSIP


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Pin 13 on the controller.
Converter should have a crow bar circuit preventing output going over 16 volts.

It’s alive!!!

Took apart all connection points at the controller/Fuse/Contactor and wire brushed all

It would appear that the schematic proved to be indispensable,

Probably more Than one failure point.

The emergency brake switch pretty well disintegrated when just trying to remove the spade connectors.

And possibly the ignition switch.

But the contactor finally made that big noise.

And she was moving both forward and reverse.

The minute I re-attached the relay switch and turned it back on the contactor started making connection and disconnecting making connection disconnecting making connection disconnecting so I removed the relay from the firewall again and all of a sudden it worked fine.

I bypassed the emergency brake brake switch by connecting the green/white wire with the white wire and left the yellow wire open.

Took it for a ride and it does 29 miles an hour and the wheels spin easily even from 20 miles an hour and smash the potentiometer down and the wheel spin again LOL Must be because there are light lithium under the seat and nothing up front any longer.

I need a charger that will do 88.2 V for this lithium set up.

Any recommendations that will work with this 2002 GEM E825?

I hear that I might be able to change the profile in the Zivan.

I so appreciate your help “Rodney” as that schematic diagram allowed me to go through the entire vehicle to make sure that everything was operating as it should be.

After cleaning all the connections, I rechecked the DC/DC converter and it was 13.3v. :blush:

Run the VIN thru NHTSA.gov and check for recalls. There are ones For your model on the DC/DC converter as well as on the parking brake assembling that if not cleared, Polaris will fix under warranty.

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I wouldn’t bother chasing that dragon. I’ve been to the sole US distributor’s shop and talked to them. The charge profiles are on an eeprom, it’s not something the user can flash. I had a zivan which only did FLA and AGM that I wanted some profiles (like gel for example) added to, they said no dice. It seems you’re kind of stuck with what you got on the label on the front for where to set the dial. The one thing they can do is go up or down on the amperage.

My 2-yen, talk to @LithiumGods or @Inwo about a modern charger that has the right profile for your batteries and relocate it from under the dash to somewhere it fits properly.

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Does anyone know the max voltage the controller can take???

You probably have the T2, which is 95 or 96 volts. When you go above that you’ll get a -77 error and it won’t run.

Oh that’s awesome… my buddy’s lithium packs are 29.4v each hot off the charger
For a total of 88.2v

I’m looking for a 21s lithium charger
Tesla Model 3 cells in a 40p 7s pack configuration each with breaker and BMS.

3 of theses packs in series.

Test drove last night. 29mph on the dash

Looking for a good charging solution…
Delta QuiQ 1000 72v is on my mind for him.


Yes, DQ is best bet.
#163 = 85.5
#53 = 87.6
#123 = 89.1

I would not charge until bms cutoff, 4.2v often.
Gem probably will not start when over about 86 volts, nor run when over 95v.
I’m sure @LithiumGods has some dq in stock. I’m about out except for some DCI in a warehouse.

Looks like you made a good choice.
21s is perfect for early Gems.
Let me know if bms ever trips. I may run harder than you, but I trip 300 amp bms.
I’ve been reluctant to sell batteries with 300a trip.
From your specs.
Power (Amp): 100A Continuous, 200A Peak

Tell us about your bms setup

He posted a link. These are neat drop-in batteries that someone put together with small 2kw Tesla modules.
How they get 3 bms to work together, I have no idea. Bluetooth maybe?


I haven’t tripped the BMS on test runs stomping on it.