Electrical Gremlin, posi traction 0n 2002 gem?

GEM Forum
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Good day ladies and gents. I have a few questions i am sure are super basic to most but i am totally new the GEM cars so please pardon my ignorance here. I have a few concerns with a 2002 gem E825 4 seater I took off my buddies hands for my daughter and I to mess around with.

#1 is if the cart is up on jack stands, should both front wheels be spinning at the same rate when you apply the pedal to the metal..i mean plastic or fiberglass whatever this thing is made out of lol. I was testing the load on the batteries (another issue i will address) at 5MPH when i noticed my pass side wheel acts like it wants to spin but doesn’t. It is free of the brake as i can spin it freely by hand. I just installed a set of disc brakes up front so there is a tiny bit of drag but i can push the wheel with one finger. The driver side is doing all the work. Is this the norm or do i have a problem and if so what is the remedy or test for the remedy?

#2 As mentioned in #1 i have some sort of electrical gremlin. I can charge the batteries to a complete charge (Quick Charge SC07210 charger date coded JUN-20) and take the cart out and run it down to lets say 80%. When i stop and turn the cart off and then immediately turn it back on again the charge says 40% and i go into a crawl mode if the cart moves at all. All the batteries are from 2024 and all individually read 13.1-13.3 on what the quick charge is sayin is a full charge. The load test i performed was simply done with a voltmeter on each battery with the cart running at 5MPH. There is some sort of huge quick discharge going on and I am not familiar with the intricacies of the electrical systems on these yet but would love to learn how they work so I can keep my daughter on the road safely ! Any ideas what could be causing this discharge? Also the little indicator light above my dash is cut/disconnected i guess due to the addition of the quick charge charger which has its own indicator built in? I would love to reconnect that if its possible with the aftermarket charger? Thoughts on the issue?
#3 My buddy gave me these parts to add on accessories like light bar, sound bar, portable Android, etc. I plan on using a relay between the key switch and the converter and then converter to the control switch box with its own fuses. Can someone explain where i would take the 72V feed from into the converter or would the converter already present on the cart (stock) be all i need to run into the switch panel and power all the 12V stuff? Here is what he gave me…

step down converter
step down converter1868Ă—4000 382 KB

controller
controller1920Ă—897 113 KB

fuse block
fuse block1868Ă—4000 448 KB

fuse
fuse1920Ă—897 183 KB

Any help on any issue would be greatly appreciated guys. If this is to many questions in one post i will separate them out just let me know fellas.

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#1 is normal

#2 could be a bad battery OR could be that one of the boards in your quickcharger has gone bad. I had to replace 5of6 on my 2018. You can call the company and they can help you figure it out.

#3 you would direct wire to the battery. You will have to figure out how to tie the little red wire for the bus bar into the ignition or direct wire that to the battery as well. Then you wire your accessories into the bus bar.

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#3: The thing that says 60A on it is a circuit breaker of sorts. They work great. I use one on my parade float to connect my add on DC/DC converter. One thing about a relay is that it is not so easy to find a relay that is rated to switch 72vdc unless you go to a pretty good size one. Some converters, not sure about that one in the picture, have a place to add a switch to turn them on/off without having to switch much current. (they have something like a MOSFET to do the switching).
There is a good chance your existing DC/DC converter in the car will supply enough to run accessories without having to add that other one. Just depends on your accessories.

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#1 - Wheels different speeds - This is a normal activity of the differential build into the gearbox of the Gem. Without it, you would scrub the tires in corners. The tire spinning faster when both wheels are up off the ground has less drag on it. Try slowing it down with your shoe or a board and the power will transfer to the other wheel.
Since this is a learning vehicle, I submit the following visual reference.

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#2 Electrical Gremlin?

Be aware that the display is only a voltage based device and not considered very accurate. It guesses the SOC (state of charge) based on V. I’m not sure how often it updates when driving, but it checks at KeyON.

You should expand on how you are doing a pack checkup a bit more. The voltages you are reporting have a LOT to do with WHEN you are taking them. A full charge reading is going to be very different when “hot off a charge” cycle, and a couple hours after a cool down Resting period.

All the batteries are from 2024 and all individually read 13.1-13.3

This is good, but see if you can get the Voltages a bit closer to each other. Use an external battery charger and boost up the low ones. This is called balancing. You pack is only as good as your weakest battery. When using, they should all travel up and down at the same rate.

Your load test using a voltmeter is valid except you should probably run faster, possibly even full speed. You can also do this in the driveway without going anywhere, by holding the brake with one foot and applying the throttle at the same time. Try to be consistent between batteries to get a good read on all 6 what is happening under the same load conditions. Note the low, but also how high it comes back up when load is removed. You are looking for a large drop and one or more that is different than the others.

All the batteries are from 2024

That is a vague description. There is a big difference between Jan24 and Dec24. Even if they are 12/24, they are now 6 mos old. A pack can be fatally damaged in 2 mos if abused.

You did not say what these batteries are. All batteries are not created equal. If wrong type, undersized, not cart rated, not balanced, ignored over winter break, or not maintained properly, they could be not up to the task of cart demands.

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#3 - 12v Accessories
You have the right idea by using a DC Converter. You are free to add another one and a totally separate 12v system to power other accessories.
You should also identify if your car has had the DC Converter/wiring update installed. If yes, the converter in the car is good for about 30a, so an additional converter may not even be necessary.

@SDGem quote →
#3 you would direct wire to the battery.

NO! Stop!
You should never tap direct off a battery as a lazy way to power a 12v device (See Explanation #2 above). Doing this has a high potential to create an imbalance in your pack that will eventually send it to a cascade failure.

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I always wondered how the differential worked.. that old video was very helpful actually..

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You can almost hear the clatter of the 16mm film projector.

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