GEM charging issues

I recently bought a 2002 GEM E4, in stock condition with a Zivan charger and older looking gel batteries.
The car runs and drives, but no matter what i try, I cannot get the charger to kick on.
I have checked the internal fuse, all connections, cleaned all battery leads, but it will not come on.
I have charged the batteries individually , and drove the car back down to 40% charge.
I tested the batteries, (Discover AGM )they are fair, all about 12.3 volts, 10.8 under load test,
I was thinking, there must be a hidden fuse , or a connection i am not aware of.
I understand the charger does not activate unless the batteries have some power, but they should come on at 40% to 70% ??

I also found what i think is the heat sensor, a black lead off charger with a round end , just hanging in the front battery conpartment, may be an issue? not sure where it goes…

Any advice would be greatly appreciated.

Boxboy, did you get your Zivan charger working? The Zivan is powered by a cable that goes under the floor and up to the charge plug under the seat. The end at the Zivan charger may have a plug on it that could have come out partially. If it has the plug on the cable, it’s the same as a computer which means you can try a regular computer power cord to see if that’s your problem.

It’s not a good idea to wait till the batteries get discharged that far before recharging. I suggest you use your 12 volt charger (or multiple 12 volt chargers) to recharge after each use rather than waiting so long. Lack of prompt recharging is the number 1 reason the battery life is reduced. Golf courses charge them every time a cart is returned to the lot, even if only used for 1 round of golf. Batteries are the single biggest factor in your cost per mile. If you get 5 years out of them but only do 1000 miles, that’s over 1000 dollars for only 1000 miles or $1 per mile. You need to really drive the heck out of these to make battery life less of an issue. 10,000 miles in 5 years is still 10 cents a mile at $1000 for a set of batteries (which is considered cheap).

Bob in MA - 2002 GEM eL (XD?)

Hi Bob

Many thanks for those very useful tips, when you look at the information you have listed it all makes sense. Battery life is key to the future of the EV market and any savings or efficiences we can make there will mean better value for money.

Do you have any other general tips for getting the most out of your electric vehicle?

Use it a lot I guess and keep the SOC above 50% at all times. I would like to see a balancing charger which doesn’t overcharge to balance like the Zivan does. 6 batteries need 6 chargers in my opinion like my LiPo packs for model helicopters. They have a balance connector which charges each cell separately to make sure all cells receive the same charge level. Series cells within a battery are probably OK since they were all made at the same time using the same materials but 6 individual lead-acid batteries can develop imbalances over time. That’s why the chargers do a certain amount of over-charging to get the low cells up to full charge (at the expense of the others).

All the battery charging tips are in the owner’s manuals but how many actually read them? These forums are a great resource but you have to read all the posts to glean those gems of information that are available.

Bob in MA

Hi Bob

Some great comments there - how do you feel about battery swapping stations which seem to be an interesting topic of late?


If the vehicle is made for this purpose and the batteries are standardized I can see it working. It only makes sense if all electric vehicles use the same battery pack and they’re all designed for quick changeout.

There would have to be some sort of contract relationship with the battery station to protect the car owner from receiving a bad pack and getting shafted for it. I’d certainly hate to show up 30 miles into a 100 mile pack and have them tell me they can’t swap mine because it was “bad”.

The infrastructure for the quick-change battery station could easily be accommodated by using a service bay (remember when gas stations had those?) with a special fixture to swap out the heavy battery packs and a charging area for the removed packs. The charger would be expensive as would the handling equipment so I would expect quick-change batteries to cost about the same per mile as gas-powered fill-ups do now.

The only advantage would be the ease of extended distance travel compared to the typical overnight charge you’d need normally. A car that uses $5 to $10 of electricity to charge at home might cost you $30 - $50 or more to quick-swap due to the labor and equipment costs.

But that’s just my opinion - who know what will really happen?

Bob in MA - 2002 GEM eL (XD?), 2012 Prius V

Maybe they could be a short term fix while the worldwide network of electric car charging points is expanded?

QuickCharge Corp has a balance charge adaptor for exactly this purpose. I’ve been thinking about getting one and installing it on my GEM.


The problem with QuickCharge’s shunt regulator is that it’s totally dependent on proper charge profile being known so it can be calibrated. If the charger puts out more than all 6 batteries need, yet senses the high load from the shunt regulator; you’ll have thermal runaway on the shunt regulator. It’s a delicate balance and, in my opinion, not really a great idea for the GEM. Besides, where would you mount it? It either has to be mounted to a metal surface or hung in open-air for proper cooling. There’s not enough heat sink available on the GEM to mount it to a metal plate unless you added one under the seat. Bare metal plate on top of several deep-cycle batteries - right… Not a good idea IMHO.

What would work best would be 6 separate 4-stage 12-volt, 10-12 amp chargers; each connected to its own battery.

Some Really Good Info … Thanks to all

The mounting position stumps me as well and has kept me from exploring this idea. There isn’t much left room anywhere except under the aluminum bed on my short bed E825.

As far as charging profile is concerned, since I already use the QuickCharge OB7210 charger, I’d THINK that they’d be a able to calibrate their regulator pretty closely. Haven’t talked to them about it however. May call them next week to ask and report back.

By the way, another suggestion I’ve heard to extend battery life is to pull the batteries out and shift their relative positions every year to even out the effects of charging the batteries in series. Though given the aggravation factor involved w/ pulling batteries, I’m not sure how practical that is.

Given the cost of a set of new batteries, I’d like to maximize the life of the ones I just bought.


Swapping them around won’t accomplish anything except give you a hernia. Moving one battery to a different part of a series string still does nothing to change the current path. It just re-orders it - but that doesn’t correct an imbalance. Series batteries will always develop an imbalance after several charge-cycles unless a balance charge is done. On flooded-cells this balance charge is done through timed over-charging which, on flooded cells, just boils off some water which you then replenish as part of regular maintenance.

On gel or AGM batteries if you overcharge them, you shorten their life dramatically. The shunt-type balancer is one method of dealing with series-charged batteries to prevent the over-charge from occurring. Another way is to do per-battery charging instead of series charging. This requires a more expensive and complicated charging system with many more wires than the standard charger.

In my opinion, if using flooded cells, just accept that you’ll be adding water occasionally as the charger purposely overcharges some batteries to assure they’re all fully charged.

Now, on the other end of the spectrum, there’s LiFePO batteries which ABSOLUTELY REQUIRE accurate and safe charging voltage cutoffs. These usually are installed with per-cell regulators which bypass the cell once its peak charge voltage is reached. These onboard battery management systems are a necessity to prevent dangerous puffing, swelling or severe fire and explosion hazard. I would only go with the battery manufacturer’s BMS system though. It would be difficult for third-party manufacturers to make many different models for specific brands/styles/chemistry in the different cell types.

The original logic I believe was that the first and last battery in a series are typically working harder than the other batteries and moving them around gives all of them chance to do the heavy lifting which equals out over time and therefore extends the battery life of the entire string. Of course I don’t know if this is correct or just urban myth.

Anyway thanks for the information.

No, they all work the same in a series string. I think you’re confusing a parallel string like found in a trailer or RV where you need 12 volts but lots of amp-hours. The positive cable goes to one end of the buss carrying all the positive terminals and the negative cable goes to the other end of the buss carrying all the negative battery terminals. Due to the slight resistance in the buss cables, there’s a small voltage drop along its length. Feeding all the positives out one end and negatives out the other end more-or-less equalizes the voltage drops and evens out the discharge across all the parallel-connected batteries. If all cables are equal size and length there’s no need to move batteries around during their lifetime.

If, however, due to physical constraints there’s unequal length cables along the buss the one with the longest cable run will get less use than the others. In that scenario, you’d swap them around yearly.

As I said - there’s no need in a series string. I are a enguneer. I studdied dis stuff in skool.

Thanks! I learned something today AND saved a lot of straining and grunting next spring pulling batteries out for no good reason. <VBG>