Best GEM battery's

Now that I got your attention, :slight_smile: I wanted to share what I have found out. I’m very new to GEMS but very familiar With battery’s for 12v High powered stereo systems. Not sure if what I know in the 12v world transfers over but I just wanted to start a thread to share Ideas and info. Here go’s

I’m my world Gell and AGM battery’s work great BECAUSE they can be mounted in funky locations like up and under a seat or hard to get to places
Where checking a water level is next to impossible OR the battery’s need to be on their side ect.

GEMs are easy to service and check water levels. So flooded battery’s like the Trojan or Deka group 31 battery’s are a inexpensive solution compared to GELL or AGM. But if you don’t want to ever bother checking a water level the. Just go With the AGM or another maint free battery.

I have found no one that can either say that pound for pound the Gells or AGMs are BETTER then the flooded lead acid other then the fact that you don’t have to Maintance Gell’s or AGMs from what I have found is the extra money your paying for the Gell’s or AGM’s is for NOT having to deal with fluctuation of water levels.

That’s it for now hopefully we can get some more Ideas as far as battery’s go’s

BTW this is what I’m finding out as far as prices go.
This is for a set of 6 group 31 battery’s with at least 108 AH each

Trojan’s $1000-$1200
AGMs. $1200-1400
Gells. $1400-$1600

In Daniels list of alternative parts he lists a Napa branded Deka gell battery that’s a Factory GEM battery with a Napa label on it. Turns out all Napa battery’s are made by the company that makes Deka.

The Gell battery sells for $249.
The AGM battery sells for around the same
The Flooded lead acid sells for $179.

Interesting that the flooded lead acid had more cranking amps and Cold cranking amps then both the Gell and the AGM battery’s . So in short the flooded lead acid was cheeper and “on paper” a better more powerfull battery.

Here is some of the propaganda I was given

Napa AGM group 31
$249 800cc @ o degrees 1000ca @32 degrees

Napa lead flooded group 31
$170 1000cc@0 degrees 1200 ca @32 degrees

FWIW your charger figures in here as well. As you probably know, the charger needs to be reprogrammed if you change battery technology since the charging profile needs to match the type of battery in use. FLA are more tolerant of voltage overcharging than GEL or AGM. If you were using FLA and just switch to GEL or AGM without changing the charging profile on the charger, you’ll toast these batteries in short order.

Thanks for the Reply and yes Your correct the charger needs to Mach the charge profile of what ever battery you end up installing.
Stock Zigan chargers on older gems can be adjusted to charge AGM GELL and Flooded battery’s. I have even been told that Zigan can program to charge Lithium

I THINK the Zivans have to be sent to the factory to support Lithium batteries and I believe there’s an update that should be made to them as well regardless of battery technology.

My other observation is that not all batteries are created equal. I personally only use Deep Cycle batteries made for industrial applications. I once had a set of “Marine” batteries which lasted about 1 1/2 yrs before needing replacing. Cold Cranking Amps by itself isn’t a very good indication of the usability of batteries in this application in my opinion.

Cold Cranking Amps by itself isn’t a very good indication of the usability of batteries in this application in my opinion.

I’m glad you brought that Up that’s my next Question.

What’s a good indication "on paper " of a battery’s worth.

Cranking Amps, Cold Cranking Amps, Amp Hrs, Reserve?

In the quest to find a great battery what should one be looking for?

One thing is FOR SURE. Even the best battery’s won’t last if the are not charged correctly. So Mabey a charger needs to be part of the equation.
Do people have a battery and combination that they can recommend.

In my mind, the key to a good GEM battery in flooded lead acid (FLA) technology is simply “weight”. Heavier is better (more lead => more weight => more capacity) and of course “bigger is better” and unfortunately more expensive.

For me, Trojan deep cycle FLA batteries have worked very well. I’ll only use an “industrial” deep cycle battery since it’s designed for applications such as the GEM where the charge cycle is “overnight” and the discharge cycle is “all day” (e.g. floor sweepers, scissor lifts, tow motors, etc). I don’t have any experience with anything other than Trojans and Interstate Marine batteries so can’t comment on other brands.

The Interstate Marine batteries were in the car when I bought it used but weren’t up to the demands placed on them (IMO) and only lasted about 18 months from “new” before they started failing. I replaced one and then another failed shortly thereafter. Rather than nickel/dime the string, I elected to replace them with Trojans based on recommendations from other GEM owners and haven’t looked back. When I bought the Trojans I insisted they all had the same date code since I didn’t want to mix “old” batteries with “new” batteries.

I have a QuickCharge Corporation charger programmed for FLA which does an initial charge followed by a maintenance charge which seems to do well with my Trojans. I check water levels monthly and top off as necessary and manually cycle the charger every few weeks to force it into the deep charge, maintenance cycle over the winter.


AL thanks 4 your reply.

I agree with you FLA and other Battery’s have 1 thing in Common Weight.
More weight more Lead, that’s a good sign. But IMO only 1 part of the equation. I will take real life first hand opinions (like yours) more then what a piece of paper says. So thanks for the reply.

“Quick charge question”. I saw the thread about the R4F (ride for fun) quick charge or clone battery charger and the question came up about weather all the gems functions worked the same as if you bought the $100 more R4F charger. I was told that if you bought the Quick Charge you would loose or not have certain gem functions.

How was the install on your quick charger and how has it worked for you. If you have a link to where you bought it that would be great.
Thanks in advance

I didn’t do the install. I had the dealer in AZ from whom I purchased the unit upgrade the motor to the 7.5 HP R4F, upgrade the charger and reprogram the controller. The first two items went well but they really hosed up the reprogramming and I finally sent it to R4F. They reprogrammed it per my specs at no charge (it’s apparently built into the cost of their motors).

You can find the QuickCharge corporation on the internet. BTW, the charger “blew out” when my first Interstate battery failed catastrophically but they repaired it under warranty. Incidentally they also make an “octopus charger” with 6 separate 12v leads (one for each battery) as a special order item. That should help with the “balancing” of the charging for the 6 x 12v batteries. I’d probably use that unit if I were doing it all over again.


Sounds good. My I ask who did the work on your GEM. I have been talking with Daniel at Innovative Motorsport’s in AZ. He has fixed up over 1500 GEMs he Recommends the R4F charger. He says the R4F is more plug and play and then Quick Charge

Bought my GEM from Daniel who did the upgrades and QuickCharge private labels their charger for R4F.

Dustin at Innovation Motorsport is a nice guy and has been very forthcoming with advice and info about the GEMs He was the one that said that the R4F charger had worked with GEMs lock out Ignition feature (what ever that is) Bottom line it sounds like the R4F charger is more plug and play then the Quick Charge charger. But it sounds like if your wiling do do a little work or you know some tricks you can get the quick charge to work just fine.

I wanted to address balancing and the octopus charger that you tallied about. unless all your battery’s are separated or UN linked at charging a octopus charger or a charger with mutable charger leads is going to do you no good.

For a charger to address battery’s separately they need to be all un hooked From each other. So that would mean disconnecting the power cables from each battery so that they are NOT connected to one another and the charger can charge each one with out effecting the one it’s connected to

Well maybe but I’m still doubtful about the difference between the QC vs R4F chargers. The safety interlock simply keeps the GEM from powering up when it’s charging so you don’t drive away with it still plugged in. My QC has an interlock so I don’t think that’s the difference. I know R4F touts their unit pretty well but I haven’t seen any functional difference.

RE the octopus charger: I would THINK the onboard sensors on the charger in theory could “read” the difference between the plus leads between the various batteries and adjust their output accordingly to maximize the charge without overcharging each individual battery. But I haven’t researched it all all.

Ok that’s good to know about the ignition lock out. That’s the problem with linking multiable battery’s together is that your NOT able to see the difference in each battery till you break them apart. In the spirit of sharing information I will share what I know hopefully other can chime in to support my theory or denounce it :slight_smile:

Lets say you have 2 Battery’s separated Battery" A" is resting at 12.7 volts and Battery B is resting at at 12.0 volts its easy to tell the different voltages between the 2

The min you link the 2 battery’s together in a 12v configuration you will not be able to tell the difference in voltage. The weaker battery will draw down on the stronger battery and both battery’s will come up with a NEW lower combined voltage.

SO if you had a Octopus style charger that could address stronger and weaker battery’s and charge or Balance them accordingly it would ONLY work if they were separated.

I have several muti bank battery chargers for Boats and this is how they work. I use heave duty solenoids to link or JOIN battery’s while in use and then the solenoids break them apart for charging. Again this is in a 12 volt configuration but I would assume this would be the same in a 12,48 or 72 volt configuration,’’

And then here comes the problem once you break them apart your now charging 6 12 volt batters NOT one large 72 volt battery as the charger sees it

The problem I have with your “batteries in series” explanation is that my experience suggests otherwise. When I had a failed battery in my 72v string, I simply measured the voltage at each battery between the plus/minus terminals with a simple voltmeter. Admittedly I wasn’t “charging” the system at the time and the main breaker was off so there was no potential for current to flow.

Still, under these conditions it was very easy to tell the difference between the good batteries and the bad batteries. The four good batteries tested at around 12.7 to 12.8 volts, one bad battery tested at 11.8 volts and another at 12.1v.

Since the charger has 6 separate circuits, each attached to one and only one battery, I’d think the electronics would “read” their respective battery and adjust the voltage and duration as required to bring “that battery” up to the full charge threshold and after to hold it at a maintenance charge.

Incidentally if we were discussing batteries IN PARALLEL, I’d agree with your observations but GEM batteries are in series and I think that’s the difference.

Well if you were able to read the difference between each battery and see with a volt meter the lower Battery then I then there is no reason a charger couldn’t see it and charge it accordingly

I’m new to this and I was trying to apply what I know in 12v systems and 12v battery’s linked in series to apply in this application. And I know that to be the case 12v battery’s linked in series make a common voltage and you can’t tell the difference between each. I guess when you link 12v battery’s in parallel to make 72 volts that theory is out the window.

One other thing you might want to consider is using a BattSix on your battery pack. It works by having a separate lead from the meter to each battery. This allows the device to separately read the voltage of each battery in the string while you’re driving along and thus gives you a “State of Charge” (SOC) indication for each battery independently from all the other batteries. In theory it would allow you to see which battery is “weak” and potentially failing and/or needs attention.

The factory SOC indicator built into the GEM reads all the batteries as single 72v source. As the batteries are drawn down, the total voltage drops and the display is [somewhat] calibrated to give you an indicated SOC though I’m not 100% confident that I’d want to depend on that! And of course you can’t see the status of each battery individually.

I don’t presently own a BattSix myself so can’t vouch for it’s accuracy or usefulness but I’ve seen it mentioned often enough to warrant passing this along. If cost were no object, I’d probably get one just for the piece of mind it would provide.

battsix works very fine in my gem e2 and Gel battery

here you can see i have problem with one batteri

changed that bad battery and after some driving with my new battery

i can now see my other batteries are not perfect :wink:

Just curious about your battery replacement logic since you have the BattSix installed.

Do you replace just the identified “failing” battery? I’ve heard arguments both ways about replacing all the batteries at once or one at a time as they fail. I’m curious what your thoughts might be regarding this.

Incidentally I’d think you’d be a perfect candidate for the special order octopus charger from QuickCharge. Since GEL cells are much more finicky about their charging profile than FLA, the six separate charging circuits would charge up each cell only as much as needed with no overcharging needed to compensate for weaker batteries.