Acceptable battery variances (voltage)

I have a set of battery’s that are less then 3 months old and I have found one of my battery’s that has a lower voltage and I was wondering if it would be enough of a voltage difference that I should return/replace the lower voltage battery.

Here is how things lay out
Battery#1 12.86
[B]Battery #2 12.65[/B]
Battery#3 12.85
Battery#4 12.87
Battery#6 12.86

So you can see Battey #2 is the lowest in my pack.
It was brought to my attention via the octopus charger would show all 5 battery’s fully charged and the #2 battery would have a yellow (not fully charged indicator )

After three months, they should be broken in by now. Try switching the #2 with any other battery and see if the problem follows the battery. If it does, I believe you should warranty that #2 battery. I am beginning to like the idea of parallel chargers.


Well the other day I returned to find the charger had fully charged and equalized all battery’s. They were all in the 12.86 range. I guess the charger just needed some extra time to work on that #2 battery

It is interesting that you discovered the problem w/ your new charger. I’m certain a BattSix indicator would have discovered and displayed the same phenomenon. Furthermore I suspect you would have found the same behavior occurring (and being corrected via “overcharging” the string) using a standard 72v charger if you’d checked under those conditions.

I am certain that [U]any[/U] batteries in series will have this type of behavior occurring since not all batteries are equal, even from the same OEM and mfg date, but as owners we’re simply not aware of it because we don’t check regularly or don’t have the technology to do so as you now do.

One of the big reasons I favor FLA over other battery technology is that the entire string CAN tolerate being “overcharged” in order to equalize one “weak” battery of the string.

The very best approach of course is to do what you’ve done and install an octopus charger which will charge each battery individually as needed without consideration for the other batteries in the string [B]and[/B] presumably could be programmed for the charging profile for other battery technologies besides FLA (i.e. GEL, AGM). It would have been ideal if GEM had designed the original charging system this way but of course the cost of the charger would have been higher and that would have raised the cost or driven down the profits!

Thanks for posting your experience with this concept. It is very helpful to others I’m sure.


AR it’s you that got me thinking in the direction of the Multi Bank charger so
thank you.

Because the Multi Bank charger is made up of 6 individual chargers they each can be changed via flipping a few dip switches to charge all of the different charge profiles AGM GELL ect. I don’t know how this could ever work for us GEM users but it’s possible.

I agree the Batt Six module would do the same thing (identify the bad or week battery) but then you are still tasked with fixing the bad battery.
and for $500 its a great tool

but for a few hundred dollars more. (I think I payed $675) buy the time i got the Lock out and the Remote Led’s you now have a Tool that can identify bad or week batts and it will fix them as well. I would still like to have the Batt Six module in the future but thats down the road

I certainly agree that the charger you bought makes a [U]lot [/U]of sense. I’m only unhappy that I discovered the product [B]AFTER[/B] I replaced my OEM charger with a different QuickCharge product.

It was interesting to me to see the effort required to retrofit your charger and the results you’ve obtained. Thank you for posting all that. If I were ever required to replace my onboard charger again, I’d go with the charger you’ve got.


AR; The quick charge multibank charger I installed is not for the squeamish. The charger measures 22 inches in length you will find the back firewall of your gym with all its Electronics removed is around 23 1/4 inches long leaving only a quarter of an inch or so . Having to make a new firewall and relocate all the stock electronics would turn most people off. I could see any Gem mechanic That wanted to attempt this charging you $5-$700 minimum to do this.