View Full Version : Gel cell batteries...

06-15-2008, 09:59 PM
I may be able to get 12v gel cell batteries and was wondering if anyone uses these in their tractors? If so can I still use the original charger? I assume since they are a "sealed" battery there would be no boil over of electrolyte to mess up the battery box.

Don Thering
06-15-2008, 10:47 PM
Hello Steve; I know nothing about these batteries, but they would be very nice to have if they worked. The water level would not need to keep checking. I am guessing they would not take continual charging. But again it would be very handy to use. I'll be watching for an expert's word on this!! Have a great summer! Don fm. Mich.

06-15-2008, 10:53 PM
From what I've read, the AGM type batteries are not compatible with the original chargers. You'll have to get a trickle charger or some other charger if you want to use AGMs.

Maybe someone else would like to weigh in?

Nick :cool:

06-16-2008, 08:31 AM
Right on the money, Nick. Some basics...

Flooded batteries are tolerant of overcharging (up to a point). It causes venting and bubbling, which makes a bit of a mess and you have to add more water. That's why they can tolerate the original charger, which is basically a transformer, rectifier, and a timer (i.e. a so-called 'dumb' charger).

Gel-cell batteries have the electrolyte immobilized by adding silica gel to it. So they won't spill, but they cannot tolerate overcharge or high discharge currents too well, either. They require a special charge profile with lower voltages and currents than floodies or AGM's. If they are overcharged and vent, the silica dries out. You *can* pry open the vent caps and add distilled water to these to bring them back if they dry out (I've done it), but it is far easier (and better for the battery) to prevent it in the first place. Be careful, as some chargers lump AGM and gel batteries in the same boat and use the same profile. This is a recipe for battricide (again, this is first hand experience).

AGM batteries (also known as VRLA) use a smaller amount of electrolyte, and lock it up by having it adsobed by a fiberglass mat. It's still liquid, but won't spill. These batteries can handle higher currents (in both discharge and charge), but during charging, voltage must be held to about 2.45 volts per cell max. to ensure a long life. Since there is less electrolyte, any that is lost through venting during an overcharge has big consequences. And, if they lose any from venting, you can't put it back without physically dismantling the battery. Most 'smart' chargers handle AGM's well, tapering the current back as they approach max. voltage, and holding it there for a set time or switching back to a lower voltage.

A lot of people (and battery salesmen!) use the terms "gel cell" and "AGM" interchangeably, but there is a big difference. Verify the construction of the one you want to use by looking at the manufacturer's literature.

So if you use gel batteries, make sure you install a charger (or individual chargers) that specify they will work with gel cells, and that the batteries are rated to be able to deliver the current your tractor typically uses. For AGM's, a smart charger (or individual smart chargers) would also be the preferred choice.

Dave Brandt - expecting my E-15 'project tractor' to be delivered tomorrow!!!

06-16-2008, 11:53 AM
That's interesting Dave, thanks for the lesson. I had always been under the impression that AGM and gel cells were the same technology. :hmmmmmmm: Happy to know the difference now. Either way, I figured they wouldn't work with the original equipment.

Nick :cool:

06-16-2008, 07:07 PM
I figured there would be some issues. But if the batteries are big enough, not sure of size just yet, but they are the size of a car battery and deep cycle, it may be worth while to modify the charger, build, or buy one. The charger would have to be able to fast charge, then fininsh with a trickle charge then shut off automatically when the batteries reach the proper voltage so as not over charge. Another project......

06-17-2008, 02:36 PM
A (relatively) inexpensive approach would be to use 3 12V chargers with the appropriate smarts and attach each one to a separate 12V section of the battery pack. 12V chargers are relatively common, so that would keep the cost and complexity down somewhat.

I believe there is a discussion about doing this (with the original pack) elsewhere on this forum.