483 watt 36 amp Gel Cell Control System

[iFred]

I have found that Gel Cells last longer and produce more power for longer if care is taken in the control of the power applied to them during charging. A nice slow charge is better then a fast charge. In general, sealed gel cells are great. Sealed Gel Cells require however a very stable power system capable of maintaining the power at 13.8 vdc with current protection. Unlike car and acid batteries that can take overcharging and just boil off the extra current but require refilling and maintenance. The need to produce a controller that could handle this and be upgradeable as I increase my system was also an issue. So after a couple of weeks of thinking about it I found a solution to the problem. At this time I have 9 sealed gel cells at 24 ah each hooked in parallel and intend to hook some more up soon. The generator is now putting out really nice, I got 600 watts this week in some high winds, which ain't bad for this application, almost to much power.

This a special power system that I just finished building, it is a 483 watt 36 amp 13.8 vdc Sealed Gel Cell battery charger for my windmill. Composed of  24  1.5 amp 5 volt regulators (on the top 2 aluminum frames),  a variable 1.2 to 35 vdc regulator booster for the 5vdc regulator adjustment (7-19 vdc controlled output) and a shunt diverter using 741 op amps for detecting and trigger and 3-75amp 55 vdc mosfet drivers for the load matched with a  hysteresis control system (load matching).  The diode board is for preventing battery feedback. I can now control the exact speed at which the generator spins and produces power at an exact amount. So it's now up and running and I am testing it, sorry no schematics at this time.

[RobD]

Hi Fred,
I like gel cells too but I don't use them in my solar applications here's why:

Gel cells are finicky about charging, they like a two step charge. Usually they charge to 14.7 volts for a 12 volt cell at C/10. (C=amp hour capacity of the battery) Once they reach that charge the charger drops off to the float voltage, about 14.1, and remains there.

Because they have problems with gas escaping through the one way valve and the battery drying out if over charged they can't get the full benefit of a high current charge from the windmill without damage. Also several in parallel means that some batteries won't get the right charge or worse be over charged waiting for the 'slower' batteries to 'catch up'.

You might want to look into sealed AGM batteries from Concorde or MK. They don't have the charge restrictions of gel cells but they do have the high recycle ability that standard lead/acid batteries have.

If you look at commercial applications of gel cells like in UPS systems you'll see most of them use only one battery that sits in standby with a trickle charge on in most of the time. This is an ideal application for gel cells.

RobD

[RobC]

Good work Fred. I was looking through the facts section and it states regulators aren't nessesary that batterys will bring the voltage down to their level. They sure will and if your generater can't handle the increased amp load it will burn up. Not to mention that I have some high dollar sealed lead acid batterys that also need carefull regulation.  Looking forward to a schematic. What did it cost? RobC

[iFred]

Thanks for the thumbs up! I looked at one of the professional chargers for these batteries and ran some tests on it, it was exactly 13.8 vdc. The current did change from about 5 amps down to trickle charge at 400ma. but the voltage stayed pretty constant. I got all the batts for free from a local golf cart dealer friend of mine, if the bats do not hold up to the 18th hole then they are discarded. I and a freind of mine ran tests on all the batts with a 2 ohm load tester and the batts appear to be in really good shape. I figure somewhere between 15-18 amphour per batt so I can't complain and I get fresh batts every month or so.. The recycling method is paying off and I can't complain about free power LOL..