Voltage regulator for solar charging

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C

Cal

Can those of you who have used a solar panel to charge their batteries give me some advice on whether I need a voltage regulator? I am using a Unisolar USF 11 panel (0.7A max) to charge a West Marine 73A/hr gell cell battery. Not having done this before I'm concerned that the panel will produce too high a voltage on the gell cell battery and over charge it. Has anyone had experience charging gell cell batteries with a panel? Thanks
 
M

Miles

General guideline...

Is you need a regulator if the output from the panel (in amps) is more than 1% of the AH capacity of the battery. Some people say .5% though and these figures are generally for flooded types not gel. Since you're at the 1% figure I'd say it would be a good idea but I'm not sure how the gel thing factors in. You can get a nice three stage regulator for around $30 from Solar Electric Inc. (link below), it's a lot cheaper than cooking your nice gel battery...
 
T

Tim Schaaf

solar gel cells

It is particularly important to regulate your panel, since you have a gel battery. Gel batteries are easily destroyed by even mild overcharging. When a wet cell is mildly overcharged, to some (but not the entire) extent, the damage can be minimized by monitoring water levels and adding water more frequently. You can't add anything to a gel cel, or other sealed battery, so they frequently come with a little extra electrolyte, to account for gassing. By the way, contrary to popular opinion, a gel cell does have pressure relief valves that can let some gas escape, a better outcome than a battery exploding! But, as this excess is used up, the equivalent of drying out a wet cell can occur, with no possible remedy. As a result, "sealed" batteries are VERY voltage dependent. And, you need to factor in ambient temperature to get the right voltage set point. Particularly if the batteries are in a hot part of the boat (engine compartment, for expample) their ambient temperature can get quite high at times. Most battery voltage specs are calculated using either 20 or 25 degrees Celcius, or 68 or 77 degrees Fahrenheit. Depending on your conditions, these can be relevant or irrelevant temperatures. Make sure to treat your gel cell very well, and with care! Or, you will be buying a new one......During the past couple of years, I have bought five different solar panels from Solar Electric Inc., and I completely agree that they are great, best I have found.
 
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