Solar overcharging?

[Tom Wootton]

I have a Unisolar panel rated at 1.96 amps and a combination cranking/deep cycle flooded battery rated at 110 Amp-Hours. I've read that no regulator is required if the panel is 2% or less than the AH capacity of the battery bank, but some sources put the percentage as low as 1/2%. I'm finding that I have to add water every week. A regulator costs about $70, and the one in West Marine has some LED's to monitor performance, charge state, etc. Does anyone have any experience with solar panel regulators? My other option would be to put the $70 toward an additional battery and parallel it with the existing battery, increasing the total AH capacity to the more conservative percentage. I see no need to seperate the batteries, since the outboard can be pull-started if the batteries are flat. Any thoughts?

 

[Miles]

Might want a regulator...

There is some disagreement about when you need a regulator. I've got the same panel (32 Watt right?) hooked to 2 4D batteries with no problems but after a string of bright sunny days on fully charged batteries the voltage can get up over 14.5 briefly. You might want to check your voltage with a voltmeter and see where it is. I'd guess you may very well be overcharging the battery, but only for a few hours each day. If the panel drives the voltage up to 16 or so you'll basically be equalizing the battery every day which isn't good. You can get a nice, cheap 3 stage solar regulator from Solar Electric Inc. (link below) for a lot less than West. Good Luck!

 

[Bryan C.]

You can find cheaper regulators

Competent authority I have read puts the unregulated amperage at .5%, the fact you are overcharging supports that.You can get cheaper regulators on the internet, for example, at the following URL they sell a 5 amp job for $28. No affiliation and have not used them, so use a credit card.https://www.internetservices.com/secure/solarelectricinc/

 

[Tim Schaaf]

Battery condition?

I would concur with the 1/2 percent. The fact that you are needing so much water is a sure sign that you are overcharging, and, as previously has been mentioned, there are cheaper regulators. BUT, remember that overcharging is a function of your battery capacity. Unless it has been well cared for, equalized, etc, and is not too old, your 110 amp hour battery may actually have much less capacity. In which case, it will overcharge much more easily. Why not put a low, known load on it for 24 hours, and check to see the discharge? If it does come down to spending seventy dollars, I would definitely go the two battery route.You could probably get away with a 1% charge rate, if you don't have to water too often.