Battery overcharge ?

[GunnersHusband]

Here's my question. a 12v battery..... on a constant 2-3amp 10watt charge..... will that over charge the battery if left on for an undefined period of time? I would think that the low amperage would be able to match the amount that the battery discharges while sitting. most trickle chargers for RV's seem to run about that rate. Any opinions from those that know better would be appreciated. I'm a wrench turner by trade, I'm barely able to splice wires let alone figure out complex electrical equations.

in case anyone's curious why I ask. I have an old solar panel that I'd like to hook up to charge batteries, it has a diode to prevent discharging the battery and of course would only be charging during the day but it would be left connected all the time with no fancy charging control etc.
Thanks

 

[CCATLETT1984]

2-3amp is a bit high
i would get a "maintainer", they will cycle on and off as needed.

 

[GunnersHusband]

I suppose using what you've got to save money only really applies when you're talking about a little bit more than $20

 

[cranetruck]

The maintenance charging routine is explained here:
http://www.chargetek.com/3state.html

 

[Bill W]

I'm confused ( but thats another story) if you have a 12v, 10watt charger then it should only be putting out .83amps ( watts divide by volts = amps )., how did you come up with 2-3amps

 

[GunnersHusband]

I put a multi-meter on it and it's just a solar panel, not technically a charger. according to the label it's rated for 12-17vdc and 10watts. I'll do some more digging when I get back home monday.

 

[Jake0147]

It's a dumb device. It just pumps out electrons. The more the draw from the load, the more it drags the voltage down. The less the draw, the more the voltage raises.

Battery voltage raises with state of charge. It'll draw more and more (up to what the panel can produce) when the voltage is very low, but as it gets up to twelve volts, the charge rate will twindle, but be persistantly charging right up until 17ish volts. (You'll find that this varies with many factors). So if your discharge rate is fast enough, that'll help for sure. if your discharge rate is not fast enough (and if the batteries are good, it shouldn't be), then the solar panal will eventually (over a long timeframe...) cook the otherwise good batteries.

A bird in the hand is worth something, but unless you're making daily voltage checks, I'd suck up and find a smart charger/float charger, something that knows to stop charging at a certain point.

 

[CCATLETT1984]

http://www.elecfree.com/circuit/power-supply/lm2575-switching-regulator-12-12v-for-solar/

that circuit could be used, hook the solar panel to the input side and the battery to the output side.

 

[GunnersHusband]

wow guys, that's terrific, thank you for the info.

 

[cranetruck]

For proper battery charging, you need to control voltage and current and monitor the battery as well. Here is a typical charger controller IC...
A 50 Watt solar panel would be ideal here to restore charge and trickle charge the battery.