Grip on solar panel help?

[the_shazz]

So i'm building a solar recharging boombox (after building a solar recharging cooler/boombox) and decided to up the power by using a 5W solar panel instead of the 1.5 i used before, and a 12v 5ah battery instead of 8 AA's.

My problem is this:

i bought the Grip on 5W solar panel (Sku 365-102), and it says that it prevents overcharging of the battery. I'm curious if it actually actively prevents this, or the current is so low that it's not possible (i've emailed the company with no response).

Also, is there a diode in the assembly somewhere? I feel like all these trickle chargers do, but i'm not sure. This thing is so bare bones, i dont know where it would be.

Thanks for any help/knowledge

[JimHRB]

Not familiar with that particular unit, but here's some general info. A 5 watt panel only puts out about 1/3 amp and that's what prevents the overcharging. However that's based on an auto sized battery and you are using a much smaller one. Key is the difference between what the battery can accept and the panel put out. At higher rates of charge, a charge controller is needed. And no, it isn't built into the panel. Most panels come with a diode to prevent discharge when ther's no sun, but you'll have to confirm that for your unit.

[the_shazz]

I'm going to be using it with a 12v, at least 5Ah sla battery. hopefully thats not small enough to be dangerous. I guess ill just throw a diode in there to be safe

[Ryan_M]

Lead-Acid batteries are easy to build a charging circuit for. Basically all you need is a constant voltage source. Look at the manufacturer data sheets to see what voltage they like, usually ranges from 13.8V to 14.4V. Though to be honest I don't think it's really critical... sure you may not be charging 'optimally' but LA batteries are damn near free at surplus shops in the event you take a bit off it's life span. But there is no danger either way if you're in that range.

See what you need for voltage and see what that solar panel kick out in direct sunlight, if the voltage is as above then no extra parts required (which maybe what they mean by preventing over charging). If that's the case then just hook it straight up.

BTW no harm in paralleling smaller batteries if you find a good deal on smaller ones vs. one larger one. You just add the Ah.