Solar Boombox Upgrade

Ok so im looking to upgrade my DIY portable boombox for the 2nd time and one of the things i want to add is a solar panel to supplement the battery power from my 12v 7ah sla battery, that by itself will currently run the thing for about 3hrs at full blast. The new version will have Directed CSX-650 component speakers: (bottom of this page) http://www.lightav.com/car/directedaudio/directedspeakers.html and the amp will be one of these: http://shop.41hz.com/shop/item.asp?catid=42&itemid=43 , so what id like to know is what tech spec should i be looking for in a solar panel that would be capable of charging the battery while the boombox is not in use and will supplement the battery power to extend the run time while it is in use? Also will i need some kind of circuit/component to prevent overcharge of the battery?

Oh and is there some kind of simple light/gauge i can wire in to show the charge level of the battery?

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What sort of size are you looking for? If you want a commercial unit, you can get a panel with a battery charger designed for fitting to a boat or RV.

Alternatively, a panel outputting 12-14V will do. The minimum protection needed is a diode to prevent reverse current, as a small panel is unlikely to come close exceeding the maximum charging current of the battery.
ambientvoid (author)  The Skinnerz5 years ago
based on the size of the current version of the boombox i'll likely be aiming for a 10" x 18" panel or a couple of smaller panels depending whats available. I want it to be as easy as possible to link up with my limited electronics skills so i like the sound of the commercial units, though equally i want to strip as much weight as possible for this next upgrade so if the charger is particularly chunky/weighty i might have to opt for going with your second option...
That seems to be a sensible size to be useable, although I don't expect it is really worth the cost or effort, seeing as the extension in battery life is unlikely to be significant seeing if empties the whole battery in 3 hours. A better battery is probably a better investment.

If you really want to do it, you need to look for a panel or panels that can be hooked up in series to give the correct voltage.

Good luck with the upgrade.
ambientvoid (author)  The Skinnerz5 years ago
apologies my original post wasnt as clear as i intended, the 3hr battery life at full blast is on the current setup which is cheap 5.25" car speakers and a cheap and bulky car amp with pre-amp. the stuff i linked above are the replacement parts for this upgrade, and im told the battery should last closer to 7hrs with these more efficient parts.
Optimisticly, a panel that size will output 5-6Ah a day, and depending on the exact size and configuration will cost upward of £80, about 130$.

It actually looks as though it may work, based on some combination of these, although you may need some form of regulator depending on what the supply voltage comes out as.
ambientvoid (author) 5 years ago