Please define length of each use; ex, 10 min? 10 hours? this will define va rating you should shoot for...

Even my car radio/spkrs on my Electrak riding mower only pulls about 1.5 amps under normal volume level - until a really good song comes up on the 8 track - then maybe 5 amps max ;)

www.KilroyWasHere<dot>com

Well normal batt life should be around 6-8 hours. thats how long i would listen to it at work.

well if you use lithium based rechargables you will need a fancy charger that balances each cell (4 total) - complex so probably not worth it.

Or if you go for say a 14.4v rechargeable drill/charger I think you would be unhappy with the batt life - those typically use around 3-4ah (amp-hour) batts so I'd expect an hour or two max play time.

Lugging around a car battery seems too heavy but would give you probably 15 hours play time.

This is why large portable radios often use D cells; rechargable (NiMh) ones are now 10ah, so should give you 5-6 hours, then put them in a recharger or leave it on them in use (I do this with 2 way radios).

But the sweet spot for your scenario to me is one of the easily available 7ah or 9ah gell cell 12v units like this:

http://www.ebay.com/itm/Gell-Cell-12V-7AH-Battery-...

Available for about $ 12.00 each; standard wall wart chargers also available for them.

In case you don't know, bat are rated in ah; so you can simply take the total amps * the hours you want to run to see total ah draw. So your 8 hours * 1.5amp load means you want about 12 ah.... A smallish car batt is around 85ah for reference. Depenmding on your volume level, you may find your radio only pulls about 0.75amps for the level you want.....

www.KilroyWasHere<dot>com

decided to go with the sla battery. just what I got laying around. I did buy this charger http://www.ebay.com/itm/12V-4amp-Xtend-Tender-Char... with the radio a little less then half the charger is in the trickle mode powering it. "with out battery" after that it jumps to 14.6 volts. and with the cd playing at no volume it jumps to that voltage also. With mp3 i prob will never use the cd. But i should be able to charge it while it plays if need be. Thanks for you input.