Suitable battery for a supersmall/light boombox?

[saabaab]

I use a LiFePO4 12v7ah Battery with great results. It charges in a few hours max with a schumacher battery tender, about $25, and a charge lasts for a day or two. The Boombox weighs six pounds and gets extremely loud with a TPA3116D2 amp. The Boombox can play and charge on the fly with a standard dc power port. You can also charge it from your car and with an adapter, use the Boombox's power port to charge your phone, tablet, etc. I have a 10amp fuse on the line between the power port and the battery, just in case. The box has been extremely reliable for a year or so now. No issues
Another option is to use a drill driver battery pack from sears. Cheap, powerful, safe. The advantage is that you can easily swap batteries when one runs down. The disadvantage is that you can't charge on the fly.

 

[dangus]

Probably not very dangerous... There's zillions of cheap Chinese things out there with lithium batteries, and hardly any of them actually explode. The ampere-hour rating may be fictional, and the cells could be recycled from discarded laptop batteries. I know that when I opened up a cheap bicycle light battery pack, the cells showed signs of previous spot-welds.

I'd be inclined to salvage 18650 cells from discarded laptop or tool battery packs myself, test them for capacity, and fit them with a suitable PCM (protection circuit module). 3 cells in series gives a nominal 10.8 volts, which is a bit low for amps that are optimized for 12V lead-acid battery supplies. 4 cells in series exceeds the maximum voltage rating of TA2024 chip amps, but interestingly Yamaha's YDA148 class-D amp is rated for that voltage range.