GRJ.....If you can get a NiMh in give it a try.Consider "forming" your cells by charging at low (1/10 C) and discharging at the same rate about 3 or so times. Without this most chargers will indicate fully charged at a partial charge. Don't fast (1.0C) this chemistry cell. https://www.rcuniverse.com/for...arge-nimh-packs.html
Don.....Sorry if you felt offended about my post. I did include your cell type as a safer option. I see that you are controlling charge/discharge in your packs. I concur that is a good option for plug and play use on this application. I've been at this a long time also. I've also used Li ion packs in 25 lb gas powered models. (radio/servos only)
I bought this battery and charger on Amazon, pretty cheap to tinker with. The charger says 400MA output. I can easily use my bench power supply in constant current mode to taper charge at any current I like. It appears it just fits into the tender side to side, I'll just have to replace the speaker with a lower profile one. I have at least a hundred speakers, I think I can find one...
I'm not ready to spend hundreds of dollars getting started just yet. This may end up being a flash-in-the-pan for me, you never know.