I use On-Time Elite slingers on my deer feeder. They use 10 AA batteries. Battery life is good, but I would like better. My question- how can I charge 10 AA batteries (15 volts)? I know you can buy 6v and 12v chargers, but not 15v. Any advice?

you can buy solar pannels that have 15 to 20 volts with a regulator built in... or you can get a solar pannel with 20volts with a sun solar regulator to regulate it where you need it.

Your feeder will run fine on 12 volt battery. They typically hang around 13.5 volts and with the solar charger attached are around 15 volts. Just get a 12 volt rechargable battery and solar cell.

What batteries are you using now?
Look and see what kind of battery your manual call for.
Rechargeable Nickel cadmium batteries are 1.2v X 10= 12v
Non rechargeable Alkaline batteries are 1.5v x 10 = 15v
Some electronic are voltage sensitive and may not work or be damaged by + or - on voltage. OEM will specify type battery to use.
If it uses 10 x 1.2v NC rechargeable just add an external 12v solar panel and power jack and wire up.



Or for heavy duty use:
If it is 12v system get a 12v, 2 to 4 amp hr rating Lead acid sealed gel battery and mount external. Add a 12v solar panel and wire in power jack
http://www.radioshack.com/product/index.jsp?productId=2102489

Protect all wiring from coons with armor flex and j boxes