If you are using 9v, I use iPower brand batteries, been using them for a couple of years now, get about 8 hours per charge and they are good for 300 cycles.
They are expensive, when I started they were $13 ea, and the last time I bought some it was $20 I think...
For AA's I also use the iPowers, but there are several threads on here that discuss other brands that probably cost less and still give great run time...
Hope this helps...
Sean...
