OK, unless someone tells me otherwise, here is my battery choice. 14.8V 4S, 2200mah. Not the most Amp hours, but it fits in the space in my chassis and I can always have a spare on charge.

https://www.wirelessmadness.com/over...attery-ol-2568

I would consider an Optipower with the FRA discount, but quite frankly I can't understand their website or find any products on it.