Cell count needs to be the same size (capacity in mah) does not matter

Packs need to be at the same state of discharge (voltage) when you connect them

You need a parallel charge lead for the main lead on your batteries and also a parallel balance lead (or paraboard charging board)

Get the leads / boards from here

http://www.progressiverc.com/adapter...arallel-cables

http://www.progressiverc.com/adapter...-charge-boards


Cheers