dumb question but i'll ask it, if i run twin 3s packs can i still get the same power and run time as a single 5s pack ? if so what size 3s packs would i need, only reason i ask is if i go over a 4s pack i need to get a new charger
You can run 6s i.e. 2 x 3s packs in series - 1515 2.5DF would be ok but you may want to look for a lower KV motor 1515/1.5Y 1500KV.
Ideally you would want to look for a set of Enerland 3s 5000mah packs (polyquest, flightpower, neu 25c/30c) - You can velcro /tape them together for 6s.
You could then use a parrallel adapter to charge them as a 3s 10000mah pack. I'm guess this will take a few hours on your charger.