The other thing you have to take into account is that once you get over 5000mah - 5500mah range you are no longer running a series pack but a combo series & parallel pack. You can distinguish between the two as a 3 cell series pack like the 5000mah will have a designation on it like 3S1P. This means there are 3 cell running in series and 1 in parallel or in other words 3 single cells running in series each having their own balance line on the port. You can tell once you get into the parallel packs because they will have a designation like 3S2P. This mean you have a total of 3 cells running in series and each one of those cells has an additional identical cell wired in parallel for a total of 6 cells in the battery but again you only have 3 balancing lines on your balancing port so each pair of batteries relies on a single balancing port to balance them. Some people say that those types of packs don't always balance every cell perfectly because instead of balancing 3 5000mah cells the pack going to be trying to balance 6 3800mah cells on the same 3 balancing leads. They're basically taking 6 lower mah cells and wiring them up 3 in series to get you to 11.1V and 3 in parallel which which double the mah value. The problem is that while in theory this should work fine (and even in reality it typically works fine from what I've heard) there is a chance that not all the cells will be balanced as well as they could if each cell had been individually balanced. Your charger is only gonna see 3 cells not 6.
The other thing to consider about these packs is they are gonna have bigger dimensions than a standard series pack so if you have limited battery tray space then this could present a problem. An example I pulled off a pair of gensacearespammers 2 cell batteries, one 5000mah which is 25mm thick and a 2 cell 10000mah pack which is 48mm thick. Just 2mm shy of being twice as thick. This makes sense considering the pack has twice the mah.
IDK, this is just something I've read here and there. I know people who run packs like that and never have any problems and I know a lot of guys that wont have anything to do with them. Personally I just stay on the safe side and buy series packs and pick up extra packs since the higher mah lipos are typically gonna be more expensive anyway. In the above example the 10000mah pack cost the same as 2.5 5000mah packs. It doesn't take but a minute to change out a pack and then your off and running again. If you have the space in your battery tray and you wanted to bump up your run time without having to change batteries then just make a parallel adapter and use 2 5000mah packs at one time in your kit. then you'll effectively have a 10000mah battery in your kit but when you go to charge them you can charge and balance every cell individually. my .02 on them.
And in the example given above between the 30 and the 40c battery you aren't going to see any different if your esc is only pulling lets say 25C worth of amps. The only time your gonna see a difference between a 30 and a 40C battery is if your esc is drawing more than 30C amps then you'll see a difference because if your running a 30C pack and your system is pulling lets say 42C in amps then your system is going to be starved for power. When you put a 40C battery in there its still gonna be lacking in this example but not nearly as much so you will see more "punch" from the 40C. running a lower C rated pack then what your system is pulling will also cause your Lipos to run hot and can potentially damage them. The C rating isn't how much "Punch" it has, its simply how many amps it is able to continuously deliver. when buying Lipos figure out what the maximum continuous amps is that your ESC/motor can pull and buy a C rating battery higher than that. If you pulling 15C then buy a 20C. If its pulling 28C buy a 30C or if you want to be cautious then buy a 40C so you know that you battery will be able to supply the power required buy you system. The battery is only going to supply what the motor/esc wants....therefore if you motor/ESC is pulling 23C worth of power than your 70C battery is going to be putting out power at 23C. Yeah the 70C battery is capable of discharging way more power than that but it doesn't push its power out, it gets sucked out by whatever rate the motor/esc is pulling it out at.
I know this is long winded but i wanted to get that info out there because a lot of folks have misconceptions about Lipos.
