One of my projects require a hefty amount of amperage - and as such I want to use 2 LiPo 2S batteries, in parallel. In addition, I am regulating the voltage using multiple DC-DC step down converters ("UBEC" - https://www.hobbyking.com/hobbyking/store/__4319__TURNIGY_3A_UBEC_w_Noise_Reduction.html).
The 'trivial' approach would be to use parallel the batteries while being used (and charge them separately). Does this present potential cell imbalance issues/dangers? How does this behave with the multiple DC-DC converters?
Since I am using at least 2 DC-DC UBEC converters, I was thinking maybe I can get away with just connecting the 2 batteries negative terminals together, having each battery power half of my load. Would this work? Do I need to join the negative/"ground" terminals at the battery or after the DC-DC converters?