My past experience with lithium polymer powered hobby helicopters taught me that lower charging rates helped battery longevity and possibly battery cell balancing. Does this hold true with the Tesla battery? if I am not in a hurry, or want to charge directly from my solar panels, I have lowered charging rates to 15 to 25 amps. By doing so, charging efficiency drops from the low 90% range to the low 70% range. Anyone have opinions on why efficiency drops with lower charging rates and if the lower rates help with battery health or balancing?