The curve for charging from 20% to 80% is high and battery is big capacity so it normal that will high temp. Please use original charger and cable, also do not share with others device original L5 charger equipment.
DRAM issues still affects S2RAM for energy save. Also Byzantium still not optimized for L5, so thats the reason why every interaction with posh creates high CPU spikes, creating more temperature and battery drain.
Wait for Gnu Crimson and most importantly Gnu Dawn.
Purism