Hi!
I look on LiPo charging reference schematics and cannot understand why there is a low side MOSFET needed. For example http://www.ti.com/lit/ug/sluu447a/sluu447a.pdf Q1 and Q3 are obvious, they do PWM for charging LiPo via inductor L1. But what Q2 and Q5 are for? I they have to discharge battery for storage or something, then assume there must be some powerful resistor, not short circuit via transistor like now.