Battery drain

[Easty1968]

Hi guys I have a cheap Chinese xgody g14 as a second phone, it is one of these rugged waterproof android phones that I use for work as i m a builder. For a cheap £80 phone it is great apart from one thing every day the battery will go from fully charged to dead in half an hour, if I charge it after I'll last all day, but it means I have to Carry a power bank around every where I go, it's doing my head in have tried everything ,its running on android 6 any ideas ?