Why is my battery draining so fast on my Star S9920?

[alancaz]

When I use my Australian sim my battery drains from 50% to 0% overnight even with the phone turned off. The phone also has problems sending and receiving calls and texts. It even drained my portable 4400ma charger overnight once.
But, here's the rub, when I fit an Indonesian sim everything works fine and the battery lasts 4 days.

 

[Rukbat]

With the Australian SIM in, look at Settings/General/Battery after the phone's been sitting for a few hours and see what's using most of your battery. It's probably the cell standby, and that's probably because you don't have a very good signal.

(BTW, you should be charging the phone once it drops down to 40%-60%. Allowing it to drop to what the phone calls 0% (it can't - at about 0.5%, the battery disconnects from its terminals internally. Charging a fully discharged lithium battery could cause an explosion.) shortens the battery life drastically.)

 

[alancaz]

I have just checked battery use with Indonesian sim; phone idle = 49%, cellstandby = 48%, screen = 2%.
Why would the battery run down when phone is off overnight?

Optus Australia stated...The phone is using the wrong frequency, Optus only has 900 & 1800. I checked and the phone has 850, 900, 1800 & 1900 on 2G.
Another phone I have (mtk6515) from same chinese supplier works fine on same frequency's.