I just got a new super brain 960 and 3800 mAh battery. my friend used the charger to charge one of his batteries but when i plug in my batterie the voltage goes down and say it has completed the charging but the v reads 3. something. any ideas?

Hi, welcome to RCU. Lets make sure we understand the trouble and make sure it is being started properly.

Plug charger into AC or DC and it powers up.
Plug battery into it and reads battery voltage.
Push start, voltage should start to climb.

It seems like perhaps your doesn't charge at all.