If you own a Samsung Galaxy Mini and it looks like the battery has died, you can do a few things to make your smartphone work again.
If the contacts of the battery and the contacts of the phone (those three golden pins) are not clean, the phone might be dead because it won’t receive power from the battery.
What you can do is to clean the pins from both the battery and the phone with a electric contact spray. You can spray the contacts or just spray on a tissue and rub the golden pins.
Leave them open to dry.
Insert the battery, close the back and start the phone. If the battery is drained, put it to charge.
Usually the battery will work again.