Apple iPhone 3gs sometime got battery problem it drains battery quickly within some hours while battery shows full indication in such case we have to use charger many times.
For solving this problem we have to consider these steps carefully because iPhones hardware section is very difficult to handle. So follow these strep carefully:
1. First try to change data cable and charger then check battery backup
2. Then try to reset mobile using setting then check problem
3. If still no luck then use next hardware tricks
4. In mobile we have two charging capacitors those work is to control charging function some time they had internal shorting so due to that we get false charging so remove two charging capacitor as shown in yellow mark in image
5. Then apply jumper from that point to direct battery point then problem will solve.
6. After all done we will get proper charging and battery backup but there is one disadvantage of this jumper that we cannot see charging process during process.
After applying this solution take care about charging time that we should not exceed more than 2 hour because over charging can damage battery.