3G battery not holding a charge?


New Member
Dec 3, 2010
Plymouth UK
I have this old 3G which used to go dead after a very short time(about 5-10 minutes) So I ordered a new battery from eBay and a new back cover which had seen better days.
I set about fitting the new battery into the back cover and transferring all the other components, carefuly screwing them into place. I have replaced a back on a 3G before so I had a pretty good idea of what I was doing.
All was assembled and switched on and Hey Presto! I still have the same fault!
I gave the battery several long charges and the big green battery symbol shows its full, but when I disconnect the charger it will only last less than 5 minutes and the battery shows empty and the phone shuts down. If I reconnect the charger it shows full again.
I've tried various resets and iTunes restore but still no good. I've also tried the charger from my iPad which is a 10watt charger but that makes no difference. I suspect a fault in the charging circuit but how can I check this?