Samsung i900 problem?

Just a quicky... I have a samsing i900 omnia. Several yrs ago the screen got broken. the phone would still switch on.
I decided to replace the screen to have a spare phone. changed the screen no probls, I plugged it in and let it charge for 1/2hr. I switched it on but I get nothing. I measured the voltage on the battery totally 0v. I checked the charger and it pumping out 5v ok. so I plugged in the charger into the phone & removed the battery on the phone and measured the votage at the contacts on the phone and there 0v. has anyone seen this before? I tried measuring all other phone I can find and there 4.5v aprox at terminals.