Thomson #242740 ac adapt./bat.charger

[mowzalot]

I was hopeing to recieve some help in finding out if a diode might be the problem. The battery only charges to 4-volts. There is a + and a - pin on the charger, but there is also a pin marked "t" that is in the middle of the other two. I've tested it with a multi-tester and recive no voltage between the pos. and neg., but recive 2.5 volt between the neg. and the pin marked "t". There is a refresh button on the charger that doesn't seem to work. I have opened the unit up and tested the diodes (in board) and found one that has continuity in both directions. There is an ac jack on the side of the unit that tests 8.5 volts and would like some input on if I were to take a jumper from the pos. on the jack to the pos. on the charger, if the voltage would be to high to charge the battery safely?