R31 main battery charging problem

[Vasa]

Hello Thinkpads fans,

I've my R31 more than 4 years with full satisfaction. A year ago the main battery died completely (system unit didn't even know that battery is connected - MaxiMiser showed No Battery is attached) and now finally I got the new one. But now system unit is not charging battery at all. When system unit runs on charged battery MaxiMiser shows all info about discharging, actual wattage, time etc. but when I connect AC adapter system unit starts to run on AC but do not start to charge main battery. But... the LED status indicator works as the system unit is charging fine.

Any clue how to find out what is defective? (I guess that MB died as well...)

Thank Vasek.