T400 Won't Run on Fully Charged Battery

[msquared]

I have a T400 that's a few years old. I replaced the battery about 6 months ago and it's been working great until last week. Now, the laptop won't run using the battery - it must be plugged into AC. The battery shows as 100% charged; however, if I unplug the power cord ... instant death.

I'm guessing this has something to do with a component that knows how to switch between the power source internally???

I've tried to unplug, leave for a while & plug back in. I have also removed & reinserted teh battery. Nothing changes.

Anyone have any suggestions?

[Drcompute]

Lenovo battery, or generic?

[Mornsgrans]

You only have one chance to exlude the system board as the source of the problem:

Try annother (borrowed) battery!

It happens, that a dead battery shows full charge, Power Manager tells status "good" but the most battery-cells really are "dead". In most cases it happens to "OEM" (replacement) batteries after a couple of months use  but also can happen sometimes with original Lenovo batteries.

[Drcompute]

OEM would be a Lenovo battery.

[msquared]

lenovo battery