Laptop will not run off battery power

I have a Toshiba Satellite R15-S829 tablet PC. It runs perfectly fine on AC power, recognizes the battery in Power Options and with the Toshiba Power Saver software, and appears to be able to charge the battery (though the % may be a bit erratic).

It will not, under any circumstances, run off the battery. It won't boot without the AC adaptor, and if I remove the AC while running, the computer dies. I've tested this with two different batteries, one of which is relatively new.

Does anyone have any idea what the issue might be? My assumption is that something on the motherboard is toast, and that I'm just going to have to turn my tablet into a desktop.

Battery is dieing! Save it!

I suggest you check the electricity of battery before you repair the laptop. if the battery is bad, you can get a replacment one from internet.My toshiba battery was bought from Uk toshia battery shipwordwide site last year, it's worked fine untill now.