I bought a never-used 31-year-old battery for my T1950CT. The battery is not in perfect condition but is somewhat alive. However, the laptop doesn't "see" it even when started on battery power alone.

With a PSU attached, while the laptop switched off, the laptop recognizes the battery for 10 seconds, the charging LED turns orange, and there is some charging current. But after 10 seconds, the LED goes off, and so does the current.

If the laptop is started after the charging LED has gone off, it doesn't charge the battery. If the PSU is removed, the laptop runs for some minutes on the battery, but its LED is off. When the power drops to 11.3V, the laptop suddenly recognizes that there is a discharged battery, and the battery LED starts blinking.

If the laptop is started within 10 seconds after attaching the PSU, while the battery LED is still orange, the LED immediately goes off, but it still charges the battery. I am currently measuring the voltage, not the current, and I see the voltage slowly increasing from whatever the battery had up to 13.7V, which I think is the maximum for a 12V battery.

But why does the LED stay switched off? If the current is too high in the first seconds and probably too low at the end, there must be some moment when it is just right, so there should have been a moment when it was orange. Also, at the end, when the voltage reaches the maximum value, it should have turned green. But none of these happen.

Is there maybe a utility for T19xx Toshiba laptops that tells anything about the battery status? I haven't found anything in the T1950 manual, but maybe there is one for later models?