I've brought a HP NC4200 on eBay. Other than a few COSMETIC issues it works fine except:

When the LAPTOP is off, the charging LED is solid and the battery charges fine.

When the laptop is on and the charge is around 0-10% or around 50% the XP battery icon is constantly jumping from AC Charging, Just AC and battery. Other times it works like it should do, solid LED and the AC charging icon.

Same thing happens in Xubuntu too.

The laptop runs fine without a battery so it can't be a connection issue with the charger lead/plug.

I thought it may have been a BIOS issue, so I updated the BIOS to the latest version, but the problem still persists.

Any ideas? The electronics in the smart battery aren't smart enough. This is a very common occurance among laptops and has been an issue for at least 10 years. They can never seem to fix it or don't care to.Could it be fixed by replacing the battery?If the battery holds a charge and functions, why WOULD you want to replace it? I had 2 identical laptops and 1 would do the same as yours and the other was normal. Swapped batteries, same thing. It's REALLY a communication issue between the laptop and the battery. Is the problem in the laptop or the battery? It's hard to say, unless you try different batteries. But laptop batteries are very expensive.That's if I can even get a battery anyway, all I can FIND are unofficial Chinese batteries, dunno what they're like.

Thanks for your help, much more helpful than HP's solution of "Reinstall Windows".
I guess I'll have to disable the battery notifications.I wouldn't buy one.