It sounds like a motherboard problem. It’s likely there is a dead component (probably MOSFET) that prevents the battery from charging. It could also be the ‘switch’ battery pin on the motherboard is grounded which is why the laptop thinks battery is still connected. From what you’ve said I’d say the charging IC is dead as that would stop the charging and tell computer incorrectly that battery is still connected. However, I’m just going off limited info so it might be something easier to fix.
From your description it seems the battery is not charging at all but the laptop can still run of mains power. Is that correct?
- As with most fixing, let’s try simple, easy and reversible things first before doing anything drastic. Try and enter your bios with battery connected and see if there is any battery monitoring tools in there. Repeat with battery disconnected and see if laptop still thinks the battery is present. This will determine whether the battery detection circuit is working properly or not.
- Next easy step is to remove the bios battery (if present), hold power button down for a minute then put battery back in and see if that fixes it.
- You can test voltage on the motherboard battery pins when charging by using a multimeter on Voltage test setting. Leave battery disconnected but test voltage of each pin with power cable plugged in. This will tell you whether the power from your charger is reaching battery or not. See if you can find a pinout diagram for your battery. Sometimes battery will have labels with a + or – indicating polarity of battery and which pins are which. Normally you have positive and negative pins on opposite sides and the data pin in the middle. Red wires are positive. If there’s no voltage or low (<12V) at the positive pins then you know there’s a problem further back, most likely a dead MOSFET or charging IC. If you do have power there, repeat test with battery connected and check you still have power getting there. If you have power getting to battery then the battery should be charging. If it’s not then there’s something very odd going on.
- To check if there’s a short at the battery connection somewhere, disconnect power, battery and CMOS battery (if present) Use a multimeter and test each battery pin on the motherboard to see which are grounded. See if you can find a pinout diagram for your battery to work out what each does and which ones should or shouldn’t be grounded. If any are grounded that shouldn’t be, then, if you’re lucky, it may just be something simple that can be fixed easily. Check for easy things first like corrosion or burnt out missing traces or components nearby. If the short is somewhere in an IC chip then you’d need someone experienced to do the repair.
Without the laptop in front of a fixer it’s pretty hard to diagnose. It’s most likely a short or a dead component of some sort on the motherboard which means unless you can find it and replace it there’s not much hope for a fix.
