Lithium ion battery troubleshooting

Question

I'm not sure if this is the right place to ask as it is a computer problem, but I'might thinking it's the battery and so I want to ask some questions regarding that. The battery has been deeply discharged and I think that's the issue.

My ultrabook battery rated at 11.1 volts. When I measure the voltage on the battery now it's around 9.8 volts. Is this voltage too low for a lithium ion? So each cell is probably around 3.3 volts instead of 3.7. When I connect the battery to the motherboard and charger, it jumps to about 10.3 volts. When I measure the connector on the motherboard itself (with charger attached but no battery) it shows around 0.8-1.0 volts. So the charger is providing 1 volt to the battery.

The charging port and motherboard soldering points are measuring at 19.3 volts (19 volt adapter). So the port itself is working. The battery itself already had one dead cell in it, but it was working okay until yesterday.

So my question is is it likely the battery is to blame? It seems to me that the charger to mobo is working, mobo to battery leads is working (albeit at around 1 volt--does that sound like it's working???), and yet no matter how long I leave it charging, the bare battery nor the battery while charging won't reach 11.1 volts (although it does climb from the lower numbers I stated above to as high as about 10.52 volts). Does it seem conclusive that the battery is not accepting charge from the motherboard?

Edit: the ultrabook in question is an Asus zenbook ux31la. Looking back I recall being able to use the device without a battery but I'm not sure. Some research online suggests the zenbook line can be used without a battery so now it might be a bad power port. Which wouldn't make sense because I'm measuring 19.3 volts at the soldering points for the power port. I just don't get it. There's no way the mobo died it's just too big a coincidence this happened as my power adapter died.

Answer 1

11.1V means that this is a 3S battery. In other words, the battery consists of one or more sets of cells, each with three cells in series. In your case, there is one set of three cells, or 3S1P.

While 3.3V per cell is low, it is not exactly a bad voltage for lithium-ion. However, if the voltage of any cell is well below 3V for extended periods of time, you may have cause for concern. If you are able to measure individual cell voltage, chances are good that once of the cells is not able to reach full voltage. If a cell has failed, there is probably no way to replace it since it's probably of the polymer type, which means you'll need to replace the whole battery.

Deep discharge, especially to below 2.5V per cell, is likely to result in damage to the battery. Attempting to recharge a cell that is deeply discharged for more than brief periods of time can result in a fire.