Hey.
So I am having a problem with my battery on my laptop. A Lenovo X201T with i7 CPU 8GB RAM and 256GB SSD. I used to use Win 7 until 2015 but now use Linux Mint 20.3.
The battery started not showing up any percentage in the task bar any more in about 2016 and would instantly shut off if I unplugged the AC because it always said 0%.
So I stopped using the laptop but the battery appeared to charge still just fine and I always kept it topped up every month or two.
So I got the laptop back out to use it again now and had the same problem.
I opened up the battery and the C and D (I assume clock and data) wires had come detached from the BMS PCB.
I re-soldered these wires and checked all the cells voltages, all about 3.6-2.9V. I topped them all up one at a time using a single cell BMS until they then all charged up to about 4.1-4.2V so looks good.
The laptop battery now shows a make and model number so the data wires are working whereas before it did not show anything at all. But it still only says 0% despite me leaving it in the laptop on AC for a few days.
So I decided to order a new battery. I installed it, it was at 0% for a few mins then started to charge now it shows 100%.

However when I do not have the AC adapter plugged in the laptop will not work.
I cannot turn it on unless on AC. If I unplug the AC while the laptop is running it shuts off even with a full charge.
Any ideas how to fix this?
