I have recently bought a used X240.

You can charge it e.g. during the night when it is turned off and then use it during the day.

However if it is about to run out of battery while you are using it and you connect the charger, it turns the screen off and on repeatedly, so that you can not use it. This seems to be the case unless the battery is at 99%.

Any ideas on what could be wrong with it, or how to solve it?

I have tried anoter charger and anoter battery, but it is still the same

i have recorded a small video of the error here: https://www.youtube.com/watch?v=L29OZQil4y0

Best regards

I've seen a similar issue and it was caused by the power saving options on the X240. Have you checked those? Also, what happens if you recharge it ouside Windows? If it still occurs then it would indicate a hardware problem. If not, it's something to do with Windows.

Thanks for your suggestions.
I have checked the power saving option. There was nothing unusual just different thresholds, which I tried to adjust to give a bit more gab, but it did not help.
Not sure what you mean when you say that we should try to recharge it outside Windows.
But I could try to boot it on e.g. a Linux USB stick, charge it and see what happens.
Anyway I contacted the person from who I bought it, and after he tried another battery and another charger like I did, he offered to swap the 'case' to another.
So basically we got another X240 where our hard drive got installed, and it is now works fine.
So the problem must be linked to the hardware and not Windows in this case.