Lenovo X Series X121e ThinkPad :: Error Has Occurred - The Battery Cannot Be Charged

My battery (FRU: 42t4957) is stuck at 2% and refuses to charge:

I kept it at 40-50% most of the time by changing battery threshold. Total cycle count was about 80 (84 now) first use date 2013-03.

On Saturday I tried to run a "discharge-charge-discharge-charge" cycle (by watching some movies) to reset the gauge of my battery. During 2nd discharge my laptop hibernated due to low charge much earlier than expected, when I turned it on it showed that the max capacity is 28 Wh and the battery is in the "poor" condition.

I tried to perform automatic gauge reset but didn't get much (29 Wh). I updated power manager and performed another automatic reset which failed too.

So I tried to make a manual reset and left my laptop paying a movie for a night. On Monday I plugged my AC adapter in but found out that the battery won't charge: "a battery error has occurred the battery cannot be charged".

I cleared residual capacitance by pushing the power button several times and reset the BIOS to defaults but got nothing.

If this problem can't be sold I would like to know the reason of it to avoid such things in the future. While googling this forum I met contradictory opinions on battery reset: ones say that it's extremely harmful because battery "doesn't like" to be discharged to 0%, others say its harmless.