Thanks all

Hi Dodgey, I have the same thought as you that it should charge around 1 hour before getting warm. But the fact is it starts to get warm(after 5-8mins) to hot(estimate 50C)gradually until the charger switch to slow charge mode(after 45mins)

My charger is TLP-EXpro, LCD Display show it charges at 10.8V
, current at 0.5A, but output capacity stop at 600MA.

Thanks again.