How to test li-ion batteries

[narindia16]

Hello Friends,

I am having some faulty Laptop Li-Ion batteries. I was willing to do some R&D of these batteries. I opened the batteries and found 6 Samsung cells inside that and a small piece of PCB (I think it is li-ion protection circuit).

I checked the specification of the cells on internet and found that it should be of 3.7V but when i removed one from the bank it was 4.1V. Then doing the same with each other cell, it was all 4.7V.

I want to ask you all, is there any machanisum that i can check which cell is faulty??? Normally voltage drops when cell becomes dead, but why these cells are giving higher voltage??

I want to know the way to check laptop battery and its cell....


Thanks
Narinder Pal

 

[ard]

Hi,

This is quite straightforward. Those cells you refer to usually have a ma-hour rating printed on them. So, you discharge the cell thru' a known resistance and measure the time it took for the cell to get to a point where it would be considered 'flat (around 3 volts for this cell)'. This would give you the actual ma-hour rating of the cell, as against the manufacturer specified one (current drawn*time taken in hours).

Regards,

Anand

Added after 7 minutes:

Forgot to mention, the voltage readings you took seem to be without a load; these are bound to be misleading and not indicative of the health of the cell.

Regards,

Anand