HOW TO - Refilling laptop batteries

No chance of voiding your warranty I suppose.

Greg

I understand all laptop batteries are secured to prevent cells from over charging.

Re: HOW TO - Refilling laptop batteries

Replacing the Li-Ion cells in a battery pack with larger ones is not really a good idea.

The electronics in the pack are designed to work safely with the cells that came with it. The electronics talk with the system that is charging it. It tells the charger the charge voltage it requires, the max charge current it can tolerate, it's present RSOC (relative state of charge) and other information. The pack also tells the charger when it has reached it's charge limit. atthis point the charger stops all charge current. A Li-Ion cell can not tolerate a Trickel charge. The Li-Ion cell can be very dangerous if not handled carefully for several reasions:

1. In most other rechargeable cells, such as Ni-Cad, the electrolite is water based and not flammable. in the Li-Ion cell It is flammable.

2. Unlike Ni-Cad, a Li-Ion cell does not have a specific end of charge point where it will accept no futher charge. A Ni-Cad, once it is charged, will convert the excess charge current into heat. The Li-Ion, on the other hand, will continue to charge as long as the charging voltage exceeds the cell open circuit voltage. As the cell voltage of a Li-Ion cell exceeds approx. 4.2 volts, more or less, depending on its chemistry, the Lithum in the active material will start to plate out as metalic Lithum. When this happens the Lithum starts forming dendrites, little points of metal. These little points will eventualy will puncture the thin membrane seperating the anode and cathode of the cell. Once this happens, a direct short developes and all the energy stored in the cell will quickly heat the active materal and the electrolyte. Once the cell temperaturer reaches about 160C° it will go into thermal run away. In other words, the cell ruptures and the now flaming electrolyte goes everywhere along with pieces of the metal case.

Putting Unknown cell in a battery pack may cause the above sequence of events to happen. You may be putting together a bomb and not know it.