hi

i want to make my laptop work off the battery because the original cells inside the pack exploded. (they never worked in the first place)

The pack is for a compaq lte-5000 laptop and it is a 12volt 4ah smart pack.

i do not want to search the internet only to find packs priced at £110.

i want to put new cells inside the pack (ten 2000mah nimh cells)
but i am unsure if:

a) the laptop will charge up the new cells
b) i will need a dedicated charger to 'condition' teh batteries
c) if it will be reliable or loose connections will prematurely power off the laptop.
d) if the battery life will be satisfactory/crap

will it be ok to use nimh cells purchased from a retail store, or will i need solder tagged versions?

or any recommendations or directions on what i should do?

First of all, there's no such thing as a solder-tagged battery cell. They cell tagged NiMh cells, but you have to spot weld them together, preferably with a thermal shunt. Otherwise you use too much heat (soldering takes longer than spot-welding) and you will break the batteries (typically causing a shortened battery life, but sometimes fire or explosion).

So I think untagged are probably the way to go. You'll have to get some sort of holder or spring to keep them tightly in place somehow; the power terminal connections must be kept tight, always metal-on-metal.

Loose connections will power off the laptop unless you can connect another battery (or big capacitor) of equal voltage in parallel to take up the slack when the connection breaks. Not having loose connections in the battery in the first place tends often to be the easier approach.

All NiMh cells are rechargable; as far as I know there's only one way to recharge them and so the laptop should work. You won't need to condition them because NiMh cells have no memory effect (unlike NiCd).

I hope that you don't need me to tell you that using a home made battery will almost certainly void any warranty you have on the laptop.

Look at the electronics suppliers such as digikey or mouser, they can weld the cells together for you.

i stuck a battery from a r/c car in one of my laptops. in place of the original battery. worked fine, however the the battery powered time of the laptop was considerably shorter.

i thought about replacing the original cells in the battery pack, however i came to the conclusion that for the amount of work involved with getting the things soldered/spot welded, the time waiting, and even the time involved in shipping the things, the r/c car battery was a much simpler way to go. plug and play so to speak, and much cheaper since i found the appropriate voltage battery on sale !

i don't have any voltage monitor or anything like that either. for an old laptop though, it works and keeps me happy