Replacing battery cells (power tools)

Kingchip

Hi Guys,
I hope this is in the right forum or someone can direct me to the right one.

I have 3 dead batteries from my cordless drills, I've stripped the batteries and tested the individual cells. On 2 batteries there is only 1 dodgy cell each so I want to take cells from the 3rd battery and replace them.

The thing is 2 of the batteries are 15.6v 3.5Ah nimh(13 no 1.2v cells each) but the 3rd battery I want to use the cells from is 15.6v 3Ah nimh.

Can I use the cells with a different Ah rating?

If not does anybody know where I can get replacement cells?

Thanks in advance.

cgarrad

ebay for the cell, they are normally spot welded together though.

Kingchip

Thanks for the reply. Is it better to spot weld rather than solder?

Hootanany

Can you do this lithium batteries.

DublinDilbert

If the new cells come with 'tabs' spot welded on them, you can solder these tabs to the tabs in your battery.

You won't be able to get enough heat into the battery for soldering properly, this is why they are spot welded.

Kingchip

DublinDilbert wrote: »

If the new cells come with 'tabs' spot welded on them, you can solder these tabs to the tabs in your battery.

You won't be able to get enough heat into the battery for soldering properly, this is why they are spot welded.

Thanks for the reply, do you know if I can mix the cells with the different Ah rating?

DublinDilbert

Probably best not to mix and match different aH rattings as they will charge and discharge at different rates.

The problem is batteries have got better, so the newer ones will have a higher aH rating.

Get as close as you can with the ratting

Bruthal

Kingchip wrote: »

Thanks for the reply, do you know if I can mix the cells with the different Ah rating?

As DD says, its not a great idea. Smaller cells will over discharge in use, and overcharge in the charger when mixed with larger AH ones. Not good with lithium batteries.