Rebuilding Batteries for Cordless Tools

From what I know, a good battery for your cordless tools is not available on the cheap side.

This is the reason that I use, for my home, only tools connected to a 120V mains.

There is a company that says they do this. I got their name off a woodworking forum. Nobody there had actually used them. So, buyer beware! But, you might try one to see how it works.

http://mtobattery.com/store/page22.html

I have to ask.

Do you religiously charge and discharge the batteries fully each cycle?

Don't want to sound like your mother, but this is important.

I've got to say it is a good feeling when you rip out the expired cells from a cordless tool and replace them with nice fresh ones at 1/4 of the price of the battery replacement.

That said. I gather you want to do this yourself - it's not too difficult.

The first task is to determine what kind of batteries (or cells) the battery pack is using - normally Nicad or Lithium. Try to get similar capacity even though you will be tempted to go bigger (the charger may not cope). eBay is a good source of cells or a local(ish0 electronics shop.

Note the comments on total discharge - true for Nicad - not so true for others.

See if you can get a matched set of NiMH replacement cells physically like the NiCads. Same size, same solder tabs, that will fit or just get the upgraded battery packs for the tools.

They beat the NiCads in every way. I wont buy NiCads or stuff powered by them.

Jon

Ya you can do that. Open the case (take pictures) and notice the batteries are encased in rubbery envelope, cut this open (take pictures), remove the leads from the dead batteries. Buy new lithium's and reattach the leads, band or duct tape the batteries together again and replace in the case.

Viola`

6 NiCad or NiMH cells or two big Lithiums. That is the question.

If there is a pair of Lithium cells (7.2Volts) in it, or if you put Lithiums in, you have to be real careful not to damage them in any way and, and for darn sure, don't leave a way for moisture to intrude. You will have a fire. Overloading or charging at a high rate can shorten their life.

One reason I like the NiMH and Lithium Ion because they don't have as much of a "memory" problem as the NiCad.

Nickel Metal Hydride ( NiMH ) batteries can be stored for many months in a charged or discharged state without any detrimental effects as long as they are not exposed to extreme temperatures for any long period of time. Nickel Metal Hydride ( NiMH ) batteries stored charged or discharged recover their capacity within two or three charge / discharge cycles.

Lithium-Ion batteries:

The lower energy dense manganese-based lithium-ion, also known as spinel, maintains the internal resistance through its life but loses capacity due to chemical decompositions. Spinel is primarily used for power tools.

Keep the Lithium-ion battery cool. Avoid a hot vehicle car. For prolonged storage, keep the battery at a 40% charge level.

During use they don't like to be fully discharged. Don't keep going with the idea that you can get that last operation done before exchanging the pack.

Jon

Or three not so huge lithium's

I was thinking of the 7.2 Volt Lithium that uses 2 cells.

What were you thinking of?

Jon

4 x http://rechargeable.minamoto.com/item/17335R.htm

or

4 x http://www.batteryjunction.com/uf16340.html

Hi,

I lost some "no name" Ni-MH batteries by early failure - maybe charging not correct.

These at being fully charged go down in voltage!! and any charger that does not detect this will overcharge and destroy these after some cycles.

Then I switched (guving me a push to spend some more money to Sanyo: much better.

Now available as Sanyo ENELOOP: will not degrade in charge over months if stored fully charged.

Try and judge.

RHABE

There is quite a race on to out-do the competition in the battery business.

Sanyo has been doing well.

Tschuess,

Jon

You may want to check out some Radio Control Sites. I know my friend Jeff rebuilds his battery packs for his flying toys. Not sure if you can call a RC Bomber with 15' wing span a toy or not, and that's just one of his planes. But he buys his batteries in bulk & makes his own packs. He says he saves about 55% by doing it himself.

As said elsewhere, soldering will destroy the cells. Industrially they are spot welded.

Also, your packs include an overcurrent protection, can be a resettable fuse (Polyswitch) or a fusible link.

This is important.

If you choose to replace the cells, go for good quality, low impedance cells. Else you are wasting your time and money.

My experience with cordless tools is do not go cheap.

I had a B&D 18V drill for witch a pack was dead. The form factor for this was the same as a Dewalt, so I recharged the dead pack in a good electronic Dewalt charger and it revived it. The B&D charger was pretty much a transformer and diode scheme, not good.

So a gave my B&D away and got a Dewalt and still use my formerly dead battery pack.

Also I came across a 12V B&D drill witch had a problem killing its battery packs. As it turns out the drill was driving too much current and breaking open the fusible link. Useful not to set fires.

Newer systems using Li cells should be best for you, if you choose to change systems. They are lighter and have a better power density, more power in less weight and size.

As implied by several posters, the best tips are:-

1) Do not overcharge. Cheap chargers do not know when to stop...also, if it were possible, each cell needs to be individually charged!!! For best results...impossible I know, so make sure that when you buy cells, get all at the same time from the same manufacturer and the same charge(build), to keep things as even as possible.

Never mix manufacturers, nor age of batteries.....even of the same type and manufacturer....

An occasional recharge of the individual cells in an intelligent charger will reduce the differences and also show which ones are weakest/strongest....

2) Do not run completely down (completely discharge), this usually reverse charges the weakest cell(s), making it(them) even weaker and more likely to fail.

I don't want to sound like an advertisement but there is at least one company here that will open a "spent" battery and replace the guts for less than a new the cost of a new battery. They do lots of business with local contractors. They are an old family owned company (Dueitt's Battery Supply in Mobile). I think you can get the parts if you want to do it yourself. They could not do my Dewalt because it is held together with a metal pin they can't or won't cut. They said if I pressed, drilled or cut the pin, they would repack it. (I have not done it yet)

I have heard that there is at least one other in the area that provides a similar service.

Good luck,

Paddler

It was the battery debacle that tipped the scales for me to equip mainly with pneumatic tools and because there is more power to be had in a lighter completely rebuild-able tool.

Select tools are cordless with rechargeable batteries and I do replace the old cells myself.

In addition to Ross' question, If one is to rebuild the battery using a different type of cell would he need a different charger? Rationally, I would think that charging voltage is charging voltage, but I may be over looking a practical aspect of battery charging.

I have an old cordless Makita drill that I love and would like to rebuild the batteries with NiMH or Li Ion, but I have hesitated due to doubts about the charging issues...

Frustrated with batteries I have also gone to mainly corded tools, but who wants to crawl through the attic or run around a large wood working project with an extension cord in tow?

A charging voltage is only a charging voltage with Lead acid batteries, all others use a charging current!!!

Also, with ALL batteries, charging beyond "full" just causes damage and is a waste of energy.....serious damage WILL be caused.....

There is no excuse for my ignorance......accept my most humble apologies...

How would you determine the parameters in order to charge another type of battery correctly?

http://electronicdesign.com/Articles/Index.cfm?AD=1&ArticleID=8493

http://powerelectronics.com/power_management/power-peripheral-battery-based-ic-0506/index1.html

Ya need a smart charger for lack of a better term.

DO NOT replace NiCad or NiMH cells with Lithium-Ion (Li-Ion) cells UNLESS you obtain a battery charger designed for Li-Ion! There is a very real risk of fire!