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How to revive or recondition cordless power tool batteries

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Pod
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How to revive or recondition cordless power tool batteries

Post by Pod » Wed Nov 30, 2016 10:46 am

Thought I'd share my experiences with power tool batteries. No doubt I'm not the only one who has gone to use one of these tools, only to find that due to lack of use (or charging :wink: ), the battery is flat?

Often, the charger will not want to charge a fully discharged battery. This can be remedied by connecting up the flat battery to a 12volt car battery charger for a few minutes. Once the battery has taken a little charge, it is often possible to switch it to its normal charger, which will work as usual. Please note that I take no responsibility for the cordless battery exploding etc, so don't leave it on charge for too long!

If this fix fails, it is possible to dismantle the battery pack. Inside, you will find a number of cells (in my experience, "sub-C" size, rated at 1.2v) which are connected in series, the number depending upon the voltage of the battery pack. For example, a 15.6v battery will contain 13 cells.

These are available on ebay. I bought the 13 I needed from China for about £16 including postage. Not only was this much cheaper than buying a new battery pack (if available!), but saved me from having to throw away a perfectly serviceable and expensive power tool.

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Re: How to revive or recondition cordless power tool batteries

Post by conez0 » Wed Nov 30, 2016 3:44 pm

Not the sort of thing I'd expect to see on BigCoupe, but this is great. I've done this for cordless tools and my Roomba.

For those that dont know what is going on when the battery drops below a certain charge level the internal impedance goes up so high that the charger no longer "detects" the battery.

I hook mine up to a variable bench power supply and dial in 110% of the battery voltage (e.g. 13.2v for a 12v battery). My power supply you can set a current limit so I'll set to 0.5A and charge for twice the number of Amp-hours. So for a 2400 mAh batter I'd charge it for 4h 45m.
1984 BMW 633CSi

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olympia57
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Re: How to revive or recondition cordless power tool batteries

Post by olympia57 » Wed Nov 30, 2016 6:58 pm

Good thread .
I had a Polish guy working with me recently and he had a full array of power tools that he had modified to run on Lithium Polymer (LIPO) batteries .
He is heavily into building and flying model helecopters and drones and used the batteries that he was familiar with on the power tools . Their battery performance was impressive .
His English is reasonable but technical translation was difficult and when he mentioned that there was a possibility of explosion or combustion if the correct charger and charging method was not employed , I rapidly lost interest ...... :shock:
We have to complete another job within the next month so I'll take some time to accurately ask what is involved and the costs therin.
1981 635 series 1

Pod
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Re: How to revive or recondition cordless power tool batteries

Post by Pod » Fri Dec 02, 2016 11:35 am

conez0 wrote:Not the sort of thing I'd expect to see on BigCoupe
But this is the "workshop" section! Does everybody else either use air-powered or corded tools on their cars :-k

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Re: How to revive or recondition cordless power tool batteries

Post by sansouci » Fri Dec 02, 2016 5:52 pm

I've used Primecell to rebuild my 12v dewalt power packs. They are on the web with applications and pricing.
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Re: How to revive or recondition cordless power tool batteries

Post by hornhospital » Fri Dec 02, 2016 5:56 pm

Air tools, mostly. When you have one of these, it's a given that air tools will be part of the arsenal.
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'84 633CSi "Sylvia"; '85 635CSi "Katja";'87 325is "Odette"; '93 325is "Elvira"; '95 M3 "Ashlyn"

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sansouci
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Re: How to revive or recondition cordless power tool batteries

Post by sansouci » Sun Dec 04, 2016 12:57 pm

hornhospital wrote:Air tools, mostly. When you have one of these, it's a given that air tools will be part of the arsenal.
Ken,
Is that sitting inside your garage? If so, how do you deal with the noise? I've seen some neat enclosures in garage.journal.
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Sansouci
84 E24 633Csi Auto, Bronzit/PearlBeige 6997510
93 E32 740il M60 Auto, Alpenweis/Ultramarine
60 535i M30 5-speed Green/Beige (crushed)
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Re: How to revive or recondition cordless power tool batteries

Post by hornhospital » Sun Dec 04, 2016 4:54 pm

It's under a lean-to behind the shop. It's actually pretty quiet...especially considering it was built the same year I was, 1951. WABCO (Westinghouse Air Brake, now Wabtec) makes some incredibly durable stuff. It's held up a lot better than I have.

It's a model 3YC with a 125 gallon receiver. 25 CFM @ 90 psi. I run it at 90 cut in and 135 cut out. I had to have something that big for testing locomotive air horns. I also have three media blasting cabinets that take a lot of cfm. One really big one with aluminum oxide media, and two smaller ones (the ones that Harbor Freight sells) with plastic beads in one and glass beads in the other.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'87 325is "Odette"; '93 325is "Elvira"; '95 M3 "Ashlyn"

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Re: How to revive or recondition cordless power tool batteries

Post by GRNSHRK » Mon Dec 12, 2016 6:05 pm

OK, pretty sure I have this problem with my Craftsmen drill/driver, 19.2V version :roll:

So looking at the battery pack, there are 4 "conductors" on the end that fits into the charger :-k

Just exactly where does one connect the battery charger terminals :-k

Photos would be great, I can snap a shot of my battery pack as well, if that would help [-o<
:mrgreen:
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Re: How to revive or recondition cordless power tool batteries

Post by Pod » Tue Dec 13, 2016 8:31 am

GRNSHRK wrote:OK, pretty sure I have this problem with my Craftsmen drill/driver, 19.2V version :roll:

So looking at the battery pack, there are 4 "conductors" on the end that fits into the charger :-k

Just exactly where does one connect the battery charger terminals :-k

Photos would be great, I can snap a shot of my battery pack as well, if that would help [-o<
My battery pack was the same. Two of the connections went to something which looked like a capacitor(?) which may be to reduce rf interference(?).

The easiest thing for you to do is split the casing and all will be clear. Mine had tamper proof triangular-head fixings, but they came out easily enough. HTH :wink:

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Re: How to revive or recondition cordless power tool batteries

Post by Brucey » Tue Dec 13, 2016 7:53 pm

re connector identification; look inside the tool, and you will usually see that only two of the three or four pins connect to the tool itself. These are the power connections.

If you have a voltmeter, set it to some low DC voltage and probe the connections. Even a really knackered battery will show some voltage on the relevant pins.

FWIW, the extra connections to the battery are usually a sensor of some kind, eg a temperature sensor (for NiCd or NiMH) . This reports back to the charger and it ought to prevent the battery from being overcharged; several different cell types are both damaged by being overcharged and/or being to heat up when they are being overcharged. If you rebuild a battery pack this sensor should be reinstated in exactly the way it was originally. To be sure, it is best to measure it/test it to make sure it is still OK.

Obviously if you rebuild a battery pack with different cells (either by type or capacity) then there is no assurance that any of the usual things that might help the batteries charge sensibly or not set themselves alight in the charger etc are definitely going to apply.

BTW you can call me a cynic if you like but I have seen very few battery packs in commercial power tools etc that are genuinely robustly designed, in that they all charge cells in series. This leads to the very real possibility of unbalanced charges, and all kinds of weird problems if one cell in a series stack starts to self discharge.

I recently reviewed my collection of defunct cordless power tools and by far the most common failure has been the batteries. But then again I have also had motors fail, gearboxes clap out, electronics fry, and chargers go wonky. Between the lot of them I have spent enough money to have bought another 6er.... #-o

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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