Rebuilding Power Tool Battery Packs

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Rebuilding Power Tool Battery Packs

Post by PrIsMaTiC » Fri Dec 02, 2005 10:49 pm

I was just looking at a listing on ebay by a
company called Voltman Batteries. They rebuild
power tool battery packs.

I've been soldering, welding, and brazing big and
little things for decades. Naturally, my first
thoughts were, "if they can do it, I can do it

I opened a dead Milwaukee 18 volt, 2.4 amp hour
pack. I stared at that array of densely packed
cells for a few minutes. I put the cover back on
as quickly as I could!

Now that I've recovered from seeing a bunch
of batteries shoehorned into a tiny box I guess I
should apply some logic to the problem.

First, where do the get the replacement cells that
go into these packs? I assume you can use the old
cells as a guide when you solder together the tabs
on the new cells. Is that correct? Finally, do you
need any special equipment to "shoehorn" that string
of batteries back into the pack?

I hope you can tell that I feel very ambivalent
about the whole thing. If someone tells me they
successfully rebuilt a few of these packs, I suppose
I'll give it a try. Otherwise, I'll probably leave it to a
company like Voltman Batteries.

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Re: Rebuilding Power Tool Battery Packs

Post by jwax » Sat Dec 03, 2005 4:21 am

Like other projects, they indeed can be rebuilt, but the cost/time balance decision is an individual one. Rebuilding a $60 pack for $20 worth of cells maybe worth your time.
Many surplus stores sell cells.

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Chris Smith
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Re: Rebuilding Power Tool Battery Packs

Post by Chris Smith » Sat Dec 03, 2005 9:22 am

The hardest part is the extra [your solder] solder on the tab exceeds the space limits.

Thats why they spot weld the tabs.

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Re: Rebuilding Power Tool Battery Packs

Post by PrIsMaTiC » Sun Dec 04, 2005 8:06 am

If I remember correctly, the entire Milwaukee
drill kit with two battery packs cost me around
$225.00. Home centers like Home Depost want
$80.00 for one battery pack! They're suppose to
last three or four years but they don't.

I should have guessed that the solder tabs would
be spot welded. There is so little clearance
inside the battery case that if one battery is
slightly misaligned all your time and money go
down the drain.

Voltman Batteries wants $35.00 to rebuild a battery
pack. You pay to ship it and they pay the return
freight. I suppose that's the best way to go.

I always feel good when I can do something myself.
Many times you do save money, but you also gain
knowledge which cannot be obtained any other way.
As I've gotten older I've come to the reluctant
conclusion that sometimes it's better to admit that
you're not going to win this one, and give the job to
someone who really knows what they're doing.

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Chris Smith
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Location: Bieber Ca.

Re: Rebuilding Power Tool Battery Packs

Post by Chris Smith » Sun Dec 04, 2005 8:14 am

$35 is not bad. All the ones I have done are a fight to get them squeezed in properly and aligned. Yes, you do learn new tricks after a while, but rarely on the first one.

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Re: Rebuilding Power Tool Battery Packs

Post by Enzo » Mon Dec 05, 2005 8:24 pm

Buy the batteries with the solder tabs already on them. I priced them a while back for some daed battery pakcs. I was looking at Digikey, but never shopped further to look for prices lower. Not only can you buy them with tabs, but they will even put up groupings of them, which may or may not be helpful.

Michael J
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Location: Australia

Re: Rebuilding Power Tool Battery Packs

Post by Michael J » Mon Dec 05, 2005 11:38 pm

I have done a few of these for friends.
Both phone packs and power tools.

They are usually fiddly as hell.
If you manage to crack the case open without too
much damage you are half way there.

Replacement batteries can be obtained with
s/steel solder tags, you need to get that type mostly.

You may also need to drill out the spot welds on
the 2 main battery terminals in some cases, use
a sharp drill around 3 x the diameter of the spot
, don't worry about damaging the battery, it's
dead, protect the terminals.(slow speed drill
lots of preasure - for stainless steel always).

There also may be a thermo fuse, don't damage or lose this.
Draw up a circuit if needed.

Place the new cells on a table in the order you
want them to go, with the tags the way they need
them to be soldered, label everything.
Plan each step, go through how it will go together.


You will probably need a reasonably hot soldering
iron for the tags, they soak up the heat quickly.

Solder " TIN " the tags well before you join them
(lot of heat and solder then flick/wipe it all off the tags, leave thin a film only)
less is better, just sweat them together quickly
without moving them till well set.
Keep the tags as un-bent smooth as possible.

Soldering stainless steel is a pain, use lots of
heat, plenty of resin core solder, and circular
motion, round and round, adding solder along the
way, then when done shake the whole thing quickly
(one wrist snap action) onto a few sheets of newspaper to remove the excess.

Most of the original cells will be assembled into
a cardboard tube, split the tube with a craft
knife, box cutter, etc.
If the old cardboard tube will fit ove the new batteries and still fit back in USE IT.

Be aware of cells shorting when re-assembling,
they can explode,,!!!

Good Luck.

<small>[ December 06, 2005, 04:02 AM: Message edited by: Michael J ]</small>

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