Instructables
Picture of How to rebuild a Dewalt 14.4v battery pack
$80 for a new battery pack.

$25 to build your own.

Plus bragging rights!!!
 
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Step 1: Take apart battery pack

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remove the six screws that hold the pack together

carefully pull apart the two halves

take notes as to where things are and how they go back together

have a digital camera on hand for documenting dis-assembly

Step 2: Remove battery "pack"

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carefully pull the battery pack out of the holder

Step 3: Document everything

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as you pull the battery "pack" apart

take pictures and draw pictures of how the 12 batteries are packed and connected so tightly

Step 4: Buy replacement batteries

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Google 1.2v subC batteries

(1.2 * 12 = 14.4)

find your best price for 12 batteries

when you place your order make sure you have measured your battery cells and are getting the correct "physical" size

buy with or without tabs

without tabs is less expensive and the following steps will show you how to make your own tabs

Step 5: Diagram the connections

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you will notice after folding and unfolding the string of batters

that the 12 batteries are wired in series pos-to-neg, neg-to-pos and so on

use the gummy insulator that you pried away from the top and bottom of the batteries to draw a template

then use a coin to complete the circles representing the batteries

draw a diagram looking at the batteries from the bottom

then draw a diagram of the batteries from the top

note each connection and how the battery tab is oriented

number the batteries on your diagram

while you are waiting on your new batteries to arrive in the mail

practice refolding the old battery string and placing it back into the holder




 

Step 6: Making battery tabs

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the battery tabs, as you can see, need to be flexible

one very good source of material for making battery tabs is an old computer cable with an outer mesh

this is an old Firewire cable cut into small strips with the innards removed

the mesh can be squashed flat and take on solder very well

you will need eleven strips

cut extra just in case

put some flux on both ends and tin the ends with solder in preparation for soldering to your new batteries
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Good work !
Beanal1 year ago
Use a small screwdriver to pry out each of the12 NiCad cells from their battery compartment. Some are soldered as this provides a better connection and helps stop the cells from shorting. If they're soldered, heat a soldering iron and touch a soldered cell terminal with the soldering iron until the solder melts. Remove the soldering iron and quickly pry the cell away from the connection before the solder hardens. You must do this on all 12 cells.
http://www.drill-battery.com.au/batteryshop.php/dewalt_power-tool-battery.html
boomchuck1 year ago
Thanks for creating this DIY! I have an 18v Coleman that came with two batteries that have since crapped out (after less than a year). Couldn't find replacement batteries. With this DIY I can now I can replace the innards of a perfectly good cordless drill.
I have one question, though. Should I get the 2900mAh or the 1600mAh sub-Cs? What's the difference?
boomchuck1 year ago
Thanks for creating this DIY! I have an 18v Coleman that came with two batteries that have since crapped out (after less than a year). Couldn't find replacement batteries. With this DIY I can now I can replace the innards of a perfectly good cordless drill.
I have one question, though. Should I get the 2900maH or the 1600maH sub-Cs? What's the difference?
RangerJ1 year ago
Two observations:
One - there is a good chance only a few of the batteries are bad. I have repaired battery packs by making two weak ones into one functional pack. This is accomplished by charging both and letting them sit for a day. Take them apart and measure voltage on each separate cell, marking it on them with a felt pen. If the cells are 1.2 volts, you are good. If 1.1, weak, and below that no good. Take the bad ones out and replace with good ones.
I have had success with Craftsman batteries in years past - I don't know if they are still the same or not.

Two - I have tried to repair DeWalt batteries and couldn't get the insulators off the top and bottom no matter what I did. At the best, I could break it into pieces and remove them. At the worst, they broke and still stuck to the cells.

Anybody got a solution to that problem???
gezer2u2 years ago
I was really refering to sub C batteries. Their size makes them a rather big heatsink making it a lot harder to over heat them to the point ofexploding. I have seen them explode from using a device called a battery zapper that uses a capacitor and high voltage to break up shorts in the battery thus lowering the resistince in the battery and increasing the voltage. They sound like a stick of dynamite! Lol

I think a button battery is different because It is very small and can over heat rather quickly. I wonder if the CMOS battery exploded because it is lithium. Lithium is a whole different thing.

I too agree that you need a soldering iron that is big enough to stay hot while soldering the battery. I was trying to make a short comment and figured someone else would say it. :)
DeWalt battery packs are NiCd and not NiMh?
Another trick I use:
Take a cheap RC model battery pack with compatible voltage and capacity, and fit about a four foot lead to the power tool terminals with a matching plug.

Then I can just drop the battery pack in my pocket, and conveniently use the power tool with much less weight in my hand.

Then also, with an appropriate socket fitted, run it from my car battery charger when in my workshop.
ksickafus (author)  ElectroFrank2 years ago
like!!!
Thanks !
I forgot to say: when running a battery power tool from a car battery charger, only if it is a compatible voltage ! 

If the car battery charger is a slightly lower voltage, the tool will run a bit slow.

If its a higher voltage, the tool runs faster, but give it regular breaks to cool down or it will overheat !
jamesvs400a2 years ago
will have to make an instructable when i re-build my battery pack for my drills. not going to be as simple as yours though. (lithium batteries with cutoff circuit/custom charger.

note that the fast charger is what kills the batteries. best thing you could do is redesign the charger. got an ozitto 20.4V drill that slow charges then cuts off power to the battery pack when charged to prevent overcharging. batteries have lost capacity from new but still has heaps of torque after 8 years. makita nicad drill and both battery packs are fancy paper weights. :)
ksickafus (author)  jamesvs400a2 years ago
waiting . . .
Wildrat2 years ago
This is a good instructable, unlike instructables to cook cake in a microwave or how to make a sweater for your gerbil out of an old sock. Good Work!
ksickafus (author)  Wildrat2 years ago
thanx
gezer2u2 years ago
Nice job with the instrucable!
Some things to clear up.

I know a thing or two about nicad and niMh batteries. I have soldered hundreds and hundreds of batteries. I have raced battery powered RC cars for many years. As in any racing everything counts and I battery powered RC cars, batteries are everything. For instance look up "worlds fast RC car" :)

That said, batteries won't explode from soldering them. Getting them too hot will affect the life and capacity. There is a vent in the pos. side that vents gas's as the cell charges. If it gets damaged then there is a possibility that it can explode.

I think the reason that the factory battery is spot welded is because it is faster then soldering.
YES Soldering them can make them explode many of us on here have seen it happen, just because you havent experienced it does not mean it wont happen. That is akin to saying heart attacks dont happen from over exertion. Factories Spotweld because spotwelding limits the amount of heat generated, soldering allows the caps to sink heat into the cell where damag CAN take place. IF you can solder steel you can solder rechargable batteries. But it isnt the same as soldering an electrical circuit. The single biggest key is using an iron of high enough wattage so that the area you are tinning is limited in diameter and doesnt sink into the cell. Too small of an iron (wattage) and you end up over heating the battery as the area you need to tin doesnt heat fast enough in relationship to the heat spreading into the battery. SO yes Speed is imperative, be it weld or solder connections.
If you ever take a good look at a design tech or engineers work bench, you will notice multiple soldering irons, the biggest differences will be in wattages, even if they have a good adjustable station, they will have atleast one or two high wattage irons on hand for dealing with high amperage power connections, which tend to heat up, and as such need to act as heat sinks to prevent themselves from becoming "desoldering devices", the only way to solder these types of devices such as highpower mosfets and similar, is with a good old fashioned high wattage soldering gun of several hundred watts or better... well rechargable batteries are about the same type of beast. I myself have made a spotweld "gun" to weld solder tabs onto batteries using an inverter type stick welder, I clamp the ground connecton in place with a small modified C clamp hold the solder tab with a hemostat and hit it with the spot gun and in less than a second it's done... then the tab (made of nickel) can be easily soldered to with no worries using the apropriate sized insulated wire, And NEVER EVER forget the original thermal fuse!
ksickafus (author)  sschoemann2 years ago
good comment
ksickafus (author)  gezer2u2 years ago
correction . . batteries WILL explode! Read below. I was replacing a small CMOS computer button battery with no experience, little patience and a huge soldering gun.

BOOM!! The battery exploded!

After changing my pants I made a mental note that IS ALWAYS in the back of my mind whenever I solder batteries ... eye protection, patience, slow as she goes, common sense, etc.

I have soldered hundreds since. No explosions, and all projects are still in working order.
Hec031 gezer2u2 years ago
I agree with this conclusion. The spot welding is simply a mass production process and not some kind of restriction on soldering. Many rechargeable batteries come with their metal tabs soldered since they are made by workers in developing countries.

Money says the batteries last just as long as the factory one or longer. Time will tell.
ksickafus (author)  gezer2u2 years ago
I've only exploded one battery while soldering . . .

wet my pants!

but, it was a small button battery for a computer CMOS.

WEAR EYE PROTECTION!!!!

and it took a very long while to explode by someone who didn't know what they were doing

that's why sites like this are nice

so . . . I agree

you are not going to explode the battery by soldering

a spot welder would be nice

but this is the duct tape solution for those who don't have one
If the battery is no longer very functional, there may be only one or two cells that are bad. Before replacing all cells test each to see which are deficient. Replace only those that are defective and no longer hold a charge. Cheaper yet.
ksickafus (author)  enivels119622 years ago
cheaper yes? But for all the work in this project why not change all 12 and just keep the "old" good ones for some other project?
Your idea may save a couple of bucks and be a good idea in a pinch, the problem is you do not know how much capacity is left in the used batteries unless you you discharge them with a known load for the required time. If you have it apart and ordering batteries go ahead and replace them all, not unless of course you build a simple capacity tester. Your idea will work if your stuck or funds limited.
to test them all you need to do is throw a lightbulb across the battery and check the voltage... no big deal no wasted effort and no viable batteries in landfill polluting the ground water...
papagun2 years ago
It has been my experience that soldering heat devastates the cells. That's why they should be spot welded rather than soldered. The battery will work for a short time after this sort f repair, but the heated cells will die pretty quickly... certainly the battery will not last as long as a commercially repaired or spot welded one.
My personal experience would support this.
Unfortunately, Not many of us have access to an ultrasonic welder.
ksickafus (author)  sconner12 years ago
that's why you are on this site . . it's for people who have duct tape and paper clips
Papagun, you are absolutely correct on your observation. Johnson Control had issued a white paper on this at one time. I no longer have a copy, and can not locate a copy online, as I no longer have access to the corporate data base
Hi! I'm really glad I saw this, although I had worked out most of it myself, the heat question I had not anticipated. I was told by a seller on Ebay that usually, not all the cells in a pack go, and to test each one before replacing the lot?
I have about four of these in pieces, and I feel the cheapest way is to find a cheap one, and replace the string as a whole, eg, looking at Ni-cd 18v pack, I see a replacement power pack for only £7.80 on Ebay, so I'm going to buy it and try to re-fit it in a different case as an experiment, this would be far cheaper than buying all the individual cells, as they are at least £1 each!

Moving onto the heat question, I have seen low temperature solder for sale, but haven't tried it yet. Any ideas?

I'll report any findings!

In accordance with the "be nice" policy, "You are all a wonderful group of intelligent, handsome, fair and fastidious people and it brings me the greatest pleasure to interact with you,

Love and Kisses, Hugs and Blessings!!!"

Richard Lakin-Inzunza
it isnt the temperature of the solder that is the issue. it is the characteristic of the metal you are soldering to. If the surface of the metal does not open molecularly, the solder will not adhere to it, Low temp solders are designed for copper based metals not steel or nickel, further the fluxes used to get the surface of these metals ready to accept the solder will attack the lowtemp solders and break them down over time. The proper solder to use is actually a silver bearing solder, however, this creates another issue, as sliver bearing solders have highrt melting temperatures. Sometimes you just cant win.
Just a thought. One could use fine sandpaper to Clean the surfaces to let the flux do it's job quicker and easier with less heat transfer.
ksickafus (author)  sconner12 years ago
yup! I used my Dremmel(sp?) wire brush to "skuff" up the battery ends. After tinning the ends of everything, soldering was quick!! The drill works great. And. I have only charged it once since doing this. Holding charge very well. Just the experience was worth $25, even if I shortened the battery life. Without a spot welder you gotta go with what you have!!
ksickafus (author)  Ricardo da Vinci2 years ago
just do it! and let us know how the LT solder works!
ksickafus (author)  Ricardo da Vinci2 years ago
true

but I thought

if I am going to go through all of this

why not just replace all 12 cells?

in my case

I didn't get a good reading from any of my cells anyways

do all 12 is my advice
here is another point, charge them all seperately but before you take the pack completely apart. Quite often one cell will drop low and prevent the pack from charging. If the cell is just discharged but not damaged, this will quite often take care of the whole issue. Providing you have a 1.5 volt charger you can tap across the low cell.
And remember, you WONT get a good reading on any of the cells if one of them is completely bad, unless you know how to test for a shorted or open cell and locate the bad one. An open cell will prevent any of them from taking on a charge, a shorted cell will overcharge the rest, but shorten operating time. Also if you have Nicads, and have not been completely discharging them before recharging, you may be fighting the dreaded memory effect and have ruined most of the cells in the pack. For this reason, when I've replaced cells in power tools I've always went to NmHi but added a ballast resistor on the charger socket to slow the charge down accordingly as they charge faster than nicadsm and can over heat if too much charging current is applied.
sconner12 years ago
When I do this I check the voltage of each cell, then the entire pack to be sure before I put the pack in the charger or tool.
One backwards cell will be bad. so double check everything.
ksickafus (author)  sconner12 years ago
agree!!
BillybobT2 years ago
Having built Battery packs for RC cars in the past, I can tell you that the resistive (read that again, RESISTIVE) welds make for poor conductivity and lost power. This Instructable is right on the money by using solder and and the mesh tabs along with lots of flux. Makes for nice clean connections. Well done.
ksickafus (author)  BillybobT2 years ago
thanx
Sorry son but I have to call BS on your comment. Since EVERY factory made high end cordless power tool has the battery connections arc (spot) welded on your comment is pure hogwash. ALL ARC (SPOT) welding forms are RESISTIVE welding as you put it...
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