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How to rebuild an 18 volt DeWalt Battery

Posted by Brad - the battery guy on September 30, 2010

As most people have seen, you can buy a book for roughly $6 that will show you how to “Bring your dead battery pack back to life!”  But unfortunately, for any of us that have actually tried the method that they show you, it doesn’t work.  They basically tell you how to zap your battery pack with 24 volts and it will make your battery like new again.  I don’t suggest buying those books to anyone.  It’s a waste of money.

I decided to start a blog, and show people how to properly rebuild batteries, and answer any questions that people may have about the subject.  My name is Brad.  I own a battery repair shop in Escondido California called FixMyBatteries.com.  I have built virtually every type of cordless tool battery you can think of, and they are basically all the same.  So the method that I describe in this post, will work for any type of NiCd (Nickel Cadmium) or NiMH (Nickel Metal-Hydride)  battery pack.

The first thing you need to do is get the cells, nickel strips, and a size T-10 Torx bit for your screwdriver or screw gun.  I use an industry specific spot welder to rebuild batteries in my shop, but I am going to assume that most people will be using a soldering iron.  If you don’t have a soldering iron, you can pick one up at any electronics store for about $20.  You will also need rosin core solder.

Step 1:
If you look at the top of the 18 volt DeWalt battery you will find that there are screws holding it together.  Remove the screws from the top of the pack and carefully remove the lid from the base of the pack.  Inside you will find 15 – 1.2volt Sub-C size cells. Remove the top of the DeWalt Battery pack

Step 2:
Carefully remove the insulation from the top and bottom of the battery cells.  You will see that the battery cells are connected Inside the DeWalt 18V batterytogether using strips of nickel from Positive to Negative (wired in series) which is what creates the 18 volts of electricity.

Step 3:
Carefully remove the top cell.  To do this you will have to break off the piece of Nickel that connects the bottom of the cell to the rest of the pack.  Then you will see a wire goes from the black connector down to the pack and is connected to the positive terminal of one of the cells.  Using your soldering iron, remove the thin black wire (the Thermistor) from the side of the top cell.

At this point the only thing still connected to the top cell is the connector for the drill.  Using something flat, like a putty knife, pry up where it is connected to the battery cell.

Step 4:
Now you have the pack disassembled.  Set the pack on the table, and next to the pack, set up your new battery cells in the same configuration as the old pack.  Its not a bad idea to tape or glue the new cells together, so when you’re soldering the nickel tabs on, you don’t move the configuration of the cells.

Step 5:
Use a marker to write on the top of the new cells, marking the way the nickel strips connect the batteries together.  It’s important that you do this part correctly.  If you make a mistake and complete the circuit on the new cells, you will most likely burn yourself, and you will defintely ruin your new cells.Have your battery rebuilt by the pro's!

Mark the top and the bottom of the battery pack.

Step 6:
Use your soldering iron to solder the nickel strips in place.  If you have never used a soldering iron before, it’s a good idea to google it!  Whatch a video or two to make sure you know what you’re doing first!

Step 7:
Replace the insulators on the top and the bottom of your new pack.

Step 8:
Connect the positive termial of the top cell, to the negative terminal of the pack with nickel and solder.

Step 9:
Solder on the black connector to the negative terminal of the top cell.  Be careful not to use too much solder because if you do, you will have a hard time getting the battery pack to fit properly in the case.

Step 10:
Solder the thin black wire on to the side of the top cell.

Step 11:
Solder the white wire on the front of the battery connector to the positive terminal on the pack.

Step 12:
Put the pack in the case and replace the top of the case.  Be careful not to tighten the pack too much or you will likely strip out the screws and the pack won’t stay together properly.

And that’s it.  You’re done!  Put your battery on the charger and make sure it is charging properly.  If it is not, then you probably did something wrong, and will need to re-trace your steps and make sure you followed the instructions perfectly.

If you have any questions feel free to comment.  If this seems like to much of a pain….you can check out my website at http://fixmybatteries.com, follow the simple instructions for ordering a battery rebuild and I will do it for you!

Unfortunately, I don’t have a camera in the shop, so I only had a couple of pictures to put up…..but I will be adding pictures to go along with the instructions over the next couple of days.

Be Careful…..and Good Luck!

4 Responses to “How to rebuild an 18 volt DeWalt Battery”

  1. Paul said

    Thanks Brad, sharing your knowlege on the battery rebuild is a selfless and condiderate gesture, and greatly appreciated by a tradesman as myself. Blessings to your business. Regards Paul R Falcone

  2. Brad i have bin trying to do this and got as far as taking the screws out of a 18 volt dewalt but stopped then because i was unsure how to proceed right now i have 3 that need rebuilding i will try again now that i read your post , Thanks a lot i really mean that .
    Pete.

  3. Such an informative article! Thanks for sharing! :)

  4. Robert G S Plant, E8 USN, (Ret) said

    Many, many thanks for the instructive post. That information saved me a lot of money. Buying new batteries really damages the wallet! If there is any opportunity for me to send you some business, I certainly will do so! You sharing of information is the finest gesture in business practices. It will surely improve your business. Thank you, again.

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