Revive Dewalt 20V batteries that won't charge


  #1  
Old 01-24-23, 07:12 PM
XSleeper's Avatar
Group Moderator
Thread Starter
Join Date: Dec 2004
Posts: 29,652
Received 1,644 Upvotes on 1,472 Posts
Revive Dewalt 20V batteries that won't charge

This was interesting. I have a couple 5ah Dewalt batteries that I used hard and heavy in cold weather. They both eventually quit taking charges... even though they were brand new, this was only the 2nd or 3rd day I had ever used them. After watching a few videos on it, I sceptically attempted the methods of "repair".

I took 2 pieces of insulated wire (16 or 18 gauge is fine) about 6" long. I put forked connectors on each end of the wires. The batteries have 5 terminals, which are marked on the housing. The outside terminal on the far left is marked B+, the one on the far right is marked B-.

The first thing to try is to jump start them with a good battery. Push the power indicator button on the bad battery. It will either not light up or the left light will barely flicker. Push the power button on the good battery. All 3 lights should light up, indicating the good battery is fully charged.

Now this next part is very important. You are going to connect the 2 batteries with the 2 wires. B+ to B+ and B- to B-. Under no circumstances should the wire ends touch each other! Plug the wires into the terminals. When you make the final connection you may notice a small spark. Wear gloves and don't be suprised or alarmed if it sparks, just make the connection.

Push the power indicator button on the bad battery. It should now light up, indicating a good connection is being made. As soon as you verify it is lit, you can unplug the wires. You don't need to leave leave plugged in for very long. Again, be careful not to touch the ends of the wires together as you unplug them.

Then press the battery indicator light again, and see if your left light is lit, or is at least a stronger flicker than it was. Try it on the charger, and be sure it is fully seated on the charger. If it charges, great! This worked for one of my batteries. But not the other.

For the other, I had to do a manual reset of the batteries. This is a little more technical. You need to remove the 4 T-10 screws on the 4 corners of the battery. Then carefully pry the shell apart. Be careful to not just yank it apart because small wires will be connecting the 2 halves. The terminals click into the upper half of the shell, and you can see two black release buttons, one on each side near the top of the battery. Gently pry these down with a small flat screwdriver and wiggle the terminal block out of the top half of the shell. Then pry the battery pack out of the bottom half of the shell.

What you need to do first is identify the top of each battery (the top has a small indentation around the cap... and kind of looks like the top of a AA battery) from the bottom (which is perfectly flat). Then get the smallest flat screwdriver you can find... the ones in a jewelry set work well. Gently push the screwdriver down into that indentation on the cap of each battery... there is a small gap that you can push the screwdriver into. You may not feel like you are doing anything, but push down on the gap on top of each battery one by one. Half of the batteries will be pointing one direction, and half will be pointing the other direction. Be sure you push down on each one. You "might" hear a small puff of air from one or more cells as you do this. Then reassemble the battery, and push the battery indicator. i was surprised to find that after I did this, I now had a single indicator light on a previously dead battery! And then it would take a charge!

So 2 batteries that were going to get pitched/recycled are now back in service! That's like $200! Glad I tried it, and since it worked for me I thought I'd share! If this helps you, give this post a like!
 
CarbideTipped voted this post useful.
  #2  
Old 01-24-23, 07:29 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 15,115
Received 662 Upvotes on 562 Posts
Sounds very similar to the technique to revive Ni-Cad batteries. I have done this to Ni-Cads but it never lasted and they would always fail after a month.

Are your batteries Lithium? How old were the batteries if it was only the 2nd or 3rd day using them?

 
  #3  
Old 01-24-23, 07:31 PM
XSleeper's Avatar
Group Moderator
Thread Starter
Join Date: Dec 2004
Posts: 29,652
Received 1,644 Upvotes on 1,472 Posts
Yes, lithium ion. The batteries were brand new, but I think using and charging them in very cold weather led to their demise. (Manual states to try to charge them at room temperature) We'll see how long this lasts. Guess I can always try it again when and if they do it again. It literally took less than 5 minutes per battery.
 
  #4  
Old 01-25-23, 07:44 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 15,115
Received 662 Upvotes on 562 Posts
Typically I have found that chargers will not charge a batter that is too hot or cold.

I guess if it was me I would take them back to the store and exchange them since they are brand new.

Good tip though.
 
  #5  
Old 01-25-23, 08:31 PM
XSleeper's Avatar
Group Moderator
Thread Starter
Join Date: Dec 2004
Posts: 29,652
Received 1,644 Upvotes on 1,472 Posts
exchange them
Dewalt sent me 2 replacements... they required photos of the serial numbers as proof... but I still have the defective ones. Figured I had nothing to lose. One of the two is still acting goofy... so its probably irreparably damaged despite my best efforts..
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: