Thursday 8 August 2013

Use laptop battery cells to revive old VersaPak electric tools

The original 3.6v Ni-Cd
VersaPak battery
When I was a kid, I loved my tools. Because I was attached to it, I kept my old Black & Deker VersaPak electric screwdriver and electric drill even if the 3.6v Ni-Cd (3-cell) batteries would not hold the charge anymore.
It turns out, a 3-cell Ni-Cd has the same nominal voltage as a Li-ion battery and that dead laptop batteries usually have cells that are still in working order and an appropriate form factor.
This article shows how salvaged laptop Li-ion cells can be used to bring back to life old and dead power tools.

The VersaPak battery modified to hold a 18650 3.6v Li-ion battery

Needed parts & tools


  • The old VersaPak battery (which has not leaked)
    Warning: Ni-Cd is carcinogen, please do not open the casing of a leaked battery and make sure you do not eat, touch a leaked Ni-Cd battery. Do not pierce the batteries inside the casing. Do not do any of this howto on your kitchen counter or your dining table or anywhere not suited. Ni-Cd batteries are toxic, you've been warned...
  • 18650 battery holder (can be found on eBay)
  • 18650 Li-ion battery without protection (or it will not work with the required high current to start the motor). These can be found in most dead laptop batteries (some cells are dead, others not) or on eBay.
  • A 18650 Li-ion battery charger (can be found on eBay as well). You should in any case not use the original charger anymore.
The original battery, a 18650 battery holder &
a salvaged 18650 Li-ion battery (this one is not)


  • Dremel with metal cutting discs (4 or 5 to be sure)
  • Sharp knife
  • Small flat screwdriver
  • Soldering iron + tin
  • A little of boiling water
  • Hot-glue gun (+ glue stick)
  • File (for plastic)

Disassemble the old battery

We need to remove the black plastic cap. Mutantferret explains in his very similar instructable that dipping it into boiling water for a couple of minutes softens it enough to remove it without (too many) problems. Even softened, this remains a difficult step.
Dipping the black cap in boiling water
To remove the plastic cap, gently slip a small flat screwdriver under the cap and turn around the metallic part. I also removed the label, but this step is optional.
Turn around the metallic part with a flat screwdriver to remove the black cap
In the process (I made two of these), I broke one of the two caps. Don't worry if you break the cap a little, it should still fit afterwards.
Broken cap. It will still fit.
Once the cap is off, put it aside, we will need it later.
Original battery with the cap off
One interesting improvement: you could do if you have no 18650 Li-ion charger, would be to put a single cell Li-ion USB charger in the cap. These chargers can be found on eBay.
If you decide to add this Li-ion USB
charger, you simply need to connect
the two battery holder terminals to
the BAT+ & BAT- of the charger
Where the cap was, you can see the end of the last cell of inside the battery casing. With the Dremel (or a saw), carefully cut the back of the casing without damaging the last cell.
Sawing the end of the battery (where the black cap was)
With the rear of the casing cut off, you can slide the batteries out of the casing.
Slide the batteries out of the casing
Depending on where the batteries were produced you might have the chance to skip the following step.
Remove the metallic 'thing' attached to the front of the first cell. Use your small flat screwdriver (and possibly pliers if you need to bend back something). please be careful, we will need that 'thing' later when re-building the battery.
Detaching the metallic 'thing'
You can see on the next picture that the first cell leaked. I should not have opened this one, it is toxic.
With the 'thing' off (you need to keep it for later)
I had to do the previous step for only one of my two batteries. We now have the 3-cell of Ni-Cd battery apart and need to remove the positive terminal (the small metallic cup).
The three Ni-Cd cell out of the casing.
There is a positive terminal attached to the first cell (cup shaped).
To remove the positive terminal, use a knife to carefully detach it (refrain from using pliers or you will destroy it).
Detaching the positive terminal from the cell
Save the positive terminal, we will need it to re-assemble the battery with the Li-ion cell.
The positive terminal detached from the Ni-Cd cell.
We're now now have all the parts and are ready to reassemble the battery.

Re-Assemble the modified battery

We first need to make sure the 18650 battery holder will fit in the metallic casing. To do so, use a file to remove all useless plastic edges that come in the way. In the picture below, you can see that I removed some plastic off the edges of the second plastic holder.
Removed some plastic that was in the way
You now need to solder the positive terminal to the positive (red) wire of the battery holder. The cable should be somewhere around 1 and 2cm.
The positive terminal soldered to the battery holder
Using the Dremel, cut an opening in the battery casing large enough to fit the battery holder (sorry for the picture quality) and insert the positive terminal. Use some hot-glue to secure it.
The battery casing with an opening for the battery holder.
The positive terminal is already in place.
Insert the battery holder in the casing and secure it with some hot-glue. Do not forget to let the negative wire hang at the back of the battery casing. We will need to solder it there.
Inserting the battery holder in the battery casing
Once inserted and secured, make sure the whole thing is cylindrical and remove the excess plastic with your file.
Some plastic of the battery holder still needs to be removed.
We will now solder the negative wire. I made a small notch in the casing to solder the wire to it.
Negative wire soldered to the casing.
Make sure all your connections work before puting the black cap on.

Test your new battery

When I first tested my battery, I was surprised to see that it would not work. This comes from the battery shown in the picture below which has an over-current protection circuit... which kicks in when the motor of the electric screwdriver starts (it uses more current when starting). You will therefore probably prefer to use unprotected 18650 batteries for this application, or even better... recycled battery cells from a dead laptop battery.
The whole thing assembled and ready to be used.
This battery will however not work as it has an over-current protection
Et voilà !
Using an unprotected cell in the electric screwdriver.