|The original 3.6v Ni-Cd|
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|
|Turn around the metallic part with a flat screwdriver to remove the black cap|
|Broken cap. It will still fit.|
|Original battery with the cap off|
|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
|Sawing the end of the battery (where the black cap was)|
|Slide the batteries out of the casing|
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'|
|With the 'thing' off (you need to keep it for later)|
|The three Ni-Cd cell out of the casing.|
There is a positive terminal attached to the first cell (cup shaped).
|Detaching the positive terminal from the 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 batteryWe 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|
|The positive terminal soldered to the battery holder|
|The battery casing with an opening for the battery holder.|
The positive terminal is already in place.
|Inserting the battery holder in the battery casing|
|Some plastic of the battery holder still needs to be removed.|
|Negative wire soldered to the casing.|
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.|