Well I wanted to take out the old batteries and install some Lithium-Ion batteries so they would be easy to replace in the future. I decided on a Li-Ion 3.6V 650mAh Rechargeable RCR123A battery. 2 of them in fact. Hooking them up in parallel will equal the original voltage. 3.6 is the original voltage. These batteries will not have the memory problem of the old batteries. You will need a new charger for them because the old one will over charge and you might have a fire. You'll also need 2 battery holders that are the right size for 123A batteries.
Tools you will need:
Dremel tool with cutting wheel
small flat head screwdriver
120 grit sandpaper
Duco cement or equivalent
I think that about covers it.
Step 1: Taking the battery apart
It was suggested by easy-does-it to use boiling water to soften the plastic to remove. This idea should work better. Once the plastic starts to get soft I would think you could just pop it off.
Now that you have it off it is time to use the dremel to cut out the end so we can remove the batteries. Don't forget to use your goggles.
Try and cut as close to the edge as possible. There is a rubber washer on the inside at the end and will probably start to smoke once it heats up. You'll see it once you start cutting in deeper. Remove the rubber washer. Once that is done the batteries should fall out. Just tap it on the table and it should come out. The battery that comes out last will have a metal cup spot welded to the positive terminal. Use the screwdriver to pop it off. Don't bend it. We need it. If the screwdriver isn't working, use a putty knife or pocket knife.
Now you can start cutting out a large slot like you see in the picture. Make it wide enough so you can fit the battery holders. Make sure the battery holders are set in deep enough with a battery installed. You don't want the batteries to be sticking out. Be sure and sand all metal edges so you don't end up cutting yourself.
Step 2: Soldering and assembly
Here is the line up.
The small metal cup is the positive. Solder both positive wires (red) to it. Solder the negative wires (black) to the bottom of the case. The small cup fits in the top of the battery case. I used Duco cement to keep it from moving. You could use super glue as well.
I used a glue gun to keep the battery holders positioned. Before you hot glue anything test it first. Once the hot glue sets, it will be very hard to get to the wires if something is amiss. If it isn't working check your soldering connections. Is the battery charged?
A little hot glue will also hold in the black plastic end cap.
Step 3: Done
Now you have batteries that you can easily replace and for a much lower cost. It also is lighter. It weighs less than half the original.
(edit: Remember DO NOT USE THE ORIGINAL B&D CHARGER TO CHARGE THE NEW LITHIUM BATTERIES)
The down sides are that it may not last as long on a charge as a new one from Black & Decker. So far so good. I've used it on 5 jobs and haven't needed a charge. My old battery would have died on the 2nd job.
(edit: I have found that it lasts about as long as the original battery)
I got the battery holder, Li-ion batteries and charger at
Thanks for reading my first Instructable.
It still works. I am still using the same battery. I have dropped it several times and only one time did I have to bend one of the battery connectors back into place. Since this mod is lighter than the original it doesn't fall out near as often. The red clip ring thing isn't such a good design. It currently stays on the workbench and will only see light duty work anyway.