This instructable was inspired by this one by ikssk, except I didn't want to buy a whole bunch of new cells. Instead I used a BIGGER battery from an Uninterrupted Power Supply unit that I had in my possession already.
The power tool I have is a Hitachi DS 12DVF3 which came with a flashlight. Silly of me I lended the screwdriver to a friend and very soon one of the batteries started to misbehave. It could no longer power the drill because it was only able to hold up to 11 volts. The flashlight worked somewhat OK, but this is of almost no use to me. Thus, this project.
Step 1: Disassemble the Old Battery.
Disconnecting everything: with caution please. It will zap you if you're not careful – battery cells sent visible sparks with sound toward an carefulness dismantler. Make sure you don't short them... Also, the connector pad is very fragile in this particular drill. I broke it and had to use super glue and hot glue to put it back into its original position.
Step 2: Assembly of New Cell & Drill
Putting the battery head back into the drill minus the old cells.
Drilling a bunch of holes for nylon ties and wires towards the new battery.
Connecting the new battery.
Testing: device operational
Testing: charger operational
Adding hot silicone and tying the new battery up with nylon ties.
Aesthetic touch: using Duct Tape for better protection and look : )
Oh, and short video here:
Yes, It's a bit heavier now and my right arm is a bit stronger :)