Repairing Black and Decker 9074 Screwdriver Battery

Here is the original battery. Three cells surrounded by a soft plastic sheathing

Cut the plastic (I used a utility knife) away.

Now the three cells are clearly visible and the way they are connected in series. Meaning positive from one cell to negative on the next cell. Each cell separated by a rubber insulator

Top to bottom on this image shows the insulator that is on the top portion of the cells. Next are the old three cells and bottom the new cells.

The contacts on the old cells appear to be spot welded to make the connection.

Separate the connections with either a pair of side cutters or a pair of scissor. This will allow you to remove the insulators.

Here all the cells are separated and the insulator removed

Plenty of corrosion visible on each of the old cells.

To prepare the new cells, the heatshrink insulation from the contacts need to be removed. I used a utility knife to remove that.

Here is the first cell, insulation removed. Prepare all cells like that.

Align the positive contact of the first cell with the negative contact of the second cell.

Since the contacts will be soldered to each other, I did use some flux on the contacts prior to soldering.

Apply the flux to the contacts, in my case I used a cotton swab.

Once proper alignment is obtained, I use a alligator clip to hold them in position.

Now solder the contacts together. I used a 30watt soldering iron with a blunt tip.

Here is the first attempt. Luckily I noticed that I had forgotten to install the rubber insulator before going on to the next cell. Desolder the contacts to rectify this.

Here is the next cell properly prepared.

First two cells, separated by the insulator, soldered together.

2nd and 3rd cell prepared and being aligned.

Applied flux and alligator clip to hold it in alignment.

Solder the contacts together

All three cells soldered together, positive to negative end, creating a series connection.

The original battery was wrapped in some soft plastic. I decided to use 1 1/4 inch heat shrink tubing. Black electric tape might work just as well, but I used what I had on hand.

Heatshrink tubing placed over the cells

I placed a clamp from end to end. This will prevent any exposure to hot parts, will allow movement of the battery and still maintain alignment.

Here is the two speed heatgun I use for my projects.

Simply apply constant heat to the tubing by moving the heatgun along the heatshrink tubing.

Here is the battery with the heatshrink tubing attached.

Obviously the contacts are being than the connector. (The corrosion visible on the connector was cleaned of during the installation)

Trim the contacts with either a pair of sidecutters, or like in my case, use a pair of scissors.

Once the contacts are trimmed to size, the battery is ready for installation into the screwdriver. There is a separate guide for that. Total cost for this was around $9.00 for the cells.