Hot Rodding a Power Drill Battery

So, your power drill battery dies. What now? Fork over 85 bucks for a new one? I don’t think so. After searching high and low on the internet for a good price for a replacment battery I found the retail for my Black & Decker 14.4V to range from 35-85 dollars. Riiiight. Time to make your own!

At this point it would be good to mention you should really discharge the pack before you continue. Don’t play with electricity unless you know what you are doing!

Step 1: Let’s Find Out What Is Inside!

I had a little brainstorm and decided to open this thing up and see what makes it tick. It’s funny, I always thought there would be some mystical magical component of power tool batteries that justified the outrageous prices…you know, custom made or ethereal glowing lights or little elves or something. Turns out they are just a rip off.

Fortunately for me the internals were looking familiar, a simple set of “Sub C” rechargable NiCd cells from my RC car racing days. I used to build my own racing battery packs so I couldn’t help applying that here.

I had visions of using power tool batteries that power world championship RC cars and transform my moderately powered B&D; into a drill that would make screws and yet-to-be-drilled holes tremble with unspeakable fear.

When you open the battery you’ll need to save some plastic bits detailed below. Don’t break them.

Step 2: Replacement Sub C Cells

At this point I came back to reality. The racing batteries alone would cost a hundred bucks. So, I settled on a brand name NiCd cell from GP. The main difference from the stock batteries is that these are 2000 mAh cells and the stock ones are only 1700 mAh…so I should get more run time…basically a bigger gas tank.

In case you aren’t good at math, a 14.4 battery takes 12 1.2V cells to make up a pack.

Step 3: Battery Bars

Next up on the bill of materials are some RC parts. These 24k gold plated battery bars are from Novak racing. I couldn’t skimp everywhere. A bag of 28 was about $14.00 from Tower Hobbies.

I only needed 10 to assemble one pack, but I have another drill battery waiting do die. So, that’s five bucks for the bars and up to $26.48 total. Still ten bucks shy of the best retail price I could find  Incidentally that price was direct from Black & Decker.

Step 4: A Bit of Wire…

Finally we have some 14AWG high flexibility silicone wire from another RC company.

Just had this lying around and I only needed about 3 inches so let’s call it free.

I would recommend using good quality wire here. Your battery will only be as good as the weakest link. I prefer not to have any weak links. This will also be a likely spot for a meltdown if your wire is not up to the task.

Step 5: On to the Assembly

I paried the cells and bound them with electrical tape just to make them easier to solder together. These buggers are a little hard to hold on to.

Don’t forget to tin both ends of the Bosch cordless drill battery before you try and attach the bars. A drop of flux and a drop of solder, not too much though.

I should mention that you will need a pretty serious soldering iron to get this job done. Don’t overheat the battery…kind of a catch 22 here.

Step 6: Now the Tricky Part…

After getting the battery assembled I removed the electical tape. The bars are very rigid and have no problem holding the pack together. Soldering the bars on and getting everything to line up is the hard part. Be patient.

The real tricky part is the cell that sits on top of the pack.(red wire attached) This top-most battery sticks up into the shank of the battery case. The little black plastic bit houses the stock connectors that mate with the actual drill and charger…so save that and be careful not to brake it.

The top battery needs to be attached to the battery direcly below it and sit slightly offset. B&D accomplishes this with another plastic part that I tossed. I used one of the stock battery bars that I pulled off the stock battery pack since they were thin and flexible. Both batteries were soldered to the sock bar while they were sitting next to each other. Then, to move the one onto the top, I just folded the battery bar in half…clear as mud…I guess I should have taken a picutre. Finally I wrapped the bottom of the top battery with electrical tape to prevent any shorting.

Step 7: You’re Done!

Well, that’s it. Took about two hours from start to finish and it went back into the case quite nicely. The Novak battery bars came with stickers. I love that, so I put a Novak sticker on this one so I would know which pack was my uber pack. Charged it, put it into the drill and it runs like a champ.

You can hear the difference compared to the stock Milwaukee power tool battery. This puppy is just begging for some heavy drilling. Time to pull some screws out of a big crate.

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