Atlas Informatik How-To

Pimp My Cordless Screwdriver


Recently the lights on my (admittedly older) Black&Decker® VP7251C cordless screwdriver resp. drilling machine went out. Or to put it another way: The VersaPak™ batteries had exceeded their lifespan. Not only that, but they also caused the charger to burn out.

As an occasional do-it-yourselfer you immediately have the idea how to save the still fully functional screwdriver. Replacing the charger would still be easy. But the batteries were Black & Decker® proprietary. During research on the Internet I found out that a single original battery should cost about 75 €/$. There were also "generics", which should cost "only" 15 €/$. And that still without dispatch. You could buy a new cordless screwdriver. But this disposable mentality is not my thing.

During the research I came across the YouTube video "Black & Decker Versa Pak Pimpen". Many thanks to the authors, you helped me a lot!

I have applied the same principle now to my tool. Here are the infos to it, so that it could become also a success for you:

So, first I needed 2 Li-Ion batteries and a charger. I decided for this battery set with charger (not to be taken as an advertisement, there are many other products) plus Swiss plug. Cost: approx. 15 €/$.

Tip: This charger has separate charging electronics for each battery. Since the determination of the end of charge for Li-Ion batteries is important, but also somewhat complicated, you should not charge them with a simple battery charger. Reasons for this see here.

By the way: Forget the labeling of the batteries. The mAh specification is simply exaggerated. Dx on the other hand says the truth in its article description. They even measure it in their own workshop before writing it on the website.

Which I found out only later: Only unprotected rechargeable batteries are suitable as replacement batteries for this machine. They have no protection against overcurrent. Apparently the cordless screwdriver needs a little more current at high speed than the safety circuit releases. In my case the missing protection circuit never led to a problem.

Since I had no flex, I bought a cutting disc insert for my drilling machine. Costs were also approx. 15 €/$.

In order to put the new batteries in, you first have to remove the black plastic caps. They are very tight. Heat the caps all around with a lighter or hairdryer and they can be easily loosened.

When cutting open the VersaPak™ batteries, you should always wear gloves and a good mouthguard. It is almost inevitable that you will saw into the Ni-Cd batteries inside. And cadmium is an environmental poison. So the sawdust and batteries should be disposed of afterwards in an airtight plastic bag in the battery waste. Tip: To ensure that the cutting disc is held on the metal sheet, first stick an adhesive tape over the line to be flexed.

The best way to get the three old cells out is to cut the connection between them with a knife. Unlike in the video, I did without the holder for the new batteries. You can also simply solder the batteries in. You should be careful to heat the batteries only as briefly as possible and cool them down afterwards immediately. In order for the solder to grab quickly, sand both ends a bit with fine sandpaper. Then solder the round cap on the positive pole. At the back solder a wire as thick as possible, put it through the hole, bend it over, solder it. Put the cap on. Already finished.

Now to the charger: Unscrew the charging station. Then disconnect the previous charger, cut off half of the cable and insert it into the charging station parallel to the existing one. Solder so that each VersaPak™ socket is led out individually.

Now unscrew the new charger and pull the cables into the already existing recess. Solder on at the large solder points (spring ends).

Details for the conversion of the charging station are listed here in more detail.

And already we are finished. Just plug the batteries into the VersaPak™-station and the charging will start automatically. The LEDs indicate this with red and jump to green when finished.

So what have we actually achieved now?

  1. We had fun doing handicrafts (;-)

  2. Since the self-discharge of Li-ion batteries is much smaller than with Ni-Cd, our cordless screwdriver is almost always ready for use without charging. That was always a nuisance.

  3. We have now approx. 2200 mAh energy instead of only 2100.

  4. We have added an intelligent charger with end of charge indicator which will extend the life of the batteries.

  5. We can simply replace the batteries again, if they should get tired again. And at a sensationally low price.

  6. We have an additional charger for Li-ion batteries at home. These are often found in flashlights.

  7. We have only spent 30 €/$.

  8. We don't have to dispose of a fully functional device and thus protect the environment.

Update December 2021

I could use the device for 8 years now without any problems and it still works perfectly. But now the FandyFire 2400 mAh batteries became weak and had to be replaced. I bought two new Sony VTC6A for about 5$ each. I chose these because they won a competition where they provided the most current. Replacing them was a breeze. It even has the advantage of increasing the power to 3000 mAh. Unfortunately, it also has a disadvantage: the end-of-charge indicator no longer works with these batteries. You have to manually disconnect them from the power after a few hours. When you order your new batteries, remember to make sure that "unprotected" (no overcurrent protection) is in the product description. If someone finds a battery where the charge indicator still works, please send a short message to "mail [at] atlas-informatik [dot] ch". I can then write it in here.

My tip: As a general rule, I have now found that the best and most reliable batteries come from these countries: Japan, South Korea, USA. With the other countries, I have all too often been fobbed off with lousy quality. Especially with Chinese products, the battery was often completely unusable after a short time. With cell phone batteries it was even worse: they began to swell. A major safety risk and nuisance, and also unwise for a good future of earth.




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