The wrench's battery is made up of a Makita battery combined with an adapter plate. Because the battery uses an adapter, it can feel a bit wobbly when set down. If your wrench has the same issue, what should you do? If you're interested, you can follow this guide to DIY a battery pack yourself.

For the Dartek electric wrench, you'll need a set of casings and a protection board. You can choose a BAK 2600mAh battery. If your wrench isn't very powerful and only draws 1A at no load, you can make a 3-parallel, 5-series battery pack. That will give you a total of 7.8Ah, and with a 2C discharge rate, that's 15A—more than enough for normal use.

You can also take batteries from an electric bike. Most electric bikes have a battery pack with 78 cells. You'll need to disassemble it and match the internal resistance. The internal resistance is usually around 26–27mΩ, so you'll need to pick out 15 cells.

Next, you'll need to prepare a bracket and place the batteries in it properly.

Once installed, it should look like this:

Then you need to spot-weld the connections.

After that, install the circuit board.

You'll also want to check if the battery level indicator works correctly. If the light turns on, everything is normal.

You can use kraft paper for insulation, like this:

Then place the batteries into the casing.

After the casing is installed, it will look like this. Of course, you can also decorate the casing with stickers if you like.

Here's the adapter battery for the wrench:

And here's a comparison between the two types of batteries:

After swapping in your new DIY battery pack, it will look like this. Compared to the original, the DIY pack is a bit heavier and the casing fits tighter.

With 7.8Ah, it's enough to last about a week of use.

All Done!