Power tools have come a long way. It used to be you needed extension cords or a generator for your tools, but now you can get just about anything with a nice rechargeable battery pack. As it turns out, most of those packs are made by the same company, and [syonyk] wanted to see how similar two different Makita packs and a Rayovac pack were. What he found was surprising. The outsides were very similar, but what was on the inside?
The Rayovac pack was easy to open and had a controller, a thermal cutoff device, and two layers of 18650 batteries. The similar Makita pack looked identical from the outside until he tried to take it apart. The maker had plugged one screw hole and used security screws instead of the Phillips heads like on the Rayovac.
Once open, the insides looked totally different. The battery management board was larger, potted, and connected to the battery using nickel strips instead of soldered wires.
A smaller Makita pack should be about the same with a single layer of batteries. Makes sense, right? It does make sense, but it isn’t true. There was a much cheaper board inside and the cells used didn’t even match the published spec which is decidedly naughty.
Despite the markings, not all of the packs met their rated specs. The Rayovac pack for example may have had a slightly higher output voltage. The small Makita didn’t meet its Wh rating. Even two packs from the same company didn’t have anything near the same innards, and while the larger pack was well constructed, the smaller pack looked a little slipshod for many reasons covered in the post.
Maybe these toolmakers should hire [Timothy Economu]. If you want to see the guts of a much bigger battery, take a look at this Tesla Model 3 pack teardown.