I have a #Ryobi #battery that refuses to charge. After many months of ignoring the problem and not using this battery, I decided to open it up and see what’s inside.
There are 5 security screws, one of which is hidden by a plastic plug. The plug is made of hard plastic, so I managed to mangle it enough while trying to pry it out that I won’t bother reinstalling it when I’m done. #electronics
After removing the 5 screws, the shell can be removed. The inside is rather complex even though Ryobi is very much on the budget side of the power tool spectrum.
On the bottom, there are 5 #18650 Li-Ion cells connected in series. The board on top seems to regulate charging and prevents over-discharge.
I poked around with a multimeter, and I concluded that one of the cells died. It measures 0.2V. The other four are at 3.1-3.2V, which isn’t great but makes sense given that this battery has been sitting for a while.
Removing a cell looks easy, but I haven’t done it since (1) I don’t have a replacement and (2) I need to befriend someone with a spot welder to reconnect the cell.
I’ve heard somewhere that these cells are some kind of high current variant, which seems reasonable.
I could, in theory, solder the cells, but I’m not thrilled about putting that much heat into them. So, I’m shelving this project for now.
Looking around the board for fun, I spotted two unpopulated connectors. The first looks very much like a debug UART. The second like I2C or SPI. I probed the UART header, but there was no data on it. (Which makes sense - you don’t want to use up the stored energy dumping out debug info while idle.)
You may be able to get a different soldering iron that works at a lower temp, enough to de solder the joint but not enough to damage components.
@zleap Based on what I’ve read, it looks like the welds are easy enough to break. My concern is with connecting the new cell - it needs a quality connection which is easy to do with a soldering iron, but that transfers a lot of heat.
I have a Hakko FX-888D and I can adjust the temp over a wide range, so that shouldn’t be a problem.