18650 notes

I found a very useful diagram that I am posting here to do with the 3 different sizes of '18650' cells. The 18 is the diameter in mm, the 65 is the length except it isn't always. There are two kinds of normal (unprotected) cells, flat top which is 65mm long, and one with a button or pointy top that is 67mm long. What you most likely should be buying are the button or pointy type with a 'protection PCB' inside, it is 69mm long. That 'protection PCB' is actually one of several possibilities. Just know that the cell is protected from SOME bad events. If you need to use a 18650 in a situation or environment that could affect human (or doggie) health up to and including death, then do your research and deal with it properly. I use proper chargers, have a steel box lined with fire proof material, vented etc etc plus a fireproof bag in a fireproof bag while charging the big boys.

I have never had a problem with the 18650, but an ANKER power brick did swell up on me and it had not been used, or charged in months. That is about like having your Rolls Royce break down, it just doesn't happen.