Hello
(1) Most cordless tools use the 18650 battery in there battery pack.
12 volts battery pack have three 18650 battery in pack when replacing the battery ,do person buy battery with out circuits protection in the battery.
Do cordless tools battery have protection build in for each individual battery in the pack ?
Don't know what kind battery to get with circuit protection build in the battery or no circuit protection.
(2) when looking at e Bay on the 18650 battery ,there so many different ampere hour listed for the 18650 battery ,is there way testing to find how true the ampere hour list on the battery.
mrel

 

Most batteries don't use cell-level protection, they use a BMS in the battery (or occasionally in the tool).

It is much better to replace all cells in the pack instead of only some. The capacity (AH) of the cells should be as high as you can afford, and you should probably use high discharge capable cells.

 

The high capacity claims of some of the eBay batteries is nonsence. Iirc anything above 3500mah is suspect. Buy from a battery seller that only sells batteries. A lot of them sell batteries for vaping devices and have good feedback from users.