most of these I have seen have the charge protection tabs on the top. are the laptop batteries different?
most of my experience is from buying fresh cells to use as caving headlamp batteries back in the day.
most of my experience is from buying fresh cells to use as caving headlamp batteries back in the day.
That depends on the cell.
Some cells have charge protection. Others don't. The 18650 cell is standardized only in size-and-shape. The actual protection, chemicals, and other specifications are completely different from cell to cell.
Heck, some 18650s have 3.2V nominal voltage, while others have 3.7V.
IIRC, charge protection causes a voltage drop. So some applications prefer to use unprotected cells (with the overall device implementing charge protection elsewhere). For example, Laptops probably have ONE charge-protection circuit somewhere in their construction, rather than 6-charge protection circuits (each cell). This simple fix will cause 1/6th the voltage drop compared to 6x individual charge protection circuits.
(Some) manufacturers provide specs for their batteries, but most of them are coming from no-name factories in China with no reputation at stake, so there's either nothing published or it's exaggerated.