Depends on the brand. Some (VUSE) are proprietary, won't fit in anything else and, with their microchip, wouldn't work in something else even if they did fit. Some (MarkTEN) use standardized connectors like 510/302/808/etc.. Yet others use something almost-but-not-quite-like a standard. For example, BLU uses a standard 510 connector but with reversed polarity (so you don't ever want to put a BLU battery on another charger, or vice versa, even though it will
fit just fine) and Green Smoke use a modified KR808D such that their carts will fit on other
batteries, but their batteries won't fit other brand's carts (I think, or maybe it's the other way around.)