There is now a huge choice of power supplies for every type of vaper. Batteries (Mods) are available with either fixed or replaceable battery cells inside.
Those with fixed internal batteries inside cannot be replaced. When they wear out you will need to replace the whole unit. Other options which enable you to change the internal battery (typically what we call an 18650 cell) give you the freedom to replace just the cell once it wears out.
All of the devices we sell have built-in protection; for safety reasons we do not currently sell mechanical mods.