I suggest a tiny 1-way valve that allows air to flow out of the battery, to activate a pressure switch, but which is normally closed.
It could be as simple as a domed silicone flap, or it could be, for example, in the shape of a three or four sided pyramid, with the edges cut and the bottom open.
I know the hole in the battery connector is extremely small and this may not be a feasible suggestion, but I thought I would throw it out there since eliquid in auto batteries is such a common problem, and probably the main drawback of using an auto battery (some of the others being the auto cutoff and need for a certain strength of draw to switch on the voltage)
It could be as simple as a domed silicone flap, or it could be, for example, in the shape of a three or four sided pyramid, with the edges cut and the bottom open.
I know the hole in the battery connector is extremely small and this may not be a feasible suggestion, but I thought I would throw it out there since eliquid in auto batteries is such a common problem, and probably the main drawback of using an auto battery (some of the others being the auto cutoff and need for a certain strength of draw to switch on the voltage)
