Thought I'd throw in my pennys worth...
I've purchased three Nico solar
vents in the last 5 years. All of them needed batteries replaced within 18 (eighteen) months.
I think the idea is GREAT the closing vent, bug screens and green water
traps work well - but the cheap
rechargeable batts they use in them aren't worth '*RAP'. Replacing the battery
isn't easy but it's cheaper than throwing the thing out. FYI - non of the replacement batteries have died, so there is a reward for doing the work! The issue is that you are NOT getting what they advertise and while you can certainly get along without the motor
spinning it's not what you paid for.
The vents only have ONE battery
(1.45VDC) so wiring
to 12VDC won't work for very long (but would be entertaining)...