Jay.
Club Member
Sounds like that would drain the battery tooI wouldn't use one of those just to keep the clock running though, there not good for the battery long term. If you really need to have the correct time, all the time and want to keep the cut off switch (which i would definitely recommend keeping) you could wire just the clock directly to the battery no?
Newer 'smart' trickle chargers like the Ctek are quite advanced and have been proven not to be detrimental to your battery health - I'd keep the car on that if you have access to a power source