This type with an inbuilt intelligent controller will be better for the longevity of your battery (it operates as a Cetek or equivalent).
I would go for making a connection directly onto the battery via a flying socket in preference to using the Cig lighter if doable.
I have utilised a set up like this to run a 12v LED lighting set up in a friends remote stable about 5 years ago and it's still chuntering away on it's first leisure battery.
Essentials - totally waterproof (not all are) and a controller other than that your choice..
