I have a Ctek one I got from Costco! That has done me proud for a number of years not only trickle charges the battery as needed (monitors level of charge) it can condition the battery too! I also have one as part of the car coon storage system and that is fine but not as good as the Ctek one but it will keep the bubble up if the power goes using the car battery then recharge it afterwards! - These can both be left connected to the battery indefinately.

These charges keep the battery in good condition but take a long time to charge the battery. - fast chargers aren't so kind to the battery but will get you going in several 10s of minutes!