Put a wing nut terminal on the negative side and it is easy to disconnect.
Also the SolarPulse line from PulseTech are great desulfating chargers at a reasonable price. They're a great way to keep a car's battery good when you can't connect it to a plugin.
I have one of their 3 watt systems on the roof of my trailer to keep the battery of whatever car is inside topped off. And when storing the trailer it keeps the trailer brake battery good.