Cosmo

You definitely need more than a standard trickle charger, otherwise you will damage your battery if left on charge for long periods. I have a Draper 12V Intelligent Battery Charger which continually monitors the amount of charge required and can be left connected for long periods. It also handles gel cell batteries. It wasn't that much more expensive than a standard charger and will probably repay itself in just a years worth of extra battery life.