A weekend will run down batteries in no time depending on what charge system you have, or even what the ambient tempreture may be. We tried a couple of chargers and found the CTEK to be pretty bullet proof, for doing the job, surviving rugged travel, and getting the job done either when mounted in the camper trailer, or just sitting on charge while in the garage.
if you can find a power point, or use a generator, you're back in the game with a battery charger. Simply hook up the Negative & Positive clamps respectively to your batteries, and turn the charger on. It's best practice to keep batteries full and topped up when not in use.
Depending on the quality of the product you choose, some products can be mounted directly to your car or camper trailer and hard wired. Then you can just run a power cable to the charger and you're topping up again. Alternatively you may keep the charger at home in the garage. We take ours everywhere and has been a lifesaver with the use of a generator when there are no facillities available.
Do your research when considering what's right for you, also consider the size of your batteries first before purchasing a charger. Ensure the AMP rating is up to the job or you might find yourself having to buy another one. (like we did)Talk to a battery reseller, that's what they are good at, so get it right the first time.