I have a size 27 deep cycle battery on my popup. I have pulled the fuse out so that no current is going to the camper while it's not being used. I have been putting the battery on a 2 amp charger about once a month until it is fully charged and then I take the charger off. Is this sufficient in keeping the battery in good condition? I know that a "battery tender" would be better, but at this time I can't afford to purchase one.