You haven't specified which model and there are different models within every manufacturer's line of chargers. That said, any maintainer only has to replace what may have leaked down, perhaps while in storage. Only very low currents are required to "trickle" charge as maintenance. A low current model will likely still be able to charge a depleted battery, but it may take a considerable time (days?). I have installed a similarly priced CTEK Muti US3300 that maxes out at 3.3 amps, but has been quite adequate for maintaining my trailer queen's pair of deep cycle Group 27H batteries. I don't have a complex 2-bank charging circuit though. I just move a selector switch between batteries on a regular basis, keeping one fresh battery always in reserve for piece of mind. - Grandad