Wife is new owner of xb 502 and I am concerned about damaging batteries. I have been through this with the boat and motorhome. What inexpensive 3 stage charger would you recommend? It is a combined 48 volts 12AH. Would one of those 20 dollar maintainers suffice? I would like to be able to charge it overnight or even for 24 hours without damaging it. Thanks in advance.