My boat has a 12 volt trolling motor and the battery(1) does not last long in wind. If I install a second 12 volt battery and connect them in parallel, positive to positive and negative to negative, is there any advantage to having a cutoff switch between them and only using the first one until it gets weak? Is it better to use the current from both at the same time? I do not have any experience in this area. Thanks for any information!