Onboard Charging Question

[jdk426]

Hi guys new to the board. Figured id throw my question out here and possibly someone can help. I am new to fishing/boating etc but tryingto soak up as much info as i can. My question is here. I have 2 12v's running together creating a 24v for my trolling motor alone. I have a cranking battery that does just that and has bilge pump and running lights etc. Just a few gadgets on the cranking motor. Ok i plan to install a onboard charger this weekend. So my plan is to get a 3 bank charger. Now it wont hurt to hook up 1 bank to each trolling motor battery equaling 2 banks and 1 to my cranking battery correct? I just dont want to effect any of the batteries in any way. Just making sure im on the right track here. My other question is when i do goto hook it up. Like on the 24v connection for the trolling motor its + to - . But on the onboard charger i would hook up pos and neg to one battery then the same for the next not crossing them right. I guess to make it simple it would be like connecting Pos plus Neg to my cranking battery. I wouldnt cross the + and - on the 2 12v's that are running the trolling motor if that makes much sense. Im trying to keep it simple but i guess im confusing myself lol. Anyways fellas hope you can understand what im trying to get at here. Thanks Jerry