I'm looking at how to replace the neglected LA batteries in a bass boat with LFP. Currently it has a 12v starting battery that also drives all of the small loads like pumps, depthfinder etc. Then it has two completely separate deep cycle's that both run up to the trolling motor to give it two 12 volt inputs. Presumably this is to allow the use of either 12 or 24 volt motors, but it was a new one for me. Further investigation is needed to understand how the existing 24V motor actually uses these two inputs. I am fairly certain there's no charging of any kind other than shore power, so I think no need to worry about isolating an overvoltage BMS disconnect in the design.
The drop in solution is to build or buy 3 marine grade LFP batteries and connect them into the same configuration as the current LA's - and I think it would work great. But it's not particularly elegant or wallet friendly and I was wondering if it's advisable to size the batteries to create a hybrid. So instead of three 100Ah batteries get something like a 200Ah "Main" for starter/trolling plus a 100Ah "booster" exclusively for trolling.
It seems unconventional to connect two different capacities like this to create a hybrid 12/24v system, but it would save money and I think would be a superior system. The main battery could get a top of the line BMS with capacity monitoring while the booster can receive whatever cheap BMS fits the load requirements. The start current would be cut in half from a C-rate perspective. The main battery would have more capacity if it experienced abnormal loads. The capacity ratio of the two batteries could be adjusted based on expected usage rates. And the wiring wouldn't change a bit except to connect two loads to the main battery.
Is there any reason this is a bad idea?
The drop in solution is to build or buy 3 marine grade LFP batteries and connect them into the same configuration as the current LA's - and I think it would work great. But it's not particularly elegant or wallet friendly and I was wondering if it's advisable to size the batteries to create a hybrid. So instead of three 100Ah batteries get something like a 200Ah "Main" for starter/trolling plus a 100Ah "booster" exclusively for trolling.
It seems unconventional to connect two different capacities like this to create a hybrid 12/24v system, but it would save money and I think would be a superior system. The main battery could get a top of the line BMS with capacity monitoring while the booster can receive whatever cheap BMS fits the load requirements. The start current would be cut in half from a C-rate perspective. The main battery would have more capacity if it experienced abnormal loads. The capacity ratio of the two batteries could be adjusted based on expected usage rates. And the wiring wouldn't change a bit except to connect two loads to the main battery.
Is there any reason this is a bad idea?
