The below schematic is for our EPEVER Dual Battery Solar Charge Controller
It is important that ALL the batteries are at the same voltage and the “MAIN” Battery is same amps AH (if they are different sizes/AH and Ages then it is not generally recommended see further info).
The boat/van starter battery, will likely be just one battery @ 12 volts – with this controller, it will be trickle charged at 1 amp.
However, the starter battery can be at 24volts – in which case the “MAIN” battery must also be at 24volts. These batteries would need to be connected in series
Most boats and vans will be at 12 volts. If the “MAIN” Battery has more than one battery connected together, then the two or more batteries should be be in parallel – that is +ve to +ve and -ve to -ve. Although, this is not always the case.
Solar Panels / Arrays
For this controller it is better that the Solar Panels are connected in Parallel as the batteries. +ve to +ve and -ve to -ve.. It will work better when shaded.
Boat Safety Scheme
It is mandatory for the BSS to have all electrical circuits isolated using a DC Isolator. Also, recommended practice in vans (breaker in Diag.).