12V vs 24V Battery System
I am looking for direction regarding a 12V vs 24V off grid electrical system, from the point of view of MPPT charge controller. Pertinent system info:
- 1KW PV with single charge MPPT controller
- Four Interstate GC2 6V, 210 AH golf cart batteries
- 150’ distance between PV and controller
- Using 12V loads wherever possible with multiple 12V power points wired throughout the cabin, short runs (~30’) to each power point from central 12V power distribution.
- the PV controller and inverter are <10’ from the batteries
- the location is Maine, where cloudy days are common
My options are to wire the batteries as 12V, and distribute power directly, or 24V and step down to 12V either at the center of the 12V distribution or use smaller converters at each 12V power point.
I am leaning towards using three 290W to 330W 20V or 24V solar panels in series with a MidNite Solar Classic 200 Controller. The Midnite Solar controller sizing tool has a note stating that higher input voltage on MPPT controllers are less efficient. I want a higher voltage so I can use a reasonable gauge wire over the 150’ from PV to controller.
Will I see significant controller power loss in a 12V system with a 100V – 120V input voltage?
Will this higher voltage help for low light days?
I would consider using 4 panels in a 2 string configuration to feed a 12V battery bank
1.2KW off grid system; 2 strings of 2ea 305W 60 cell panels on a redneck ground mount; MNPV3 combiner feeds a MN Classic 150 located 100' away; 12V 460AH FLA battery bank powers a cabin-wide 12V DC system as well as a Cotek 700W PSW inverter; Honda EU2000i and IOTA 55A charger bridge cloudy days and a Champion 3800W generator for short duration, power hungry appliances.