Basically, a voltage sensing relay will produce a good outcome for healthy battery banks but isolates batteries that fall below about 11.5V. A clever product.
Specifications: • Continuous rating: 140A • Cut in voltage: 13.7VDC • Cut off voltage: 12.8V • Dimensions: 67(L) x 67(W) x 53(H)mm
See MB3880 for a wiring kit version