The 1318 and 1319 are 100A battery separator modules with an integrated relay for 28V systems—the 1318 is unidirectional and the 1319 is bidirectional. The 1318 monitors only the main battery and charges the auxiliary battery if the main battery is above the connect threshold. The 1319 monitors both the main and auxiliary battery banks. If either battery bank is above the connect threshold, the relay connects the two banks together. If the batteries are below the disconnect threshold, the unit will open the relay. The connect threshold is set to a nominal voltage of 26.8V, which would only be reached when the charging system is operational. This will cause the relay to only close when the charging system is operational, charging both banks of batteries. The disconnect voltage is set to a nominal 25.7V, which is near the full charge resting voltage of the batteries. This will cause the relay to be opened shortly after the engine is stopped, attempting to preserve 100% of the starting battery capacity for engine cranking.