The BB1248120 is able to charge in both directions – from the vehicle battery to the house battery bank as well as from the house battery bank back to the vehicle battery. As long as the house battery bank is over 13.2V (13.5V if lithium) and the vehicle battery is below 13V the battery to battery charger will allow approximately half current (~20A) to flow back to the vehicle battery up to about 13.4V (float voltage). This unique feature allows the vehicle/starter battery to remain topped up when there is surplus energy in the house battery bank. Best of all, this feature will NOT drain your house battery bank. Instead, it only uses surplus power. Once your alternator / engine turns the unit will revert to normal charging of the hosue battery bank. This mode can be disabled, but is on as default.

Self recovering protections:

1. Under voltage protection
2. Input over voltage protection
3. Output over voltage protection
4. Over current protection
5. Charge over temperature

Other specifications:

Operational temperature: -20 deg C -> 60 deg C
Cooling method: thermostatically controlled
Fan: variable low speed
Dimensions: 10.6″ x 5.1″ x 2.9″ (270mm x 130mm x 73mm)
Weight: 4lbs (1.8Kg)
Optional Remote control available