Dimensions fit Heavy Duty Modular Fuse Box Series (BF43x) and Battery Switch, compatible with mainstream products on the market. Once your main starter battery is sufficiently charged, it will begin charging the second battery as well. Surface or panel mount options provide flexibility during installation. No voltage drops compared to battery isolator diodes (0.6V). Features a durable glass fiber reinforced nylon shell. Specifications: Condition: New Material: Nylon Color: Black Size: 7 x 7 x 6 cm / 2.8 x 2.8 x 2.4 in Nominal Voltage: DC 12V Combine / Open Voltage: DC 13.3V / 12.8V Continuous Current Rating: 125A Intermittent Current Rating: 140A Power Consumption: 10mA (Standby) / 330mA (Engage) / 0mA (Storage Mode) Certification: CE, IP67 Package Weight: Approx. 234g Functional Features: After the engine stalls, the house battery discharges to the connected load device, and the VSR disconnects when the battery voltage drops below 12.8V. The starter battery remains isolated and does not discharge to the load. When the house battery is depleted or not charging, the starter battery retains sufficient charge to start the engine. Packing List: 1 x Voltage Sensitive Relay (VSR) 4 x Screws 1 x Manual