Review on Power Off Protection Module 12V Controller by Daniel Ton

This device does not draw current and does not charge the battery terminals. The battery is isolated by the relay until the primary input fails. The relay will not switch to battery until the primary DC+ input drops below 2 volts. The relay is energized and the LED lights up when the DC+ input is powered and consuming 0.55W. The relay/LED does not consume battery power when the DC+ input is zero. The board has a regulator to keep the relay coil at 12 volts over the full input voltage range. I use this relay to secure the GPS tracker in my trailer. The power input is connected to the trailer battery, the battery input (backup) is connected to 8 D-cell batteries. D-cell batteries keep the GPS tracker running if someone disconnects the trailer battery.