Cars DC UPS 12 Volt Power Supply

Automotive battery backup system. 12 volt DC UPS module keeps 12 volt equipment alive in cars and taxis using an external sealed lead acid battery and acts as a battery back-up (BBU).
Click here for 5 amp version with status output
Click here for the 12 amp version.
Click here for the 24V 12A car UPS controller
Complete vehicle UPS with control module and 1.2AH lead acid battery
AC input 6V, 12V, 24V, 48V battery backup power supplies
This little gadget solves several problems for electronics in cars.
First it allows you to charge an external lead acid battery from the car's electrical bus.
Second it isolates the extra battery from the car so it won't be discharged by the car electronics, and it won't try to participate in starting the car.
Third it powers your equipment in the car using the car electrical system, but switches to external battery power when the car's battery is stolen, or drops below a predetermined voltage.
Fourth, it prevents the external battery from being over-discharged, keeping it from being damaged.
Fifth, it prevents your equipment from running the car's battery down so the car can't be started. In one configuration it cuts off the car's battery when the voltage gets below 13.1 volts, then switches over to the external battery, in other words it switches over to the auxiliary battery when the engine is shut off and the alternator stops.
In another configuration the crossover voltage is lower, say 12.0 volts. This allows your equipment to run off the car's battery but cut off while the car's main battery still has enough power to safely start the engine.