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).

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. To solve these problems we invented this automotive uninterruptible power supply control module, or car battery backup system. The idea is that you can connect the module to the car’s electrical bus and it will charge an external 12 volt lead acid battery of your choice. Your equipment, which can be a small computer, telemetry equipment, or a car alarm, is connected to the module. This equipment runs off the automobile’s electrical bus until the voltage of the bus drops below a preset voltage, the “N” voltage (from 13.1 to 11.9 volts, depending on your needs). Then the external battery takes over. When the external battery drops below the “P” preset voltage (Between 10 volts and 3 volts depending on your requirements) the power is cut off to either prevent damage to the external battery or to run your equipment as long as possible.