I understand the requirement. There are two approaches. One measures voltage, and when it goes below a threshold begins shutdown, and when it goes below a final threshold it disconnects the load.
The second approach is a charge controller, which estimates the capacity of the battery bank by measuring the power input to the bank against the power output. When the estimated capacity drops below a threshold, the shutdown is begun. It is possible to use both approaches. Each has advantages and disadvantages. I don't know of any ready-made examples. If I were using an Arduino, then I would need: - measured proof that the USB ground is the same as the power supply input ground, - a USB Arduino, such as the Uno, - one spare USB port, to connect the Arduino to, - a 10k trimpot, as a voltage divider, dividing the 0V to 15V input signal down to the 0 to 5V range, - a sense cable from the trimpot to the battery bank (because if the computer 12V input is used, the resistance of the wiring between the battery bank and the computer would affect the result), - software on the Arduino, which reads the voltage and sends it to the computer, (roughly half an hour of work for an Arduino expert, roughly two hours for a non-expert), - software on the computer that reads voltage, averages several samples, and shuts down. A wasteful alternative would be a UPS with no load, with the power down signal cable of the UPS connected to the 12V DC computer. -- James Cameron http://quozl.linux.org.au/ _______________________________________________ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
