Backup/Redundant batteries
We recently had an interesting discussion on the NSRCA pattern list concerning backup batteries. The power supply is the first thing we think of when we have trouble so it would be nice to eliminate it as a source of catastrophic failure. I don’t know who should get credit for the concept but I got interested when Chris Moon suggested making up a special voltage regulator that would connect to the balance connector of the motor pack, tapping off the bottom two cells. I suggested just making a simple cable that could be connected to any voltage regulator and these are now available from F3A Unlimited.
The way I configured my system was to build a simplified version of my Perfect Switch Harness that would allow me to connect an onboard voltmeter so I could read the voltage of the two cells when I installed the motor battery. This would assure me I had installed a charged battery. I have been carrying around an Eagle Tree data logger and display to provide this info. You only need to take off once with a perfectly good but discharged battery and come down with a bad battery, to wish you had been more careful. I set the output of this regulator to 6.3 volts so the system would not draw current from my receiver pack which is regulated to 6.0 volts. I then charged my receiver pack to the storage voltage and haven’t charged it since.
Then one of the guys at the field says how do you know you aren’t using up the capacity of the receiver pack so I went home and installed a voltmeter that would read both. The photo shows the results.
Jim O