Redundant Receiver Battery Packs

Redundant Receiver Battery Packs

RC battery packs

NOTE: The batteries can be of different capacities. For example, you could run one 500 mAh pack and a 1200 mAh pack with no adverse affects.  DO NOT use packs that have different cell counts. In other words DO NOT use a 4 cell pack with a 5 cell pack!

To test your packs, just turn on the first switch, check for proper operation, turn off the switch, turn on the second switch, check for proper operation, turn on both switches and go flying.

NOTE:  If you don't want to carry the additional weight of a second battery pack, but would like some redundancy, just solder another wire onto your battery pack and run a single battery with two switch harnesses. Switch harnesses are much more likely to fail from vibration than batteries anyway....

Additional explanation from Red Scholefield:

Discharging Ni-Cd packs (having the same number of cells) in parallel is not a problem and is a good way to increase your flying time. They do not even have to be the same capacity. Think about it, the discharge voltage of a Ni-Cd starts at 1.31 volts while the charge voltage is greater than 1.31 so there is no way one pack can charge another. Charging packs in parallel is another story as this can lead to problems. One pack can "hog" the charge current leaving the other pack only partially charged. I have run experiments in parallel charging and have not found it to be as big a problem as thought however. In large, expensive show planes the use of redundant packs is a good practice. These should be run through their own switch harness and into a spare channel on the receiver. If you use 5 cell packs you could even throw in a diode to isolate the two systems on the off chance that one pack should short out (probability very, very low - I have never seen a cell short in use -- only when resting).

Red S.
+ Red's R/C Battery Clinic -
Specializing in R/C Battery Systems

Andrew, 30/06:
Excellent explanation thanks

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