Discussions

Back up battery at output PWM

Posted by keeyen pang on December 17, 2012 at 7:41am

I read an article from RC helicopter world that recommend to add an additional NIMH 4.8 v battery pack to the receiver to act as insurance against a falling Lipo pack when use BEC from ESC.

Is it a good idea to plug in the 4.8 v battery pack to the APM 2.5 output PWM ? Since there are reports of brownout issue and I think draw power from two difference source will be good.

Thanks

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Bill Bonney December 17, 2012 at 10:19pm

Check the wiki on dual supply for power. It's better to supply the input rails with a separate supply for radio and APM. THe output side and servo will be supplied by the ESCs. If the ESCs cause a brownout the RX and APM will be unaffected.

If you power the same output rail from two supplies there are other considerations like making sure they don't discharge into each other. Like you said keep input and power separate.

If you want redundancy on the power supply to the servos there are other options that switch to a backup supply when power fails on the primary
Stephen R Mann December 17, 2012 at 9:43pm

I bought some 2S batteries and a second BEC, but I haven't tried them in flight. The theory (as I understand the discussion) is that if your main power drops below 9-Volts (on a 3S pack), that the +5V from the ESC drops low enough for the APC to reboot. In the meantime your craft is uncontrolled and likely to crash.