If you don’t like to power down your Heli at every battery change, and losing your GPS fix... there is a solution.

Just install a parallel second battery connecter (can be a much smaller one), prepare an old battery with the matching connector and a Diode in the + wire as a backup battery.

(To charge the backup battery you have connect the charger behind the diode)


Before changing the main battery connect the backup to the 2.connecter, change the battery, disconnect the backup and go flying again without loss of GPS fix and so forth.


By the way I had a very successful first flight with my T-Rex450 Pro and APM2

in stabilize mode. Very stable Tail and Hover, unfortunately the weather turned bad I had to stop.

Will keep you posted.

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  • @RL
    Of course regarding ESC behaviour, so why would booting APM from power Lipo cause spin Up? Is this a bug?
  • Crasher, any good ESC will not spin up if it receives a high signal when it is powered up.  I have the cheapest of the cheap ESC in a little foam airplane, and it just beeps if it gets a signal when you plug it in.  

    As for my statement that I thought you consider the battery powering your aircraft the least important, it's just based on the fact that you have all these other batteries, but you didn't like the idea of adding one more.  It's not a big deal.  I totally get your point that with multicopters, adding an extra battery doesn't really buy you much.  But every other vehicle, I think it will.

  • @RL
    Once again I cannot see your point. Two seperate batteries may prevent a spin up while APM is booting, but doesn't prevent a potential spin up when you plug the power lipo in? You could still get a spin-up.

    As I said, the point of redundant systems is to minimise the impact of a failure, or reduce the liklihood of a failure. Two seperate batteries with one powering APM actually doubles the liklihood of a critical failure.
  • All my GPS guided vehicles had standby power connectors.  It's about time standby power got more attention.  Another use is keeping the vehicle always powered up on AC, so it can take off at any time, with a full satellite count.  The supercaps for retaining ephemeris on those GPS modules never gave the instant accuracy of standby power.

  • @RL rhis does not explain your earlier negative comment that i consider the battery powering my aircraft the least important? Please explain??
  • I guess it depends on the aircraft.  If you have a multi-copter, yes, any sort of main power failure means you crash.  But if you have an airplane or helicopter, both can survive a main power failure, if you can control them.

    And in all cases, even multi-copters, having a separate power supply for the APM is safer, as it's easy to power up and let the APM boot with zero risk of having the motors spin up unintentionally, since you can just leave them disconnected until you're ready to go.

  • Sorry I missed to mention that I put 5x a 1amp diodes in series to have a voltage drop from about 3.5Volt. The discharge voltage of a 3s is about 10V, the fully charged backup Battery is about 12.6V, so 12.6 – 3.5 = 9.1V.

    This prevents a charge current to the discharged main battery.

    Or if you don’t like the stack of diodes and go the saver way, use a 6sNiMh (~7V) as backup and 1 diode.

    In my case it works.

  • @RL
    Respectfully i think your think is flawed:
    Scenario 1: your mini lipo fails in som way = crash
    Scenario 2: your main lipo fails in some way = crash

    You have introduced a second failure point that offers no real redundancy. It cannot power servos or the drive motors, it cannot power the servos, so what have you realistically prevented?

    On my systems I have a massively over powered 5V supply which is very stable, ripple free and has redundancy (two systems in parallel). If my main battery fails, i crash, but so would your solution, if one of my UBECs fails, i survive. But Lipos fail, so if you mismanage yours charge wise (forget to charge it) or the lipo/lead/connector fails you will crash.

    I hope you can see my thinking..
  • @Crasher, so all those batteries, and the least important battery to you is the one actually flying the aircraft?

  • Forgot to mention, 2 sec to get 3d fix hot start!  much better now :)

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