I have now set up my battery charger power supply unit with a cable long enough to supply power for my small quad copter for inside testing. This will save the life of the batteries as well avoid the hassle of swapping them over constantly for when doing PID tuning etc. Only thing its not powerful enough to fly my X8 quad and trips the over load at about 29amps. Ill try see if ii will run my hex next. Here is the video of the small quad run


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  • The unit I have is just a cheap 12v PSU that I use to power my Battery charger. I tested it on my hex and its just not quite enough voltage to get it off the ground. The voltage reading on Mission Planner while its running is about 11.5 to 11.85 volts so the drop in voltage is not a lot.The max amps gets up to around 35 to 38amps.

     Hawhoo, not a bad idea except part the reason I wanted this is to help preserve my lipos battery life.

  • how about just keeping the battery in place and using it as a buffer?

  • What about feeding ac directly to a light weight (if there is such a thing) switching power supply on the multicopter?

  • Developer

    Very interesting.  In Japan we have a requirement to provide 100 hours of flight records (for professional UAVs).  Now those need to be with a complete set-up including battery but I've been thinking that a similar set-up to what you have would be useful for long term testing to see what tends to break first (escs, autopilot, motors, prop mounts, etc).  thanks for the info on issues that would likely come up.

  • Did a very similar setup for my quad. Connected the quad to an adjustable voltage power supply. Quad drew around 12v without a payload and upto 17v with a 2.5lb payload. Like others noted, I initially had problems with voltage drops over my 5 meter 12aug wire. To solve this, I installed capacitors along the wire. This took care of the problem.

  • Ellison, no, most chargers aren't even close for a number of reasons. Typical quad is 4 each 850kv motor drawing at least 10 amps each on a typical 3 cell 11.1V setup. The charger says 12 volts, but since it's a linear supply with a huge 60hz transformer, it's no where near 12volts except fully loaded down. This means open circuit voltage could be as high as 18-20 volts and loaded voltages drops until saturation. They are rated for 6-10 amps continuous and can probably supply 15-20 intermittent. The 50amp starting rating on some is no where near continuous and oh by the way, the same rectifier diodes are used so how long do they last at those currents?


    Bad power output from dual half wave rectifier and no filter cap

    Not enough current

    Horrible voltage regulation


    If you just want to burn up your electronics and not fly, by all means go for it. Even the switcher ones are designed to charge a battery. With no battery attached, they often won't output anything.

  • Point of advice from someone working with a  UAV powered from a power supply for initial indoor trial runs:

    The cables have minimal resistance to dc current, BUT for current with sinusoidal harmonics their 'complex resistance' is proportional to impedance times the frequency.

    The ESCs work in a switching way, @ high frequencies (8 kHz,16 kHz etc) so unfortunately 'composite resistance' manifests itself in a significant voltage drop along the cable

    You can notice this if you check the voltage that actually arrives at the copter with a Multimeter while it is operating at the Throttle values you use for hover. While the PSU keeps 12V at its output, because of the aforementioned voltage drop along the wires you should notice a voltage much lower than 12V at the copter side. 

    And it's not an issue of how powerful your PSU is, because it will always output 12V, the amperage will only differ.

    So all in all longer wires means larger voltage drop.  But you can't actually work with short ones either. So if you really want to try this approach you will probably need an adjustable voltage psu which are kind of costly, if you also want to go high in amperage.

    Additionally to that, yes, the cables have a dampening effect on the copter's response. Also if you manage to fly one of your copters (a lightweight one) at a lower arriving voltage (say 10.5 Volts), be aware that your PID params won't be reliable because the ESCs (actually the combination ESC+Motor+Propeller) have significantly different responses at different voltages. 

    Hope I added info which will be of some use 2 u

  • I tried that when I first started out, with a PC power supply for my quad.  Not nearly enough power.  What kind of battery charger power supply are you using?  I think a car battery charger/starter would have enough juice to run any multicopter.  

  • Moderator
    So switch to a p/s with higher output.

    Do you not think the weight of the cord will affect the PIDS?
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