I am curious to know what others think about this topic. Is it best to power everything from one battery, or to have a separate battery for auxiliary systems such as position lighting and camera gimbal?
It seems intuitive to me that the latter approach is preferable for at least two reasons:
I don’t want auxiliary loads draining my flight battery.
I don’t want the auxiliary loads to interfere with proper measurement of remaining flight battery capacity. To clarify this point a bit - the position lighting driver I am working on generates significant current spikes as I flash several one watt LEDs twice a second. (Blink blink pause, blink blink pause, repeat).
My conclusion could indeed be wrong, which is why I am raising the question here.
If you’re interested in big drones (like 12s or so on), I really recommend you to isolate your flight control systems from propulsion system. Auxiliary loads draining your battery is the last thing you should worry about. There is really much more interference than you can think about. I think ardupilot’s current measuring frequency is higher than you blinking leds so there won’t be any problems unless you are blinking really fast many leds. But in short using a second battery is not a bad idea at all.
While I am only flying 3S batteries at the moment on an F550, I believe the concerns are real in that realm. I have achieved 18 minute flights with a 10000 mAh 25C 3S battery using what I believe to be a fairly conservative strategy of RTL around 20% capacity remaining.
My circuit attempts to flash LEDs at high current for very short pulses in the neighborhood of 20 milliseconds which I don’t expect to be reliably detected by the FC. I am using one watt LEDs that are painful to look at when the pulses are at rated current. The possibility exists to drive them at significantly higher current for daytime use due to the low duty cycle. That is one reason driving my preference for a separate battery. I have also recognized that a night mode might be appropriate where the LEDs are driven with less current.
Ok, so you have a low voltage system on your drone.
But from what I understand, you have a high current flowing through the wires.
Please place them on the drone as far as possible from the flight controller (especially the GPS module that contains the magnetometer) or place the GPS module above the wires’ level.
A separate battery for your payload is a good idea for your work.