Simple power question

my question refers to these items:

Donkeycar power needs:

  • compute: pi, jetson, neural stick
  • servo: steer
  • throttle: forward motion

Donkeycar power availability:

  • the battery that comes with the RC car
  • Anker battery suggested for basic Donkeycar with pca9685
  • Turnigy battery suggested for better profile energy
  • Inui suggest for Jetson Nano

I really know zero about RC and am putting together RL experiments with these compute devices. So please let me ask silly questions:

  1. let’s say I start with no sombrero. so I am using pca9685 and a raspberry pi. I attach the Anker battery. is this Anker powering all 3 needs listed above (pi, servo, throttle)? or is the original battery that comes with the RC contributing power to the servo throttle and so must be charged and connected?
  2. when I switch to sombreo, I will use the turnigy. I inferred from the video that this battery alone would then be powering all 3 needs. Is this correct?
  3. with Jetson Nano, is the inui also powering all three needs?

a common thread threw all 3 questions, but not the whole question, is whether the original RC battery is needed in these 3 different configurations. I ask because, the related question is:
4. Can I dispense with the original battery that comes with my RC in order to save weight?

I am running this on a 1/16th Short Course Truck from Exceed.

thank you for the help!


Hi Steve, While I could answer your questions one by one you will know little of what I was saying. This is a hardware project just as much as it is a software project. Therefore, just answering the questions, getting more questions and more until it comes down to a 'connect x to y and a to b forever. Instead, I HIGHLY recommend you do a little reading up on the following specific topics and you’ll then know the answers to your questions but better is you will know WHY:

what an RC ESC is, how it is controlled and what the BEC functionality is and how it is used to power things.

What an RC SERVO is and how it is powered and how it is controlled.

What does the PCA9685 do and what is it’s purpose.

What are the signal connections between the rPi and the PCA9685.

How does the raspberry pi get power and how much power does it take( voltage, current, time ).

Hi Steve,

Happy to answer some of these questions.

  1. I have the same setup as you: pca9685 + pi + Anker battery. The Anker battery only powers the Pi via a USB cable, and by extension the pca board which takes power from the Pi via pins on the GPIO.

Throttle + Servo is powered by the RC battery. These batteries provide significantly more power and a higher voltage than a USB cable can.

2 and 3: It’s still the same situation. Sombrero will power the Pi and therefore you don’t need to have a battery plugged in to the Pi directly. In all cases the RC motor will simply draw too much power for a battery designed to run small electronic devices like the Pi, Nano, etc.

In short, no you still need a decent RC battery in your car.