Portable power source for Raspberry pi and associated peripherals and sensors

Soumen Roy
Soumen Roy used Ask the Experts™
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Hello experts,

I have a Raspberry Pi 3B running with a Pi No IR Camera(with two infrared light sources as comes in the No IR Camera package), and a handful of sensors working on the GPIO Pins. The setup is to be mounted on a base provided with four wheels and two DC motors.. As of now, the Pi and its attachments run from the power socket. However, once it is mounted on the robot base, I will need some kind of portable power source.. Please suggest something that can run the setup for 12 hours at a stretch at least.

I know the question might be vague, please ask for the details that will be needed, and I will provide them..

Thanks in advance..
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Principal Software Engineer
Commented:
The Pi 3B requires 1.2 amps of 5V = 6 watts.  (Figure using the maximum power rather than the "typical" power so that you don't need to redesign later.)

Figure double that to run the camera and two small DC motors (2.4A).  This is a guess and it assumes very small motors which are always in operation.  Bigger motors will require more power and the calculations below would have to be refigured.

The setup will require around 3.6A of 5V, or 18 watts.

18 watts is not a lot of power but over a period of 12 hours it's 216 watt-hours.  The only really convenient portable power source for that kind of power is a sealed lead-acid (SLA) battery.  If you choose a 12V battery then you can use 12V motors, which are easier to find than 5V motors.

18 watts at 12 volts is 1.5 amps.  Over 12 hours, the required battery capacity is 18 amp-hours.  These batteries are readily available on fleabay or at local battery stores.

Then use a DC-DC converter (also readily available on fleabay) to convert the 12V to 5V for the Pi and its 5V peripherals.

You'll need snubbers across the DC motors or chokes inline to prevent inductive kickbacks (caused by commutation) from going back up the power lines to other devices.
Soumen RoySenior Manager

Author

Commented:
@Dr. Klahn, thank you for the suggestion.. Actually, there was a major gap in my question from what the project is actually meant for..

12 hours would only be the testing part. Suppose, I have to leave my house for a vacation of 2 weeks or more.. Is there any reliable power source for keeping the setup alive for such prolonged periods?
Dr. KlahnPrincipal Software Engineer

Commented:
The proposed gadget will require 432 watt-hours per day.  Times two weeks = 6,048 watt-hours.

A good quality car battery has a capacity around 100 amp-hours, times 12 volts = 1,200 watt-hours.

The gadget would have to carry around 5 full size car batteries.   This is probably not practical.

There are higher power densities from lithium batteries, but they have a tendency to explode that is not desirable in an application where nobody will see the fire.

Perhaps have the gadget periodically return to base and charge up the battery?
Soumen RoySenior Manager

Author

Commented:
That is an option of course, I shall look into it..

Someone suggested me to use smaller, less power consuming controllers if possible.. I will be looking for such alternatives when I get the time..
Soumen RoySenior Manager

Author

Commented:
Thank you for your suggestion

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