Powering Your Robot
There are two main schools of thought when it
comes to powering small robots. Regardless of which
school you go with, do NOT use alkaline batteries.
Your robot will go through a fresh set of batteries in
less than 15 minutes! Use NimH, NiCd, LiPo, LiOn,
etc., rechargeable batteries — their power curves are
a much better match for the power usage of motors.
1) “One for All” — Use One Battery to Power
I can see the attraction of trying to use only one
• Fewer batteries to carry
• Lower cost
• Easy to “brown out” (reset) the Raspberry Pi
• Shorter run time for the robot
• Cost of a BEC (battery eliminator circuit)
If you wish to use just a single battery pack, do
yourself a favor and minimize the disadvantages:
• Use a 7.4V NiCd or LiPo RC battery pack with 5,000
mAh or higher capacity
• Use a BEC to provide regulated power for the
Raspberry Pi and electronics
Do NOT skimp on the BEC. If your Pi browns out when
the motors stall, you stand a good chance of corrupting the
boot SD card in the Pi.
Check out these BEC links:
2) “Multiple Power Sources” — Use Two (or more)
Separate Power Supplies
I prefer to avoid the need for a BEC/UBEC, and have
separate power supplies for the electronics and the motors.
• 5V 2A USB power bank for driving the electronics
• 4.8V- 7.4V Battery pack for the motors
Some people prefer to have even more battery packs,
such as for:
• Separate servo and DC motor power supplies
• Backup electronics battery
Personally, I don’t think there is a need for more than
two power systems in a relatively simple robot.
• Avoids brown outs due to excessive power drain
• Longer run time for the robot
• Possibly somewhat higher cost (cost of BEC vs. USB
• More batteries on the robot
In my case, on my Elf robot I use a 5,200 mAh USB
power bank which runs the electronics (including Wi-Fi) for
more than four hours, along with a 4x AA NimH battery
pack for the motors.
Serving Raspberry Pi
By William Henning
54 SERVO 05.2016
In the last column, I took a look at some
of the sensors you would want to use on
your robot. Now, we can decide on the
power source(s) for your robot and
assemble your Raspberry Pi bot!
Hobbit with battery packs.