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Exploring alternate methods for providing DC power to Raspberry Pi

colporteur

I'm in need of a battery power solution for a Raspberry Pi?

My plan was to use a 5VDC lithium-ion battery connected via the USB micro connector to power the Pi. I have had to rethink this because of extreme space limitations. The power connector on the Pi makes it a difficult fit in the space that I am using.

My next thought was to connect the battery directly to the 5V and GND pins. I seem to recall that this could be used on Pi's. I then stumbled across an article that suggested, if this method is used, the circuit would require a Universal Battery Eliminator Circuit (UBEC). I have no voltage level issues. The battery supply is 5VDC. Unless the UBED offers some protection I'm not aware of, I don't need its capabilities of managing different input voltages. This shook my confidence of using the pins.

What are your thoughts on providing alternate power to a Pi? Can I do it through the pin header? This is my preferred solution. Are there any requirements I need to be aware of to make this an alternate solution?

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  • 0

    Pin header is cool, I've done it. I like to use 7.4V or 11.1V LiPos, and an adjustable buck power supply, fed into a diode , then to the Pi header pins.

    The buck PS can be adjusted for 5V + whatever voltage drop you get across the blocking diode. 

    I tend to overdo the battery size mA hr, if you just want to make it thru the track once , a baby size lipo, maybe  wire qty 2 150mAhr 3.7 V in series would do the trick. 

      https://www.etechnophiles.com/rpi-zero-2w-board-layout-pinout-specs-price/

    The DC-DC converter chip doesnt seem to have  significant transient protections built in. 

    imageimage

  • 0 in reply to robogary
    robogary said:
    Pin header is cool

    how did you do this, what kind of jumper wires did you use, one pin or 2? a Pi 4 can draw 3A, so the connector should be suitable for that. 

    The Chinese jumper wires from my junk box are certainly not.

  • 0 in reply to gpolder

    GP I would ask the same questions.

    My thoughts would be a wire gauge similar to what is provided in the DC wall wart.

    I appreciate the response but would feel more comfortable with a little engineering background.

  • 0 in reply to colporteur

    gpolder mentioned a Raspberry Pi 4,which I didnt use. I plan to followup in measuring the RPI 4 load requirements with a NOIR camera, WiFi on, and a keyboard dongle inserted. 

    I plan to repeat the same measurement on a Raspberry Pi 4 with WiFi on, a keyboard dongle, and an RPi  HD camera. I will use cheap chinese jumpers :-)

    The Raspberry Pi 4 schematics ( as well as other schematics) didnt publish the solder run ampacity. If I were to use both 5V pins, I would also expect at the least to use 2 ground points as well. I cant tell by looking if the 5V solder runs are beefy, and if some are beefier than others. 

    You have a RPi Zero 2W, different requirements. I found this article, the author stating a RPi Zero with WiFi only pulls 200mA, but the author also stated seeing other published loads of 300-400 mA. 

    https://robertthewombat.com/power-requirements-for-the-raspberry-pi-zero_w/

     ************** more on the wire itself ***********************

    Referencing this table. https://www.powerstream.com/Wire_Size.htm  

    Definition: ampacity is the current carrying capability of a wire. In other words, how many amps can it transmit? The following chart is a guideline of ampacity or copper wire current carrying capacity following the Handbook of Electronic Tables and Formulas for American Wire Gauge. As you might guess, the rated ampacities are just a rule of thumb. In careful engineering the voltage drop, insulation temperature limit, thickness, thermal conductivity, and air convection and temperature should all be taken into account. The Maximum Amps for Power Transmission uses the 700 circular mils per amp rule, which is very very conservative. The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle. For short lengths of wire, such as is used in battery packs you should trade off the resistance and load with size, weight, and flexibility. NOTE: For installations that need to conform to the National Electrical Code, you must use their guidelines. Contact your local electrician to find out what is legal!

    28 AWG is rated for 1.4A in this table. The "Neltron" Flat ribbon cable sold for for GPIO is 28 AWG. 

    26 AWG is rated for 2.2A,

    24 AWG is rated for 3.5A. The Dupont jumpers sold on Amazon are 24 AWG. 

    If your Pi is on a train, it will have loads for the camera & wifi. You'll probably use VPN to setup and connect to the Raspberry Pi thru a PC after the first initial setup. 

    -------------------------------------------------------------------------------------------------------------

    I'm sure with some more internet surfing there will be other helpful information. 

Reply
  • 0 in reply to colporteur

    gpolder mentioned a Raspberry Pi 4,which I didnt use. I plan to followup in measuring the RPI 4 load requirements with a NOIR camera, WiFi on, and a keyboard dongle inserted. 

    I plan to repeat the same measurement on a Raspberry Pi 4 with WiFi on, a keyboard dongle, and an RPi  HD camera. I will use cheap chinese jumpers :-)

    The Raspberry Pi 4 schematics ( as well as other schematics) didnt publish the solder run ampacity. If I were to use both 5V pins, I would also expect at the least to use 2 ground points as well. I cant tell by looking if the 5V solder runs are beefy, and if some are beefier than others. 

    You have a RPi Zero 2W, different requirements. I found this article, the author stating a RPi Zero with WiFi only pulls 200mA, but the author also stated seeing other published loads of 300-400 mA. 

    https://robertthewombat.com/power-requirements-for-the-raspberry-pi-zero_w/

     ************** more on the wire itself ***********************

    Referencing this table. https://www.powerstream.com/Wire_Size.htm  

    Definition: ampacity is the current carrying capability of a wire. In other words, how many amps can it transmit? The following chart is a guideline of ampacity or copper wire current carrying capacity following the Handbook of Electronic Tables and Formulas for American Wire Gauge. As you might guess, the rated ampacities are just a rule of thumb. In careful engineering the voltage drop, insulation temperature limit, thickness, thermal conductivity, and air convection and temperature should all be taken into account. The Maximum Amps for Power Transmission uses the 700 circular mils per amp rule, which is very very conservative. The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle. For short lengths of wire, such as is used in battery packs you should trade off the resistance and load with size, weight, and flexibility. NOTE: For installations that need to conform to the National Electrical Code, you must use their guidelines. Contact your local electrician to find out what is legal!

    28 AWG is rated for 1.4A in this table. The "Neltron" Flat ribbon cable sold for for GPIO is 28 AWG. 

    26 AWG is rated for 2.2A,

    24 AWG is rated for 3.5A. The Dupont jumpers sold on Amazon are 24 AWG. 

    If your Pi is on a train, it will have loads for the camera & wifi. You'll probably use VPN to setup and connect to the Raspberry Pi thru a PC after the first initial setup. 

    -------------------------------------------------------------------------------------------------------------

    I'm sure with some more internet surfing there will be other helpful information. 

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