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Everything I have read about the Raspberry Pi 3, model B says that it will not run reliably on anything below 4.6vdc. I have a Pi 3 and I am running it at around 4V DC with a single 18650 lithium battery. It boots up just fine on the Volumio 2 OS and it sounds wonderful. Can anyone explain why this is so?

I am not running any peripherals other than the Allo Boss HAT DAC. I know that the lithium battery has tons of headroom as far as amperage goes. I read this section on StackExchange which might suggest that only the HDMI port requires 5V DC:

Power In from the μUSB connector goes through a polyfuse and an ideal diode to provide 5V which is the 5V rail on the expansion header and provides all power to the Pi including the following:

Power in: a dual step-down converter (PAM2306) which provide 3V3 and 1V8 via a MOSFET to 5V_CORE and a Step-Down Converter (RT8088A) which generates the VDD_CORE (nominal 1.2V). This was performed by the SOC in the original Pi. voltage monitor chip (APX803) Power Switch (RT9741) which produces H5V for HDMI

The Richtek RT8088A and RT9741 listed above both have an input voltage range of 2.7vdc to 5.5vdc so that's good.

Any opinions?

  • Lithium-Ion batteries experience voltages that fall over time as they are discharged. It may be 4.2 fully charged, but it is 3.7 nominal. I would recommend 2 is series and then use a cheap buck converter to get a stable 5volt supply as the battery voltage decreases over use. – Clement Sep 15 '17 at 19:31
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No one has said "Raspberry Pi … will not run on reliably on anything below 4.6vdc"; in fact the Pi itself will run until the voltage falls below the drop out voltage of the regulator. It should work reliably down to 4.2V, and I have done so in testing.

Actual components vary, what works on one Pi may not on another. I once worked with a major telecommunications manufacturer, which used 80286 processors to perform most tasks - but they individually tested each chip to select those which could be pushed beyond normal safe parameters.

The regulators are step-down converters; they will work on lower voltages BUT will NOT boost the voltage, and regulation will drop off as the input voltage falls.

The USB and HDMI use 5V, and may not work, again this depends on the external devices; many do not need power or work at low voltages.

I think a single Li battery is marginal, as at maximum it too low, and will drop with time.

See Raspberry Pi Power Limitations for detail, although you seem to have quoted from this.

You can run your car without oil for quite a while, but I would't recommend it!

Buy one of the cheap boost regulators which produce 5V from a LI battery.

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