I'm looking to build a DIY battery power-supply for my Raspberry-Pi3. My electronics engineering skills are intermediate/novice, and as I had began research on the project, I ran across the following excerpt from a web-article about powering the Raspberry-Pi directly via it's GPIO pins:

"A more technical (and of course dangerous) way to power the Pi is directly via the GPIO. It should be noted that, unlike the Micro-USB port, there is no regulation or fuse protection on the GPIO to protect from over-voltage or current spikes. If an incorrect voltage is applied, or a current spike occurs on the line you can permanently damage your Raspberry Pi. At best, you’ll “burn out” some or all of the GPIO pins, at worst you can fry your Pi! So be careful."-modmypi.com

Can battery power source cause power-spikes or over-voltage? Should I be considering regulation?


Discard that website. The infomation they give is ill-advised to wrong.

You cannot power the Raspberry Pi through the GPIO pins. You can power it through the power pins of the 40-pin header. The only difference between doing that and using the Micro-USB power input is a fuse in the +5V line. As the +5V line is routed directly to the other USB ports, you can burn out the copper traces on the Raspberry Pi board if you use a powerful power supply at the 40-pin header and produce a short circuit on the USB ports.

The other traces on the board are protected by the fact they are behind voltage regulators with built-in current limiting.

"Burning out" GPIO pins happens when clueless people connect too high loads to them, or connecting them with +5V or even higher, instead of at maximum +3.3V. This isn't related to the +5V power supply.

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    \$\begingroup\$ I believe the cited verbiage just misuses terminology, and means to power the PRi via the "40-pin extension GPIO header", which does have +5V rail exposed, as you described. But I strongly support your sentiment on first line. +1 \$\endgroup\$ – Ale..chenski Mar 22 '18 at 1:23
  • \$\begingroup\$ You say "Connect to high loads to them.", is there an exact number I should be shooting for with the supply voltage, like +5.1V? Do you know the Pi's tolerance? Thanks. \$\endgroup\$ – Iam Pyre Mar 22 '18 at 1:24
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    \$\begingroup\$ @IamPyre, since the +5V is shared with downstream USB ports, you can safely go for 5.25 V (or even 5.5 V) if you wish. The internal PMIC (PAM2306) is tolerant up to 6.5V. But why do you plan "to shoot" to anything other than +5 V ? \$\endgroup\$ – Ale..chenski Mar 22 '18 at 2:02
  • \$\begingroup\$ "High loads" means people try to draw/sink more than 20mA from a single pin (or in sum more than 200mA from the chip), e.g. by connecting a motor directly to the GPIO. This won't work. \$\endgroup\$ – Janka Mar 22 '18 at 2:14

You can experience current spikes from capacitor banks charging upon initial power application. The caps behave like short circuits for a very small amount of time. On board with large banks, I've seen this blow quick-burn fuses on the board if the power supply is not current limited by design. This is especially true of batteries which often will can dump large amounts of current.

Linear regulators (like a basic 7805) are generally very safe if you operate them within the voltage input limits. Switching mode supplies require a little more attention to detail (sometimes a minimum load to maintain the correct output voltage). However, as long as you read the datasheets on what you are using, you should be fine.

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  • \$\begingroup\$ A 7805 running a R-Pi will need a heatsink for sure. \$\endgroup\$ – Brian Drummond Mar 22 '18 at 10:05

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