So I'm using a Lipo to power my Pi 3 and to be safe, I installed a 5v 3A UBEC. Upon checking the voltage output, I saw the BEC was only stepping the voltage down to around 5.25v, rather than 5v. I know this is pushing the recommended max voltage. Do you think it will be Ok? Thanks!
1 Answer
5.25 V should be acceptable.
As noted in Raspberry Pi Power Limitations:
Power sources SHOULD provide 5±0.25V and often list a current rating
I couldn't find any explicit mention of voltage in the Pi FAQ, but it turns out that the voltage constraint is part of the USB standard. Note that the tolerance listed there is 4.40 — 5.25 V (in the sidebar).
See also in the RetroPie overclocking documentation:
The Pi runs off 5V but there's nothing wrong with a power supply providing 5.1V or 5.25V. There's usually about 0.25V drop over a typical USB power cable so the extra voltage helps compensate.
Increasing the voltage too much further could cause damage, but you're not in that range yet:
One way to increase that reliability is to increase the voltage to the component. This has the tradeoff that more heat is generated by the component. A component may be damaged if too much voltage is supplied.
As long as the heat doesn't get excessive, and you don't go above 5.25 V, you'll be fine.
answered Aug 24, 2017 at 18:36
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Thanks so much for the answer. There's one more thinf that I'm wondering. The BEC outputs power to just a simple + and - wire. What would be the best way to send power to the Pi? I know I can power it off two of the GPIO pins, but I have heard it's safer to go through USB. Should I use an existing micro usb cable and solder that to the BEC, or is there a way to hard solder the power wires onto the pads where the USB port is soldered to the Pi on the underside? Thanks! Commented Aug 24, 2017 at 18:49
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@RobRoberts Using the GPIO does lose some protections, yes, so I'd advise avoiding it if possible. Does the picture and advice in this answer help (mainly the bottom one with the USB adapters)? Commented Aug 24, 2017 at 18:52
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1@RobRoberts I would not lose sleep over powering the Pi with 5.25 V, not only is it within the USB spec that is referenced for the Pi too; it is also noteworthy that all on-board components are powered via a voltage regulator nonetheless, nothing to worry. WRT the question in the comments, I would suggest going through the micro-USB port. But please note that new questions should rather be posted as new question (unless they are already there, of course).– Ghanima ♦Commented Aug 24, 2017 at 18:54
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@RobRoberts You can buy a DIY micro-USB plug and solder your +/- wires to that. A bit tricky, but I've done it and it works great. Then you power through the Pi's usual connector and don't have to bypass anything.– BrickCommented Aug 24, 2017 at 19:26