Power Supply questions/issues
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I have a Pi 3B+ that I haven't used in a long time and was going away on a trip for a week and wanted to bring it with me to game when away rather than use my tablet or plug in laptop. I took my Samsung SD card (not a fake) 32 gigabytes and put latest retropie 4.8 and installed with Etcher and used a official power supply and it seemed to boot but I didn't test any further and assumed it worked.
When I arrived on my trip I plugged in the Pi and used a power brick that has 3 usb connectors, it shouldn't be a power issue as this supply can power laptops, I used 2 diffferent cables, all connectors and when booting the Pi gives a message about inadequate power or something and the lighting symbol and I tried testing a Mega Drive game, and it ran laggy.
The next day I borrowed another brick in case the one I was using as it was a multi usb and meant for PD and high powered devices was too powerful and that didn't have the error on boot but games were still laggy, spec of this brick is 5v = 2.1A
Outside of waiting until I get home to see if the official power supply works is there anything else I can do? And I assume I will get issues with the setup I used
Oh and before I forget its in a MegaPi case that may affect power.
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First problem, The pi could not care less about PD. It can’t use it. It uses 5v, and It will use whatever the max amperage is on the 5v delivery. And it needs be at least 2.5 A. You May be able to get away with 2A with light duty, but it’s rated to use 2.5 A.
Second of all, you need to maintain the 5v. Generic USB cables typically can’t handle high current and maintain 5v. The cables are too thin and you will get voltage drops. Also a lot of phone battery chargers, don’t maintain 5 V that well themselves because they don’t need to. A battery charger circuit doesn’t really care if the voltage drops, it’ll just charge slower and you waste a little bit of energy. But if you look at the official Power supply for the pi, you’ll see how thick the cables are going to the connector. The thicker the cable, the less resistance, and the less likelihood of a voltage drop. And a better regulated power supply to maintain the 5 V is needed. -
@lostless I more meant it being a higher quality brick that had PD in rather than a cheap nasty device, the cable I use was a thicker cable I paid about £8 for on Amazon. I know thickness of cable and price isn't always a indicator but the build quality did seem there.
Oh well at least I know for the future.
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@suikodentir basically how PD works is that You can send more power (watts) over thinner cables by upping the voltage and lowering the current, Which is great for devices that can take it. So the cable may be high quality, but may not be thick enough to carry a high enough current at 5 V . which is what the pie requires. And the longer the cable you have the worse the resistance gets.
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@suikodentir The official pi power supply is 5.1V 2.5A 18AWG wiring. Probably to compensate some loss so the pi can reliably get 5V.
Also, chargers can be unreliable with supplying a steady amount of power.
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FWIW Here [1] is a list of tested USB Chargers, this guy also runs a section on how he tested (see notes at end of page) and how these chargers are built usually.
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