compnaion wrote: ↑
Tue Apr 09, 2019 1:42 pm
That charger is too expensive it is like buying a 300$ charger for a phone that has a price of 1000$.
Define too expensive?
I have 2 of the official power supplies, and they only cost me $8.99 each. That's cheaper than most phone chargers I own.
The difference between 5V/2.4A and 5V/2.5A is half a watt (12.5 vs 12 watts). Assuming your charger has stable voltage regulation (see below), and you have a good, low resistance micro USB cable delivering the power, that half a watt is negligible under all but the most extreme loads.
It breaks down like this. The SoC can draw up to 1.3A under full load, and the USB ports are spec'd to deliver up to 1.2A (all 4 ports combined, with no per-port limits). So in theory, a headless 3B+ with nothing else attached could run from a good 1.5A power supply (but I would not recommend it). This is why some people get away with using 2A power supplies (which have roughly 700mA of headroom). 2A will work until you connect a power hungry USB device or HAT, and then the trouble starts.
jamesh wrote: ↑
Tue Apr 09, 2019 2:54 pm
I have used a Motorola fast phone charge on a Pi with no problem, so it really depends on the quality of the charger and the cable. But as others have said, the best option is to buy a dedicated power supply.
Yup, you not only need a good charger, but also a good power cable. Standard micro USB 2.0 cables aren't designed to deliver much more than 500mA without voltage loss. So you not only need a charger with good regulation, you also need a micro USB cable that can deliver the current needed by the Raspberry Pi (which can be up to 2.5A for a 3B+ model with a heavy software load and power hungry accessories). Cables included with tablets and smartphones are usually rated for higher curren (there are fast charge cables rated for up to 2.4A).
Also note that longer cables have more resistance, so you want to avoid long micro USB cables. If you need to power a Pi that's not near an outlet, use an extension cord to move the PSU closer (or find an alternate solution, such as POE).
So, yes, phone chargers *might* work. The problem is, you can never be sure unless you properly load test the charger, and most people don't have a constant current load tester. This is why they are not recommended. I myself have a couple of RAVPower chargers that work great , but they cost me double the price of the official PSU. I suppose that depends on wherre you live and who you buy from, but in my case the official PSU is the least expensive solution that works.
My mind is like a browser. 27 tabs are open, 9 aren't responding,
lots of pop-ups...and where is that annoying music coming from?