Can you use a new 5.1v 3a psu on a pi0?

I need to get some new psus for an old zero and a pi zero 2. Would the new psus increase in amps mean that it definitely shouldn’t be used with older pi’s? I’m thinking I’d rather buy a psu now that can be used for the pi4 later. Obviously I’d also need a little usb c to micro usb adaptor too.

Any help much appreciated.

The amps rating of a power supply is how much they are capable of providing - think of it as the maximum flow of water through a tap/faucet.

The consuming device takes what it needs (opens the tap only as wide as it needs).

So having a power supply with a higher max Amps than is needed by the device is OK.

Different story for voltage - make sure they match.

Also - double check the connector is the same … mini usb v micro usb v usb-c
or have a suitable usb converter.

Thanks for the reply. That’s my understanding too. The newer psu is 5.1v as opposed to 5v on the older one. That should be within a reasonable tolerance shouldn’t it?

The 5.1 is so that you see ~5.0V at the Pi end of the cable under high current draw. The resistance of the wire (small as it is) drops a little of the voltage under high current. 5.1 V won’t hurt a Pi Zero. The newer Micro USB supplies are 5.1v 2.5A output.
Raspberry Pi 12.5W Micro USB Power Supply (for Pi Zero 2 W, 3 B+ and e - Pimoroni
And it looks like the older ones are also 5.1v
Official Raspberry Pi Universal Power Supply (Pi 3 & Zero Only) - Pimoroni

Just FYI, what he said regarding current draw applies. The device only draws what it needs. And can’t draw any more than the rated max of the supply.
I have a 5V 10A switching power supply that I power multiple Pi’s from. I made up my own custom cable which splits to 3 micro USB and 1 USB C. What gets plugged in varies from combinations of Raspberry Pi’s and Pi PICO’s.

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Thanks for that @alphanumeric A new pi 5.1v 3a psu it is then, with a usbc to micro usb adaptor. :)

I’ve gone the other way when need be. 2.5A Micro USB power supply with a USB C adapter to a Pi 4B. I was able to get a Pi 4B but the Pi 4 power supplies were out of stock. If I had waited for the power supplies to be in stock the Pi 4’s wouldn’t have been. ;)

Even working hard a Pi 4 isn’t going to reach the 3A or 2.5A limit. Not by itself anyway. The 3A limit is there for the power hungry peripherals like motors, servo’s, etc.