On 25/01/13 18:06, Anthony Anson wrote:
On 25/01/13 17:41, Mark Rogers wrote:
I have several 5V USB supplies, which if the labels on them are to be believed will supply anything from 1 to 2.5A, although I have serious doubts that I can believe the labels. Based on how sowly they charge my phone I think some that are labelled 2.5A are more like 200mA... They're from various sources, which include the likes of eBay. Some will power my RPi, but only if I don't try to plug in a USB device as well.
Assuming very little in the way of electrical knowledge (which I guess is obvious as I don't know the answer to my question), what's the "best" way to see what current a power supply can deliver?
Further, and which might save you a lot of time and money, use your multimeter to check the voltage of the supply (across the + and - lines) before and during charging.
If the voltage drops below what is required, *that's* the prompt to raise the output capability.
It's the impedance/resistance of the device being supplied which determines the amperage, not the rated output of the PSU.