I have an old device I want to charge via battery bank at 5V 1A. That’s what its original wall plug puts out.
The battery banks I have are 5V 2A, 3A or 3.2A.
What USB-A device could I use to convert those battery bank outputs down to 5V 1A?
Posted Nov 24, 2023, 9:49 PM UTC
You need to learn that Ohms law mate
current stepdown doesn't exist. whatever current the device charges at will be the current that the battery outputs
Thank you and forgive me I’m trying to understand. If current step down doesn’t exist, why on some battery banks do they have two usb A outputs. Both 5 volts. One at 1.0 amps and one at 2.2 amps?
one is rated to support UP TO 11W devices (the 2.2 amps) and the other one is UP TO 5W. if you plug in a 11W max device into the 5V1A it'll just draw 5W instead (if that amount supports normal operation).
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If you are happy with just 500mA i think this should work https://www.instructables.com/USB-Condom/
I can guarantee that this cable will not reduce the current to 500mA.
Doesn’t work. These are Apple devices and apparently need some kind of data connection to start charging.
Voltage is pushed, current is pulled
(Link to r/askelectronics Wiki)
Thank you. My device itself will pull around 2A at 5V. But I do not wish it to do so. That’s why I wish to convert my battery bank’s output to only be 5V 1A. Same as the wall charger’s output. Otherwise the device is taking in more power than I would like it to.
You don’t decide a device’s current draw.
Just out of curiosity, what is the device?
But if its power source only outputs a small current (1A) then the device cannot pull more than that, righ? Which is good in this case. I have old tablets and phones I like to charge slowly.
That’s how how electronics work, sorry.
You have a misunderstanding here.
When a supply says 5V 3A, that doesn't mean it puts out 3A, it means it puts out 5V, and it can put out up to 3A. You can think of the current rating like a capacity or weight limit. The supply doesn't decide how much current it puts out, the load does.
So if your load pulls 1A, it pulls 1A and the supply is fine. But a load that pulls 5A will break/blow/shutdown the supply because it went over the 3A limit.
"Science "--and by extension electronics--"doesn't care what you believe" or wish. (NDT)
It should be possible to engineer a buck boost converter with a constant current limiter. It would be complicated and buck boosts are generally not as efficient as boost or buck regulators.
It would be easier and cheaper to find a used device supplying 5V @ 1A on eBay.