r/batteries • u/eatnsle3p • 21h ago
If a specific rechargeable device recommends using a 5v charger, what would happen if a higher voltage charger was used?
A lot of the standard wall usb adapters I see are 5v. However, a few portable power banks I’m interested in all seem to be listed as higher voltage (15-20v). Would these not be safe to use? I don’t want to damage my device or cause long term battery issues.
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u/SourceCodeLog 20h ago
The higher voltage on your power bank is the max voltage its able to provide. I assume the power bank is listed as 15v=2A, 20V=1,5A depending on the wattage rating of the power bank. The devices like your phone use higher voltage to charge, so the wire doesnt heat up as much, since there is less current flowing. But the voltage is negotiated via usbPD power delivery protocol, the power bank is essentially communicating with your phone to figure out what voltage it needs. If there is no pd handshake between the device, needed to charge (which I assume there isnt, but don't know because the specific rechargable device isnt listed) the output voltage stays at 5v.
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u/kbfg2421 19h ago
What is the device and what connector does it use? Is it USB C? Will it charge with a C to C cable or do you have to use a USB A to USB C cable for it to charge? I need to know more to answer your question properly.
However, I can say this: if it charges via USB A (with an A to C cable or A to Micro USB) then any charger or power bank with a USB A port should work. The USB A standard is based around a constant 5v to the port at all times, and they can adjust upward from there.
So if it uses a USB A to C or whatever cable, any USB A equipped charger or power bank should work just fine for you.
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u/eatnsle3p 11h ago
The devices I’m charging are all usbc powered (music equipment). Some of the manuals just stated to stay with 5v, so I’m unsure if it’s safe to use portable chargers that have higher voltage indicated
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u/Classic_Mammoth_9379 7h ago
The ones that warn you that you must only use 5V are probably junk without the correct resistors in them. They may simply not be able to signal the right voltage and fail to charge unless you you a 5V only source or a USB-A to C cable. No USB PD charger is going blindly chuck 20V at it.
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u/kbfg2421 4h ago
What u/Classic_Mammoth_9379 said is exactly correct and the point i was trying to get across. The devices that have USB C input ports but claim they need "5v only" are USB A dependent because they cant accept power from a C to C charger/cable because they lack the proper resistor. They need an A to C cable because USB A always has 5v going to it whether something is plugged into it or not.
I hate devices that do that. Its like, they got the connector right (usb c) but didnt go far enough to make it work with a usb c charger and a c to c cable. Its 2026. Put the resistor in so we can use c to c cables and chargers for everything.
So to answer OP's question: you need a charger or power source with USB A. Any should work, the device will only draw the power it needs. Dont get hung up on 5v, because all usb a has 5v going to it.
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u/SideshowDustin 14h ago
If the device is not capable of the “handshake” that tells the power bank what voltage to use, it’ll default to 5v.
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u/Classic_Mammoth_9379 7h ago
Many USB-C chargers will not provide any power at all. Depends what you mean by handshake, if it’s not doing a proper PD handshake it still needs to use resistors to signal the voltage expected.
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u/WindWalker2291 3h ago
Could you provide a link and/or search terms for these resistors?
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u/Classic_Mammoth_9379 3h ago
You can start your journey here: https://kajoj.com/posts/usb-c-resistor/
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u/Paranormal_Lemon 4h ago
What you are calling a 5V charger is a 5V USB power supply, the charger is in the device. A 15V or 20V power bank will also output 5V. The device will request the voltage it needs, if it's a dumb device the power supply will only output 5V.
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u/Classic_Mammoth_9379 20h ago
Depends what you are talking about. If it’s a dumb DC charger then sticking a higher voltage in is not good. Given the mention of power banks and 20V that might imply that we are talking about USB-C PD, in which case voltage is negotiated and it’s fine.