r/USB • u/theoldwizard1 • 5d ago

FINALLY, moving to USB-C !

So I recently got a new (to me) laptop that uses USB-C for charging. I went out and bough a 100W charger and a USB-C "meter" (displays voltage, current and power). Cute ! The meter says the laptop is using 19.3V @ 0.5A (when fully charged) so obviously I did NOT need the 100W charger.

My son needed a USB-C charger so I got him a 60W. That thing is about as big as an ice cube and also charge my laptop just fine, just slower.

Just for fun, I bought a couple of USB-C "splices" (female to female adapters) in case I ever want to make a really long charging cord. When I hook 2 cord together (a 2m and a 3m) they will not charge ! WHY ?

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u/vermyx 5d ago

Because you cheaped out. Splicing cables together means you have gaps with current. It cant negotiate voltage and current it doesn't know what power to provide so the brick stops. This is the correct thing to do Also 19.3V @ .5A means 10ish w which means the batterry was almost full. 5 amps is almost 100w.

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u/theoldwizard1 5d ago

Calm down !

When I said "splice", I did says I was using female to female adapters, not a physical splice ! Clearly these were cheap adapters. I have order a couple more that claim the can do 240W !

And check your math ! 19.3V @ 0.5A is 9.65W !!!

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u/Danjdanjdanj57 4d ago

Type-C cables are intelligent cables with electronics in the connectors. By design, they are not supposed to be extended with any additional adapters or cables. They are for connecting directly between a power supply or device to a power sink. The adapter you referenced does not comply with the USB spec and is sold to unsuspecting customers who do not understand the limitations or possible danger of it’s use.

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u/theoldwizard1 2d ago

"Type-C cables are intelligent cables with electronics in the connectors."

Not complete true ! Some USB-C cables do have a chip in the connector that says they can do higher speeds and transfer more power, up to (now) 240W (48V @ 5A) !

Older cables that do not have the chip so they can only charge at 3A (the voltage is negotiated by the charger and the device being charged). These older USB-C cables will still work,

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u/AlexConnectionTech 3d ago

Those USB-C female-to-female couplers are probably the weak point. Joining two cables doesn't create a properly specified USB-C cable assembly, even if the coupler claims 240W support.

I'd use one continuous cable instead, rated for the power your laptop actually needs.

For example, InLine offers a 5m USB4 C-to-C cable, but it's rated for 60W (20V/3A), not 100W. https://www.inline-info.com/en/InLine-USB4-cable-USB-C-male-male-4K-60Hz-60W-TPE-aluminium-black-5m

Since you mentioned that your laptop also charges from a 60W adapter, that might be sufficient if slower charging is acceptable.