Wires overheated while charging iPad with ATX PSU

Remember, D+ and D- are shorted to show the port is a dedicated charging port (DCP).

I expect the iPad can draw a fair amount of current, and the ATX PS could certainly supply it. How thick are the conductors?

Sylvia.

I wonder what the actual voltage is.

Presumably 5V, unless you're thinking that it's drawing too little current for the ATX PS to be stable.

Sylvia.

Some "USB" (irony emphasis on the U) cables are specifically resistive, to limit current.

I'd expect that an ATX switching supply might make a lot of voltage with a light load.

OP could measure both.

tirsdag den 22. februar 2022 kl. 20.30.01 UTC+1 skrev John Larkin:

examples?

can't see any reason to a USB cable being resistive other and as a side effect of trying save money on copper

A VOM seems like the easiest way to VERIFY that.

You may find the PSU requires a heavier load on the supply than you are providing.

Putting an ammeter in series with the load to give you a rough idea of the amount of current flowing would be a good idea. Likewise, the voltage DROP across the cable's length.

iPad get warm (battery)?

If you disconnect iPad from your "adapter", there should be NO current flowing and no "heat", right? (i.e., wiring error)

I've seen gadgets that come with a specifically resistive USB power cable and warnings to use only that one. I don't have a link.

Seems like a good way to destroy the ipad.

In that case it isn't a USB cable. Its something else with USB-style connectors.

John

Aren't they all?

USB is a mess.

tirsdag den 22. februar 2022 kl. 22.36.05 UTC+1 skrev John Larkin:

no, random Chinese dothats convinnietly powered by the 5V from a USB port is not USB

how so?

I don't think computer supplies work that way. They either regulate or shut down. The problem is keeping it working while running a relatively light load. However, 3 amps is not a uniquely light load for a PC supply. I don't think that is the problem. Much more likely is the supply is providing all the power the iPad is asking for and the wires are too small. Or maybe the connector contacts are bad and the OP is feeling the heat there.

In an ideal world, certainly.

But who knows what some cheap PS from China might do? Not that I'm saying that the OP has such a PS, but anything is possible.

Sylvia.

Of course, everyone leaves out unneeded parts, so the design that suits PCs is a circuit that requires a minimum load (not sure from which voltage). The supply does not go out of regulation in the sense of overvoltage. It does not output current on all outputs. There is no reason why it would overvoltage because of a light load. But, as I've mentioned, the iPad is not going to draw a light load and obviously *is* drawing a heavy load, at least for the wires being used.

There are a zillion barely-different but incompatible connectors, nearly all with non-obvious polarization.

The C connector scheme is pretty good... decades late.

iPad battery is OK, it's the USB wire that gets hot,

But, with the iPad electrically NOT connected to the "adapter" that you've made, do the wires get hot?

I.e., if you've accidentally miswired/shorted the adapter in your construction attempt, then the "fault" may be independent of the iPad's presence.

(actually having *numbers* for V and I would *really* help you!)

The battery may not be OK for long!

Why not use the right iPad charger?