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iOS devices will outright not charge if there’s just 5V on the port. Even the lowest charging current requires some sort of resistor arrangement.

Fortunately it seems like bridging the two data lines (essentially a 0 ohm resistor) is what’s needed to allow high-current charging (I think it’s 2 amps), so as long as your supply can withstand it (which pretty much every single device can, given that it’s tied to its own 5V rail which can supply many amps) you can just bridge the two pins together. Worst case scenario the overcurrent protection on the port will protect the source device.

There's a fast charge dongle for this. Portapow makes one.

Looks like there is a StarTech one too with a button to change modes - search for USB2CHADP (although currently out of stock at Amazon).

Jeebus. Might be easier to wire in a 12V compatible USB charger in that case.