With the newest version of Apple’s mobile operating system, iOS 13, you can now easily connect external hard drives (e.g. USB thumbdrive, keyboard, mouse) and manage files directly from your iPad or iPhone.
If you are using an adapter cable to connect a USB hard drive to your iOS device, you may be greeted with either of the following error messages:
Cannot Use Accessory
USB Flash Drive: This accessory requires too much power
Cannot Use Device
The connected device requires too much power
Why do I see this error message?
This error message is shown because your external device you are trying to connect requires power in order to function properly. The Lightening or USB-C port on your iPhone or iPad only will make a limited amount of power available to external devices. The error means that the external device you are trying to connect requires mores power than your Apple device can give: the maximum is 100mAh.
If the error message keeps popping up on your device, you may try to perform some actions first in order to resolve the issue.
Best thing to do is to first disconnect all cables that are plugged in. Plug in the adapter cable again, then connect the external device. Make sure each cable is connected firmly so that there is no weak or interrupted connection.
Another option you may try is to reboot your iPhone/iPad/iPod, both with and without the adapter cable connected.
A third option is to make sure your Apple device is fully charged.
Try another device
If you are still having trouble with the error pop-up, there are still some options to try out. First, you may check if the same error is shown on another iOS device.
Or, try another external device. Another USB thumb drive or external hard drive may work perfectly.
The last option here is to try a totally different device: more concretely, a very ‘simple’ device such as a keyboard. If the keyboard (which is a simple device and doesn’t need much power generally speaking) is working fine, it is likely you should keep reading.
Use a an adapter with a power supply
The last option remaining and your best option you have is to use a OTG adapter that has an additional power supply port available. This means that there are two ports in total: a data transfer port for your external device, and a power port (which will both provide additional power to the external device, and it will charge your iOS device).
Thanks to the external power source, the external device you connect can now draw up to 500mAh, which is 5 times as much without extra power source.