I attached the Compact Battery Pack CP-E4 to my Speedlite 600EX-RT and it will not power on. The battries are fully charged. The flash works with the battries installed in the flash unit. Is there some thing else that I am suppose to do?
Thank you for posting about this.
When using the CP-E4 with the Speedlite 600EX-RT, it is still necessary to have batteries inside the battery compartment of the flash. The flash needs internal power to function and allow you to control the flash. With the CP-E4 connected, it will draw power from it and the internal batteries to recycle the flash.
Even though internal power is necessary, you can still set the flash to draw the recycling power from the CP-E4 only by changing Custom Function 12 to [1:External power only].
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