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New Contributor
Posts: 3
Registered: ‎11-06-2019
Accepted Solution

Need info on setting up flash to use a battery pack

Recently purchased a Canon Speedlight 600 EXII-RT and a Bolt Battery Pack, and I'm trying to figure out how to use it.


I've been reading the Flash manual...and have done the C.Fn 12 set to 1.


Do you have to make changes to anything on your camera to use the battery pack? Or once you've used C.Fn 12 and set it to 1, you're good to go? I noticed on my camera I could do just about the same thing on it.

Also, once these changes are made, do I have to switch it back when I am NOT using the battery pack?

How do I know that the battery pack is being used instead of just the batteries in the flash itself? The image of the flash that shows when I turn it on isn't the image of the flash with the battery pack like it appears when looking at the C.Fn 12 area. Thanks for the info.

Product Expert
Product Expert
Posts: 915
Registered: ‎10-17-2012

Re: Need info on setting up flash to use a battery pack


Custom Function 12 set to option number 1 requires the use of external power for charging the Speedlite.  Internal power (batteries) are still required control the Speedlite.  Using setting 1 is useful to minimize the depletion of the internal batteries.  The Canon CP-E4N is the official one that Canon recommends, and the use of third party battery packs can cause misoperation or malfunction.  When using the CP-E4N on this unit you should see the little icon you saw in C.Fn 12 appear. 

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Reputable Contributor
Posts: 725
Registered: ‎12-24-2013

Re: Need info on setting up flash to use a battery pack

[ Edited ]

There is no need or requirement to use C. Fn 12 “1” when you use an external power source.  It is an only option.


If you leave C.Fn 12 at the default “0” the flash will consume power from the internal AA batteries and the external pack simultaneously. There is no notification that the external power pack is being used other than faster recycle times at full power pops. 


Most photographers I know leave C. Fn 12 at the default “0” because using the 4 internal AA batteries and external batteries together results in faster recycle times for the flash. 


The only reason to use C.Fn 12 “1” is too prolong the internal AA battery life while using an external power pack. Other than the selection of C.Fn 12 itself, there is no visible means to know that you have enabled C.Fn 12. You may notice slower recycle times and the batteries in your external pack will be consumed faster. 


If you do use it, there is no need to change it back if you remove the external power source. The flash will automatically revert to the 4 internal AA batteries if the external power pack is removed. 



Mike Sowsun
S110, SL1, 80D, 5D Mk III
New Contributor
Posts: 3
Registered: ‎11-06-2019

Re: Need info on setting up flash to use a battery pack

Thanks so much for the information.

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