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I have an external flash for my DSLR camera (a Canon Speedlite 430 EX II) that runs on 4 AA batteries. I plan on using this flash in a photo booth at a wedding, so it would be great if I could hack some sort of external power supply for this flash, instead of having to replace batteries several times during the day.

I saw several website describing ways of building "fake batteries" that allow to connect an external battery or power supply to cameras or flashes (for example, http://blog.davidburren.com/2003/03/flash-power-pack.html).

Would there be any danger/downside to building a fake battery pack that connects to an external 6V power adapter (for example a 6V 2A AC / DC power adapter)? How would you do it?

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Something you may want to think about is the fact that consumer flashes (like the Speedlite and Speedlight) are not always designed for high duty use, such as at weddings. You can burn out your flash, and plenty of people have done it! You basically have two options: if you treat your flash as disposable, you can work it hard, accept that it will burn out, and buy a new one. The other option is to buy a flash designed for higher duty. These flashes usually have bigger battery packs as accessories. –  Dietrich Epp Jul 22 at 18:14
    
Hopefully, it won't be used so heavily. I sill set the booth such that it takes 4 pictures in a row (with about 5 seconds between each shot), and I do not expect people to use it continually over the whole day. We'll see how the flash handles it, but I think this should not be too heavy. –  Wookai Jul 23 at 8:50

2 Answers 2

That works very well, but do keep in mind that some flash strobes take more than 2A from the battery pack (e.g. my 550EX peaks at about 2.7A when run directly from a bench power supply).

Another option - which I don't know if the 430EX II supports - is to attach a HV power supply that directly charges the flash capacitor, e.g. the Canon CP-E4. This reduces cycle time and is more efficient for the batteries (i.e. you need to take less batteries with you to get the same amount of flashes).

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About your first point, should I simply take a more powerful adapter, e.g. a 6V 3A? About the HV power supply, it looks like the 430EX does not support it. –  Wookai Jul 22 at 11:53
    
Yeah, a beefier power adapter than 2A should be fine, but you might just want to check first with a lab power supply or spare adapter before you purchase a new one. Too bad the 430EX doesn't support HV batteries, they are really badass for photoshoots. –  user36129 Jul 23 at 8:01

You can make a dummy battery with wires attached IF you are willing to provide access - either by slotting the battery door or leaving it open or ajar and arranging whatever it takes to make it work.

A large capacitor will help provide surges.

When running a DSLR like this I found the supply had to be much "stiffer" than I would have expected to handle current peaks - about 4A from memory.

Use of eg a lead acid battery or other very high current capable source just MIGHT result in damage. If the designer "knew"they could never get more than 10A peak they may design around this. So if you had an eg 100A peak capable source attached, something that usually survived an initial 10A charging blip may quail at say 100A. This is very unlikely to happen but you asked about worst case, so this applies. If using a lead acid battery, adding a small resistance to limit current may be wise.

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