How to supply external power to a flash?

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Chan Tran

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koraks said:
Not a divider; use a DC-DC buck converter. @Chan Tran knows; I'm not concerned.
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A divider wouldn't supply enough current and a divider would waste more power in the divider than to power the flash. Yes a buck converter is good but I really want to see how the batteries by themselves would work. What kind of current does the flash draw and what kind of voltage the batteries can maintain at the start of the recycling cycle. And no I don't care for the 283 because it has high sync voltage and I can't use it for my newer cameras.
 

eli griggs

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It's always good to hear a build, hack, modification does what the photographer/user needs it to do.

For me however, I still have my reservation on doing this myself, opting for other methods

I liked those Quantum battery packs and have one, battery needs replacing, with a fair lot of cables that fit Vivitar 283/285, etc flashes.

I suppose I should be looking out for battery dead Quantum units to refurbish or stick to RC batteries for rapid recharging.
 

MFstooges

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Quantum packs for sure can receive some hacking with Lithium battery. There's a reason Lithium batteries power electric aircraft. They are lightweight and your shoulder will appreciate that.

 
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Chan Tran

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I made 4 tests.
1. 4 AA alkaline batteries. Maximum voltage 5.89V Minimum voltage 2.92V. Maximum Current 3.1A. Recycle time 11.5 seconds.
2. 4 AA NiMH batteries. Maximum voltage 5.22V. Minimum voltage 3.18V. Maximum current 3.5A. Recycle time 10 seconds.
3. Power supply. 6V with 5A current limit. Maximum voltage 6V. Minimum voltage 3.75V. Maximum current 5A. Recycle time 5.4 seconds. Reduced to 3A limit recycle time 9 seconds.
4. 2 18650 Li-Ion batteries. Maximum voltage 8.28V. Minimum votage 6.19. Maximum current 12.2A. Recycle time 3 seconds.

AA batteries recycled about the same with NiMH slightly faster.
Power Supply is faster with 5A limit. If I were to limit to say 3.5A it would perform about the same as AA and should very safe.
2 Li-Ion (nominal 7.4V but at full charged they are near 8.4V and draw a whole lot of current. Recyle time really fast. I think it can damage the flash in this fashion. After the cap is charged then it's fine to leave it on for as long as you want but with every pop the initial current is more than 3 times the current with batteries.
I think I will use it with the power supply as I have to build a safe sync for it any way.
 
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eli griggs

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Thanks for the report.
 
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