Do external battery packs make speedlights recycle faster than they can safely shoot before overheating?

Question

I’m trying to understand whether an external power source meaningfully improves real-world speedlight performance, or whether thermal limits usually become the bottleneck first.

With Gen-2 Eneloop AAs, my flashes recycle in a couple of seconds at full power, but I suspect that if they could recycle much faster, they might overheat after only a limited number of shots. In practice I avoid this by using more powerful speedlights at around 1/8 power, where they can keep up with a 12 fps camera and rarely overheat.

So in general:
- How much faster can a speedlight recycle when powered by the best external/internal power options?
- How long can it sustain maximum-speed full-power firing before thermal protection or overheating becomes the limit?

I realize this probably varies by flash model, but I’m looking for the general relationship between recycle speed and heat limits.

user39420 · Answer

Unfortunately this is very difficult to answer.

I imagine this would be something like a table showing full-power cycle speed for each power source along with the number sequential full-power shots at that speed before hitting thermal limit.)

There is no table that can be found or created to display this kind of information, on a general scale. This is because of the specification and construction for every flash is completely different. The materials, quality and circuit type of a flash can greatly affect and change the number of possible shots before overheat.

In regards to buying the highest power flash, the most powerful guide number flash that I'm aware of is GN60/GN58 (at ISO 100) which is held by the the flagship Canon/Nikon flashes.

New Metz Digital Flash

You might find that something like a Metz flash or a Godox Wistro might have more power, however as a consequence you sacrifice size and portability.

Godox Wistro Flash

Just because you have a higher power flash dosen't necessarily mean that you can shoot at certain power levels for longer. This is a direct consequence of how the flash is designed to dissipate heat and channel the flash's power.

I would suggest that you try renting/borrowing several different flashes from various manufacturers and then comparing their performance.

You could of course try a more creative DIY approach which would involve adding external heatsinks and increased airflow in order to reduce the heat of the flash.

At that level even on internal batteries they can keep up with my 12fps body, and I almost never overheat.

By using the internal batteries of the flash,you are limiting the possible recharge speed of the flash. This will slow the flash down and not allow it to keep up with your 12fps body.

Can a speedlight work significantly faster than on its internal batteries without overheating?

Theoretically a flash can work indefinitely if the optimal power level is found. Aka you have found the balance between the flashes power and heat created.

A worthy note is that continuous lighting can be incredibly effective. Especially when using lights that utilise LEDs.

Do external battery packs make speedlights recycle faster than they can safely shoot before overheating?

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