Chance to run hotshoe flash via LiPo USB "power bank"?

[Jochen_S]

<p>Question aimed at contemporary electricians:<br>

My local supermarket caters those cased LiPo batteries intended to recharge smartphones in the wilderness pretty cheaply. they are rated 5V something about 2A, and 5 or at least 4Ah.<br>

I am wondering: could I wire one to an old hotshoe flash Vivitar 283, Metz, whatever to power it? <br>

My concerns: I am aware that a discharged flash draws a lot of current for a quick instant and LiPo batteries are somewhat limited (might for example burn if abused) and probably come with controler units to prevent the worst.<br>

Will I most likely blow a fuse inside the power bank when attempting to run my flash on it? Or is the device otherwise limited (like the high inner resistance of alkaline batteries) to allow comparably slow flash charging?<br>

Thanks in advance.</p>

[wayne_f1]

<p>I think trying to power the flash from these is a bad idea. Just putting batteries in the flash would be a greatly better idea. You can't do that for a cell phone, but batteries work really great for a flash unit. Just carry a few spare batteries.</p>

<p>The flash batteries power the electronics, and also run an internal power converter that steps the voltage up to 300+ volts, used to charge the flash capacitor (relatively slowly, during a second or two). Then when the flash fires, all the power comes from the flash capacitor instantly, not from the battery. The battery just recharges the capacitor.</p>

<p>You also need some battery compartment shaped connectors too. I vote for it being not a good idea.</p>

<p> </p>

[craig_shearman1]

Agreed. A lot of work reinventing the wheel to

get them to connected and the voltage correct

etc when there is a readily available solution

that already works just fine.

[Charles_Webster]

<p>Agree with the other posters. If your flash uses 4 AA batteries, with alkaline batteries the nominal voltage is 6 VDC. It's not likely your flash will work correctly at 5.0 VDC.</p>

[steven_clark]

<p>I think there's a pretty decent chance the flash would work as a manual flash when driven from 5v, but automatic exposure features would likely be suspect. Of course if the flash was able to run off NiCad batteries when released then a conversion like this would probably work perfectly as it would take a range from 6-4.8v. In that case I'd guess a conversion could probably be done for a Vivitar 283 at least. I'd use one of the bigger USB battery pack if attempting this. One closer to the size of a phone than a lipstick case.</p>

[wayne_f1]

<p>I'd guess 5V would work, NiMH is not higher (but NiMH can deliver current). The AA cells in a speedlight see at least 6 or 7 amps of current when recycling for a couple of seconds, which I doubt this USB device could deliver, so recycle would be quite slow.</p>

<p>If insisting on pursuing this for any practical effect, then instead use a 6V sealed lead acid battery. Still have to come up with connectors (and a charger), but it should work great, and fast, for very many shots. Here is one popular finished product: http://www.aljacobs.com/products-services-ordering/the-black-box-specification.html</p>

[rodeo_joe1]

<p>The maximum rated output current of a standard USB socket is 0.5 A, so there won't be nearly enough current to recycle a flash in any sensible time.</p>

<p>Also, I've had one of those cheap smartphone backup battery devices apart. The inverter circuitry (needed to convert from ~3.7 volt Li-Ion cells to 5v) looks cheap, minimal and badly put together, and gets quite warm even when used for its intended purpose. Expect smoke followed by a dead backup device if you try to draw the 5A+ that a speedlight needs from one of them. Incidentally, the cells commonly used are standard 18650 Lithium-Ion cells, as used in "vaping" atomisers and older laptop battery packs - not Lithium Polymers.</p>