[amoringello]

Anyone ever use an alternate power supply to power their flashes?
I've got to do a 7 hour shoot in a month with three flashes (AF360 and AF540).
I'm not looking forward to changing batteries every hour or less.

No mains power, so I'm stuck with off camera flash (or renting battery powered strobes... which I may need to do but would rather work with what I already have!!!)


I'm looking to hook up one of those backup power supplies -- essentially a large capacity rechargeable batteries (they often come with 120V line and 12V car battery connectors built in).

I was thinking of wiring up a "fake" battery pack for each of the flashes and running them off the big battery for the day.

Just wondering if anyone has done this or seen/heard of others powering flashes off anything other then AA's or the *expensive* and hard to find TR-3 pack (which also does not work on anything other than the AF540).

Thanks for any info or insight!

(edit) I should add, this is in a booth situation, so everything is static. Stringing cables is not a problem as long as I tie them up out of the way. (It is for charity and do not expect to make much money for myself, so renting strobes is truly a last ditch option)

[Adam]

Perhaps you missed this accessory: PENTAX TR Power Pack 3 - Pentax Accessory Review Database - Flashes, Grips, Camera Bags

Sounds like just what you're looking for- except that it still uses regular C batteries. Should still easily last for an entire day, though.

The AF540 normally takes 4 AA batteries, which is approximately 10800 mAh (2700x4). The TR power pack will have about 48000 (6x8000) mAh with alkaline batteries, so you're looking at at least 4 times as much power.

[rhodopsin]

Perhaps you missed this accessory: PENTAX TR Power Pack 3 - Pentax Accessory Review Database - Flashes, Grips, Camera Bags

Sounds like just what you're looking for- except that it still uses regular C batteries. Should still easily last for an entire day, though.

The AF540 normally takes 4 AA batteries, which is approximately 10800 mAh (2700x4). The TR power pack will have about 48000 (6x8000) mAh with alkaline batteries, so you're looking at at least 4 times as much power.

Um, I may be wrong, but those batteries are connected in series not parallel, so the Ah do not add together, but supply a higher voltage at the individual battery Ah. That would make the C batteries provide 8000mAh/2700mAh=2.96 or about 3 times as much power, giving about 3 times the operating time, so C batteries will need to be changed at least twice in 7 hours given AAs last 1 hour or less.

Also, OP already knows about the TR-3, but considers it 'expensive'.

@amoringello, your idea of 'fake' battery pack will work as long as the voltage is correct. For 4 AA batteries in series that is 4.8-6 volts, so you need a 6 volt large battery, not a 12 volt. Then there is the problem of passing the wires through the flash battery cover. I suggest that changing the AAs in the three flashes every hour or so is less effort than rigging up a homebrew alternative, ymmv.

[Steinback]

I have a 6 volt sealed lead acid (SLA) battery pack that I can hook up to either of my Vivitar 285 flashes with an OEM Vivitar dummy battery and remote cord. Many 285 users who do extended shoots build their own dummy batteries using wooden dowels the size of AAs wired together with contacts in the appropriate places and one large SLA battery hanging from each of their flash stands.

That approach might get a bit pricey for 3 flashes and just one event. Look up the battery spec sheet from the manufacturer to figure out how much current you can draw over a given time before the battery drops below 6 volts and that (with a safety margin) compared to the output of 4 AAs will give you some idea of how large an external battery you need for each flash.

[amoringello]

Good point. I guess I could get a small power brick to bring the power down from 120v to 6v.
Rather inefficient for the battery drain. Getting 6V lantern batteries might work???
Any issues with amperage? I guess I could give those a try, they are usually just a bunch of AA or C batteries tied together anyway. Would be easier than lugging a 30lbs battery. :-)

And good catch, yes I am aware of the TR3. It increases time of use but does not significantly increase recharge rate. Essentially connects C cells in place of AA, but dunno why it plugs into high voltage port. At $200, it seems excessively expensive for little gain.

[rhodopsin]

Alkaline AA battery capacity is less than 1Ah (=1000mAH). Given your use of flash that Alkaline AA batteries last less than an hour, to last 7 hours requires at least 7 times the capacity, or 7Ah. 6 Volt 12 Ah Sealed Lead Acid Battery: BatteryMart.com You'll also need 6 Volt 500 mA Sealed Lead Acid Battery Charger: BatteryMart.com and Sealed Lead Acid Battery Charger Cord: BatteryMart.com

And a fuse (never ever forget the fuse -- a shorted battery can cause fire or even explode, or melt wire throwing molten metal!) INLINE FUSE HOLDER & 10A FUSE-MPJA, Inc.

A far less expensive (and much safer) alternative to batteries, if you have 120VAC available, is to use a 6V regulated power supply, such as Power Supplies, Plug Supplies, 6VDC@1.66A PLUG SUPPLY, 18477 PS Those are inexpensive enough to get one for each flash.