Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
09-02-2010, 06:48 PM   #1
Veteran Member
amoringello's Avatar

Join Date: May 2008
Location: Virginia, USA
Photos: Gallery
Posts: 1,562
Alternate power supply for flashes?

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)

09-02-2010, 07:33 PM   #2
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 51,593
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.

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:
09-02-2010, 07:55 PM   #3
Veteran Member




Join Date: Dec 2009
Location: Deep Forest
Posts: 643
QuoteOriginally posted by Adam Quote
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.
09-03-2010, 12:09 AM   #4
Veteran Member
Steinback's Avatar

Join Date: Jan 2008
Location: GTA, ON, Canada
Photos: Gallery | Albums
Posts: 1,673
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.

09-03-2010, 02:11 AM   #5
Veteran Member
amoringello's Avatar

Join Date: May 2008
Location: Virginia, USA
Photos: Gallery
Posts: 1,562
Original Poster
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.

Last edited by amoringello; 09-03-2010 at 02:23 AM.
09-03-2010, 07:43 AM   #6
Veteran Member




Join Date: Dec 2009
Location: Deep Forest
Posts: 643
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.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
af540, batteries, battery, flash, flashes, hour, lighting, pack, photo studio, power, strobist
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
MZ-S battery supply? Gooshin Film SLRs and Compact Film Cameras 24 12-21-2008 02:22 PM
D-AC76 Mains power supply for K-200D dncraker Pentax Camera and Field Accessories 1 12-19-2008 01:48 AM
Possible DIY portable Power Supply for Studio Strobes - ADVICE NEEDED MRRiley General Talk 4 09-11-2008 05:40 PM
Charger/Power Supply jnorth Pentax DSLR Discussion 15 01-07-2007 10:47 AM



All times are GMT -7. The time now is 11:26 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top