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Old Aug 6, 2003, 8:39 PM   #1
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Default Homemade Dry Cell outboard power pack?

Any good reason why I can't take a standard dry-cell battery, stick it in a fanny pack, connect via a homemade alligator-clip to camera-plug extension cord to my digicam and laugh at the internal batteries? I presume there is at least some overvoltage protection on digicams, because a fresh set of 4 alkalines produces more than 6 volts... Anybody tried this? Seems much cheaper than the manufacturer's auxiliary battery packs.
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Old Aug 6, 2003, 9:23 PM   #2
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I have seen some discussions on other forums of people using C Cells and building battery packs that they then put into old leather cell phone belt cases.

It wasn't as simple as I would have thought, though. I would be careful. Of course, I don't have the link to that any more (wish I did!) but they made a circuit to go with it.

Eric
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Old Aug 6, 2003, 9:47 PM   #3
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Hi again Eric! Since the lantern batteries are already rated at 6 volts, I shouldn't have to use a voltage regulator, surge suppressor, or amp-limiter. It should be a straight hookup. The factory AC adapter is a 6 volt unit, at about 1.5 amps, so this should be the same, yes?
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Old Aug 7, 2003, 12:12 AM   #4
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I thought about C and D cells too but opted for a sealed lead acid battery (SLA) solution. *Double the amp hour rating of the SLA to compare to NiMh because they are rated differently on discharge*. Droped the two batteries in a fanny pack and I am ready for a three week trip into the jungle with my waterproofed Fuji 2800. I worried about using the raw ~6V vs the 5V external wall wort rating, but everything is working fine without any added voltage regulation. $32US including smart charger, 2 batts, cables and fanny pack.

Besides for the size and weight of SLA packs, which aint really that much, I don't see an option for extended use away from an AC outlet. I'm guessing a comparable pile of NiMh packs would weigh as much as my solution but with a sizable daily discharge without use.
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Old Aug 7, 2003, 1:33 AM   #5
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A clutch of four C or D disposable cells will differ from the same number of AA cells only in size, weight, and amp-hour capacity, so there's nothing wrong with making an external battery pack, so long as a decent connector can be constructed.

As for sealed lead acid, I had one of these about 10 years ago for my Sony camcorder. At the time Ni-Cd batteries seemed to fail all too repidly, and Ni-MH were very expensive. SLA was a good, if heavy, solution, especially as they're tolerant of long-term trickle charging at constant voltage. However, they are very intolerant of deep discharge, which is quite likely to happen with camera applications, and mine didn't last as long as I'd hoped.

As I see it, Ni-MH, now they're cheap and tolerant of top-up charging, have superseded SLA.

Has anyone brave tried using a clutch of 5 Ni-MH cells instead of four for 6-volt camera applications? If the camera would tolerate the initial overvoltage (7V instead of 6V with alkaline disposables), it would increase capacity by 25% at a stroke. I suspect many of the external '6V' mains power adapters are poorly regulated anyway.
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Old Aug 7, 2003, 7:43 AM   #6
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Chances are if the cam supply is 6 volt, it's regulating to 5, so I'd try a lower external pack voltage first. Regarding SLA's, the major factor here is the higher self discharge rate if left alone for a few weeks. C and D cells in Nicad/NiMh pack a punch with high peak current output compared to dry cells.

Checkout the peak discharge currents of zinc/carbon lantern batteries. It's usually low and an AA NiMh will outperform in this important area. Don't forget if your camera is loading 0.5-1amp, the peak current (low internal resistance) of the supply is important for digital equipment. For long periods away without access to a charger, Nicads and Alkalines will hold their capacity longer, but capacity for size will be lower.

I'd have thought a genuine Alkaline lantern bat would be ok, but there are some re-chargeables around which just have 4 C cells in the space - Never mind the volts, compare the weight!

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I suspect many of the external '6V' mains power adapters are poorly regulated
Actually, most camera originals are small switchmode units with internal fuses, over voltage protection, continuous rating and superior regulation. The problem is with the cheaper oems that some people use to destroy their cameras!
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Old Aug 13, 2003, 7:00 PM   #7
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Indeed average power adaptors are not regulated into " flat voltage". Although smoothed, there is still a wave form, because they lack a power regulating transistor. Music and computer parts stores do have regulated power adapters/suply.

Or one can build such from a kit available at Radio shack and alike.

Personally I think of simply rebuilding a wind up lantern to charge my Li-Ion batteries. Makes sense when being on the road and running out of juice.
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Old Aug 13, 2003, 8:07 PM   #8
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Steve accessories section has this reference:
http://www.steves-digicams.com/2001_...nimh_pack.html

The full home page:
http://www3.sympatico.ca/akouzmit/Battery_Pack/
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Old Aug 13, 2003, 11:47 PM   #9
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KCan

Thanks for that home bade battery pack link! I had stored one to it ages ago and lost it. Now I've got it again.

Eric
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