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Old Apr 2, 2005, 2:38 AM   #1
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I have built an external battery power source using a holder for 4x AAA alkaline batteries, a DC power connector which connects to the DC power socket on camera and a 1 meter connection wire between them. (so that I can leave the power unit in my pocket).

This provides 6.23 volts.

This will be useful for long outings away from standard power sources. (I need it for my next trip later this month).

It is fortunate that the A200 seems to have a fail-safe power cutout. It appearsx that the voltage output from my unit is too high. This unit described above does not work. Yes, the polarity is correct.

My off-the-shelf mains power transformer provides 6.03volts and works with the A200 perfectly well.

I assume that I will need a Zena diode or some alternative voltage controller in order to cut the voltage to about 6volts.

What electronic component will I need to restrict the voltage to 6v and how should it be installed?

Maurice
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Old Apr 2, 2005, 3:42 AM   #2
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Something's not right here bacs57. Apart from the fact your 4x AAA pack is not working, the performance & capacity of that pack will not be very adequate.

The camera internal battery is a 7.2v 800mAh Lithium-ion rechargeable. What makes you think the camera has a "fail safe power cutout" ? If so, it would seem unlikely to cutout at 6.23volts. How did you measure the 6.23v ? I imagine that is the "open circuit" voltage, but the voltage will drop a little when loaded by the camera.

But the pack does not work. Is the small plug on your connection wire the exact correct one for the camera socket? They come in different sizes. Or possibly are the AAA cells inadequate for powering the A200? Steve recommends avoiding alkaline cells for digi cameras. Better to use Li-ion or NiMh rechargeables.

Another thought, is to get the Minolta external battery pack kit, EPB-100. This can be fitted with an even higher capacity Lithium-ion battery than the NP-800 in the camera.

Good luck.
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Old Apr 2, 2005, 4:46 PM   #3
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The NP800 is labelled 7.4v 800mAh. Since my mains transformer power source feeds the A200 with 6v output successfully, I had assumed that 6v was sufficient.

Your are correct since I am using a multimeter to read off the voltage and this will change with load applied.

I have 1x NP800 and 2x EN-EL1 700mAh batteries. I expect that these will expire after 3 days in the jungle with no electric power source. The alkaline power unit is just a back-up for this particular ocassion. The advantages are (a) cost; (b) weights; (c) availablility of AAA alkaline batteries; (d) complete independence from mains power.

It seems that I need to boost the output of the power unit from 6 to 7.5v for this to work.

Thoughts?

Maurice
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Old Apr 2, 2005, 4:48 PM   #4
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By the way. The plug connector is the correct size and definitely makes the connection.
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Old Apr 3, 2005, 4:38 AM   #5
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What a turn arround bacs57! Yesterday you asked how to reduce your aaa pack from 6.23 to 6volts.
And now today you ask how to boost the aaa pack from 6 to 7.5 volts?

I dont have the A200 camera, but I can see from the specs, it is an excellent camera. Why are you messsing with an inadequate aaa power source.

The advantages you list are valid. But have you considered the disadvantages? Like very limited capacity & performance of aaa alkalines?

"By the way. The plug connector is the correct size and definitely makes the connection." How do you know? As the aaa pack has never worked with that plug.

Well my friend, I am not being critical, but trying to help. Apart from voltage, there is current to consider. Modern camera's require considerable current to operate.

Possibly the aaa wont provide the current required for your camera. Maybe thats why they dont work.

And so, good luck.. lets know how you solve this one..



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Old Apr 3, 2005, 4:48 AM   #6
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bacs57 wrote:
Quote:
It seems that I need to boost the output of the power unit from 6 to 7.5v for this to work.
Won't work... literally never!

Without load voltage of alkalines is 1.5V meaning 6V total.
But alkalines can't handle heavy loads which literally causes crash down of voltage... (remember how 7-serie worked, or actually didn't work with alkalines)
And now you're using triple-As which are even yet prone to high current.

You might get it working with AAs, remember that battery grip for A1/A2 can use two NP-400s or SIX AAs.

But even then I wouldn't keep it as good alternative (operating time would be short) and with ordinary battery pack for six AAs you would have TWELVE bad contacs so if one contact adds say 0.1 ohms it means total resistance of 1.2 ohms.
With 1 ampere current that would mean 1.2 V voltage loss!
And that is just to top of already crashing down voltage of alkalines with this kind of loads.

If you want better durability than "ten" shots C-cells would be only choise.
Or other choise would be to put say two, three "packs" of six AAs in parallel to lower load for individual cells.
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Old Apr 3, 2005, 8:21 AM   #7
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Thank you Baz and E.T. This has given me a lot to think about.

I was at first optimistic because I have been using a similar home-made alkaline power pack based on the square 9v battery for my Digital Wallet, and with good success over a long period (although I have now purchased a new internal battery pack to fill the cavity).

It seems that I will not have this power unit up an running for my next trip. I will have to survive 4 days in the amazon jungle with my 3 NP800/EN-EL1 batts without electric supply. This will probably mean a lot of manual focus and selective shooting. Also without flash. I might have to recommission myaged film backup camera.

Maurice


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Old Apr 3, 2005, 9:42 AM   #8
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You might want to check this:
http://www.network54.com/Forum/messa...eid=1087120519
Or directly:
http://www.jr-worldwi.de/photo/index...age_power.html
While those aren't/doesn't use disposable (and buy from everywhere) alkalines their price is definitely magnitude lower than KM's own batterypack and they have quite nice capacity. (about 4xA200's internal battery for NiMH-packs)


Or some self made:
http://www3.sympatico.ca/akouzmit/Ba...Pack/index.htm


http://www.network54.com/Forum/messa...eid=1111703957
Also check next messages... those 10Ah backs are little heavier (~1 kg) but with them you could power camera very long.


BTW, dimensions for power plug are ~4mm outside diameter and ~1.7mm for hole.
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Old Apr 3, 2005, 10:29 AM   #9
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This might work with better alkalines.

http://home.tiscali.nl/~t800373/power.htm

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