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external Battery - connected to DC-IN

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Offline jetzt

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external Battery - connected to DC-IN
« on: 20 / January / 2008, 04:39:45 »
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Sometimes it's frustrating, you have three pairs of full NIMH-batteries and if they're too warm or too cold,
they don't work any longer.
So I thought about a small voltage-regulator and found this sample circuit:


There is only one problem left: Wich polarity is the DC-IN, on my A710 for example?
Does anybody know?

I know there are more efficient methods, but this one is the smallest and can be used with almost every Battery from
4 to Vmax of voltage-regulator.

 There is only one problem left: Wich polarity is the DC-IN, on my A710 for example?
There is only one problem left: Wich polarity is the DC-IN, on my A710 for example?
 There is only one problem left: Wich polarity is the DC-IN, on my A710 for example?
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Offline kwf

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Re: external Battery - connected to DC-IN
« Reply #1 on: 20 / January / 2008, 12:00:52 »
Well normally outside is negative and the center is positive. But I have already seen it reversed.
Maybe someone owns a ACK800, which would be the compatible AC-DC converter. On ebay i saw some affordable ack800 (probably not original). It is surprisingly powerful 2 A. I wonder why 2 Ampere is needed?
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Offline jetzt

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Re: external Battery - connected to DC-IN
« Reply #2 on: 20 / January / 2008, 12:17:18 »
Hey, thanks, I had alredy serached amazon for pictures, but they all had too low resultion and/or
only upside shown,
now I searched ebay twice and found what I was looking for: :D :D :D :D :D :D
Ebay offer with bottom-side picture in high resultion

It says: minus - ---<.--- + plus
plus inside
minus outside
and 3v -- 2A

but I think these are only absolute maximum ratings, for flash reloding or zooming. ::)

Thanks, for the idea with ebay ;)
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Offline PhyrePhoX

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Re: external Battery - connected to DC-IN
« Reply #3 on: 20 / January / 2008, 15:37:05 »
i got a multipurpose DC that i used for my a620 the other day. it has 1.5 A output. in review mode everything was working fine, but in record mode the cam reported "low battery" and shut off, so 1.5 A wasnt enough. and i didnt even shoot a picture!
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Offline jetzt

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Re: external Battery - connected to DC-IN
« Reply #4 on: 20 / January / 2008, 15:41:43 »
thanks, do you think this circuit with that voltage regulator can do this?
Ok just looked it up:
If Vinput - Voutput is lower than/is 15 V it can give up to 2,2 A.
Which polarity is your ac adapter?
 :D
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Offline kwf

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Re: external Battery - connected to DC-IN
« Reply #5 on: 20 / January / 2008, 15:50:37 »
Quote from: phyrephox on 20 / January / 2008, 15:37:05
i got a multipurpose DC that i used for my a620 the other day. it has 1.5 A output. in review mode everything was working fine, but in record mode the cam reported "low battery" and shut off, so 1.5 A wasnt enough. and i didnt even shoot a picture!
Well on my a570is it asks for 3.15V input voltage, but i somehow doubt that it is so picky about the voltage. Problem with these multi-purpose dc adapters is, they often don't deliver true DC voltage, they sometimes have considerable ripple, have unstable voltage. So its not so easy to say the 1.5A is not enough. Would help to measure current and voltage to find the reason.

Did you try to shoot with flash? I think that could be one of the main loads during record mode.
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Offline kwf

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Re: external Battery - connected to DC-IN
« Reply #6 on: 20 / January / 2008, 16:04:07 »
Quote from: jetzt on 20 / January / 2008, 15:41:43
thanks, do you think this circuit with that voltage regulator can do this?
Ok just looked it up:
If Vinput - Voutput is lower than/is 15 V it can give up to 2,2 A.
Which polarity is your ac adapter?
 :D
Well why not? Its inefficient but should work. Just don't forget a well dimensioned heat sink. I think the LM317 is a linear regulator, 33W heat dissipation at 15V drop and 2.2A...
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Offline PhyrePhoX

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Re: external Battery - connected to DC-IN
« Reply #7 on: 16 / March / 2008, 07:50:46 »
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Offline jetzt

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Re: external Battery - connected to DC-IN
« Reply #8 on: 16 / March / 2008, 08:02:39 »
wow 4.5V my dc-in says 3.15 V, maybe only a difference between models.
Right now I don't have my universal battery-adapter, because my next reichelt order is not full.
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Offline fbonomi

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Re: external Battery - connected to DC-IN
« Reply #9 on: 17 / May / 2008, 13:45:09 »
I have built a similar power system (extrernal battery do DC IN)

I found an extremely cheap LM317-based regulator on ebay.it ( http://cgi.ebay.it/ws/eBayISAPI.dll?ViewItem&rd=1&item=120259405746 ) and I am using it with a small motorbyke battery (12V, 4AH). The regulator is heating quite a lot, and I doubt if the 4AH will last significantly longer than the 2.500 mAh NiMH AA batteries I use.

If the battery is rated 4AH for 12V, how many AH will I get after I regulate it down to 3.7?
Common sense says exaclty the same, but I have the impression I should have a better result...

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