7.2v / 8.4v Confusion

Archived from groups: rec.photo.digital (More info?)

Ken Zenachon <spamaddy1@yahoo.com> writes:
> My Nikon Coolpix 4500 (and yours, too, I'd presume) accepts EN-EL1
> batteries which output 7.2v DC (the equivalent of six 1.2v NiMH cells).

That would mean two li ion cells (18500 or whatever) which are 3.6 volts
nominal, 4.2 volts at charge completion.

> That's fair enough, but why, then, does the little rubber cover on the
> DC terminal prompt me for a DC input of 8.4v (or the equivalent of
> seven 1.2v NimH AAs)?

Who knows? The dc input is not necessarily the same as the battery
voltage, especially in devices that charge the batteries internally.

> If I feed it 7.2 volts will it starve?

Probably not, but if it asks for 8.4, I'd say give it 8.4.

Archived from groups: rec.photo.digital (More info?)

Ah, so will the camera operate without a battery if there's DC at the
external port?

KZ


On Mon, 09 May 2005 03:39:27 GMT, "Marten" <surreymicro@hotmail.com>
wrote:

>A voltage higher than the battery pack is required to force electrons into
>the battery in order to charge it. If you feed it 7.2 volts it will not be
>able to charge the battery. A volt or so higher will not hurt anything
>because the camera has a voltage regulator inside. The electronics in the
>camera probably run on 5 VDC or less.
>
>Marten
>
>"Ken Zenachon" <spamaddy1@yahoo.com> wrote in message
>news:lfkt71ppc68464kp2h07g29ta0hvcncjeh@4ax.com...
>> My Nikon Coolpix 4500 (and yours, too, I'd presume) accepts EN-EL1
>> batteries which output 7.2v DC (the equivalent of six 1.2v NiMH
>> cells).
>> That's fair enough, but why, then, does the little rubber cover on the
>> DC terminal prompt me for a DC input of 8.4v (or the equivalent of
>> seven 1.2v NimH AAs)? If I feed it 7.2 volts will it starve?
>>
>> KZ
>

Archived from groups: rec.photo.digital (More info?)

On Sun, 08 May 2005 22:59:37 -0400, Ken Zenachon wrote:

> My Nikon Coolpix 4500 (and yours, too, I'd presume) accepts EN-EL1
> batteries which output 7.2v DC (the equivalent of six 1.2v NiMH
> cells).
> That's fair enough, but why, then, does the little rubber cover on the
> DC terminal prompt me for a DC input of 8.4v (or the equivalent of
> seven 1.2v NimH AAs)? If I feed it 7.2 volts will it starve?

You aren't aware of how NiMH batteries work. When fully charged
they might provide a bit more than 1.2 volts per cell, but just
before they are fully depleted, they are providing a bit more than
1.0 volts. Whether your camera might still be operable when only
provided with a little more than 6.0 volts I can't say, but it has
to be able to operate fairly close to 6.0 volts or it wouldn't be
able to use most of the energy in the batteries, and battery life
would be fairly short. Just a guess, but I suspect the camera
should be able to operate over the range of 5.5 to 8.0 volts.

In any case, to more fully answer your question it would be nice
to know if the DC input is used to power the camera, charge the
internal battery or both? The input is probably diode protected to
prevent damage by plugging in a power supply with reversed polarity.
That alone would drop the 8.4 volts to about 7.7 volts if a silicon
diode is used. If the DC supply is used to charge the internal
battery, it would have to provide a higher voltage than that of the
battery, unless a more complex, voltage boosting circuit was used.

If the DC input is used to operate the camera, 7.2 volts fed to
the DC input might allow it to operate nicely, but go for a higher
voltage if you can. But if the DC input is used to charge the
battery, it might not be able to charge the battery to its full
capacity, or if it does, might take longer to do so. But it
shouldn't "starve" or harm the camera.

Archived from groups: rec.photo.digital (More info?)

Ken Zenachon <spamaddy1@yahoo.com> wrote:
: >> If I feed it 7.2 volts will it starve?
: >
: >Probably not, but if it asks for 8.4, I'd say give it 8.4.

: That makes sense, but I noticed, today, that while most popular
: battery packs on the market today are designed to be connected through
: the external DC terminal, they still output 7.2v, which makes me
: believe that the power requirements for these camera thingies are
: *very* flexible.

The 7.2, in this case, would be enough to power the camera but charging
batteries from a battery pack is probably not recommended. A voltage of
8.4 may be required to charge the batteries while the camera itself only
requires 5v. but instead of listing two voltages in the limited space on
the camera body, they only list the full voltage needed. IMHO

I don't know specifically about cameras, but many electical operated items
have a voltage regulator in the DC in line that works best if the input
voltage is well above the output voltage. This means that minor variations
in voltage (from a ac-dc power supply) will be smoothed out before the
output. This way an AC supply with slight voltage variation (ac hum) or an
external battery pack that looses voltage over use time, will still power
the camera in an acceptable manner. If you supply a batttery that only
outputs the minimum acceptable voltage for the first 10 min of use, it
would be unusable. But an 8.4 pack that does not drop to 7.2 for over a
couple of hours of continuous use will be very helpful. And if the camera
requires only 5v to run (without any battery charging) the battery pack
could theoretically power the camera for a full day of continuous use.

JMHO

Randy

==========
Randy Berbaum
Champaign, IL

Archived from groups: rec.photo.digital (More info?)

Ken Zenachon <spamaddy1@yahoo.com> wrote:

>My Nikon Coolpix 4500 (and yours, too, I'd presume) accepts EN-EL1
>batteries which output 7.2v DC (the equivalent of six 1.2v NiMH
>cells).
>That's fair enough, but why, then, does the little rubber cover on the
>DC terminal prompt me for a DC input of 8.4v (or the equivalent of
>seven 1.2v NimH AAs)? If I feed it 7.2 volts will it starve?
>

>KZ

Likely to have enough potential to actually charge battery since it
has internal resistance and I have a feeling that there is reverse
polarity protection (diode) that will drop .6 volts or so plus some
kind of regulation circuit to tailor charge currents to batteries
liking.

Wes

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