Rich
You are invited next spring..
It is incredibly quiet up there, not even bush planes.
Greg Rademacher
On Sep 6, 2005, at 10:03 AM, Rich Peet wrote:
> You do get a longer life out of the 10 cells.
>
> The unit of measure for the life of a battery in this case is a "Watt
> hour" or the number of watts that a battery can put out in an hour
> before going dead.
> Each cell capacity is rated at "milliamp hours" of capacity before
> death so this value times the total voltage gives you "watt hours".
> Then it is easy to look up how many watts the recorder uses and you
> can
> project the life of the battery.
>
> Also in consideration is how the battery ages in voltage sag as it is
> used. Design must stay above the min voltage requirement as long as
> possible as the battery discharges. This far outweighs the very slight
> decrease in effeciency by overvoltage losses at the voltage regulator
> in the recorder. This is seen in the recorder as the voltage regulator
> chip runs a bit warmer.
>
> Now in car batteries where all cars are the same voltage the unit of
> battery life is just discussed as an "Amp hour". This is the number of
> amps that a battery can put out for an hour before going dead. Because
> laptop computers and variable voltage devices like the 722 use many
> different voltages of batteries the preferred method of discussion is
> in "watt hours". This makes it much easier to evaluate.
>
> So in review, my mic preamp uses 4 watts and has a variable voltage
> supply. I can power it with either dc or ac over a wide range. In the
> field I use a 12 volt, 5 amp hour battery. 12 X 5 = 60 watt hours / 4
> watts giving the expected life on a single charge at 15 hours.
>
> This also makes it clear that Gregs best solution for his week in
> Canada is simple. He needs to invite me to carry his batterys.
>
> Rich
>
>
> --- In Lou Judson <>
> wrote:
> > All this battery info is great, against future need for me. But a
> > question:
> >
> > Why use 10 cells for 15 volts when the SD units spec 10 - 18? in the
> > external supply? Is it for longer life as the original voltage is
> > higher? Wouldn't it work as well using the 8 pack at 12V which would
> be
> > a more compact package? Curious if you have tried that and found it
> > lacking... I would think seriously about using 8 cells, building two
> > packs, and leaving one to charge before switching. Unless you'll be
> in
> > the outback for weeks!
> >
>
>
>
>
>
> "Microphones are not ears,
> Loudspeakers are not birds,
> A listening room is not nature."
> Klas Strandberg
>
>
>
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________________________________________________________________________
________________________________________________________________________
"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
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