Rich, you know the C size nimh cells well. Unless
Greg plans to fill up the 40GB drive sitting in
pause with headphone volume up much of the time,
don't you think he could stay up and running with
2- 10X 1.2 volt (10,000 mAh per cell) nimh packs
on the 722 for many days? Would make more room
for your gear on the plane. The 722 is very
challenging to calculate wattage for because
several factors, even the sample rate,
significantly alter the requirements. Rob D.
=3D =3D =3D =3D
At 3:03 PM +0000 9/6/05, 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.=A0
>
>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 =3D 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=A0
>> question:
>>
>> Why use 10 cells for 15 volts when the SD units spec 10 - 18? in the=A0
>> external supply? Is it for longer life as the original voltage is=A0
>> higher? Wouldn't it work as well using the 8 pack at 12V which would
>be=A0
>> a more compact package? Curious if you have tried that and found it=A0
>> lacking... I would think seriously about using 8 cells, building two=A0
>> packs, and leaving one to charge before switching. Unless you'll be
>in=A0
>> the outback for weeks!
>>
>
>
>
>
>
>
>"Microphones are not ears,
>Loudspeakers are not birds,
>A listening room is not nature."
>Klas Strandberg
>Yahoo! Groups Links
>
>
>
>
--
Rob Danielson
Film Department
University of Wisconsin-Milwaukee
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