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.=20
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=20
> question:
>
> Why use 10 cells for 15 volts when the SD units spec 10 - 18? in the=20
> external supply? Is it for longer life as the original voltage is=20
> higher? Wouldn't it work as well using the 8 pack at 12V which would
be=20
> a more compact package? Curious if you have tried that and found it=20
> lacking... I would think seriously about using 8 cells, building two=20
> packs, and leaving one to charge before switching. Unless you'll be
in=20
> the outback for weeks!
>
________________________________________________________________________
________________________________________________________________________
|