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[aprssig] Backpack Portable Battery Specs

Wes Johnston, AI4PX wes at ai4px.com
Tue Feb 26 14:13:23 UTC 2008


kpc3 draws about 14ma with lights off, not bad at all!
typical mobile radio draws 1.4amps rx, 12 on TX if hi power, 5amps if low
power.

you need to figure out your ratio of RX to TX.... let's say it's once every
3 minutes.  That is 1 second  tx (give or take TXDelay) and 179sec rx,
spread over an hour.  Your radio will spend all but 20 seconds in receive
mode.... 59.6 minutes in receive... or 99.3%.  The0 .7% of the time is spent
in TX mode at high current draw.


TX mode= .007 x (12.014A) = .084Ah
Rx mode= .993 x (1.414A) =  1.404Ah
total power is 1.488Ah.

If you use a HT w/o battery saver, count on .3 amp for RX and 1.5amp for TX
 TX mode= .007 x (1.514A) = .011Ah
Rx mode= .993 x (0.314A) =  0.310Ah
total power is .320Ah.

By using an HT, you realize a 4½ increase in operating time.  Note that most
of the power budget is spend running the reciever.

If you plan ot use this setup with a private, temporary network, you can use
the AXHANG parameter of the digipeater and make it have a really long TXD on
an initial transmission and a normal TXD on subsequent transmissions.  You'd
need to set the drop time (can't remember parm) to the sleep time of your HT
rx draw will drop to .03amp over all.

Wes

On 2/26/08, Ev Tupis <w2ev at yahoo.com> wrote:
>
> I'm thinking about "backpack portable" operation with
> a full-blown TNC/transceiver(.  I'm figuring the draw
> to average 2 amp-hours, but haven't decided just how
> long to need that draw.
>
> Before I go considering choices, I wonder if anyone
> on-list has any experience with "backpack portable
> friendly batteries/configurations" and would care to
> comment on their trials/tribulations/successes?
>
> Regards,
> Ev, W2EV
>
>
>
>
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