[Elecraft] Re: Field Day Battery Capacity

[David A. Belsley]

Daniel:
  I don't always work the full 24 hours of FD, but I work a lot of them. 
Two 7 aH batteries are more than enough when running 5w.

best wishes,

dave belsley, w1euy

--On Monday, April 28, 2003 5:00 PM -0400 W5EI@cs.com wrote:

> Daniel
>
> If you are using the K2 as a QRP rig, the "jump start" battery might
> work.   Current drain on receive should only be 250 mA or less (your
> mileage may  vary).  The Wal-Mart type battery I have is a 19 amp-hour
> one, so 24 hours on  receive at 250 mA is no problem.  Of course
> transmitting is going to require  1.0 to 2.0 amps if you stay at 5 watts
> or less.  The K2 is rated for 2 amps  at 10 watts.  Duty cycle for CW is
> pretty low, 50% or less.  If you are like  most operators, you will be
> doing more listening than transmitting.  Let's  say you transmit 30% of
> the time.  At the risk of greatly oversimplying  things, here is the way
> I would figure it:
>
> For RX:  24 hrs x 250 mA  x 70% time factor =  4.2 amps
> For TX:  24 hrs x 2.0 amps x 50% duty cycle x 30% time factor = 7.2 amps
>
> The 2 amps I use for the TX current is meant to be conservative figure;
> you  probably won't use that much at 5 watts with a well built K2.  Most
> of the  jump-start gel cell batteries I see in the discount stores are 17
> amp hour  ones.  That much capacity should be adequate unless you
> transmit a lot more  than the scenario I have outlined above.
>
> Good luck,
>
> Don
> K2 #2478
>
>
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----------------------------------
David A. Belsley
Professor of Economics