[Elecraft] KX1 operating time from 6 AA lithiums

[Wayne Burdick]

Hi Steve,

What we say in the manual and FAQ is about 20 hours on one set of lithiums. Of
course this will depend on the type of operation. If like most QRP ops you tune
and listen a lot more than you transmit, you'll be on the high end of the range.
If you're doing constant CQs with auto-repeat, expect a lot less time.

20 hours of operating time represents just about an entire Field Day effort
(with little sleep!). Or perhaps 2 to 3 weeks of backpacking use, operating an
hour or two each day. Or one, 1-hour day-hike operation per week for 6 months.
You get the idea....

Here's how we came up with the 20-hour figure. Average receive current is in the
vicinity of 35 mA. Average transmit current, running 1.5 watts from an internal
8 to 9 V battery, might be around 10 times that (350 mA). Let's say you're
listening around 80% of the time and transmitting 20% (pretty typical for
overall QRP activity). Since CW has about a 50% duty cycle, your actual key-down
duty cycle is around 10%. Simplifying things a bit, the average current drain is
about 35 mA * 0.9 + 350 * 0.1 = 66 mA. The lithium batteries are rated at about
2800 mA-hours, so the number of hours of operating time is 2800/66 = 42. Divide
that by two to be conservative (a good engineering practice) and you get 21
hours. 

Another interesting figure is receive-only operating time: 2800 mA-hours / 35 mA
= 80 hours!

73,
Wayne
N6KR

Steve.Lawrence@ITWFEG.COM wrote:
> 
> Wayne (and other KX1 owners):
> Can you begin to characterize operating time from a set of 6 AA lithium
> batteries?  I know this is difficult as the variables are many, but how
> many evenings operating, about an hour at a time, listening something like
> 80%, might one expect?  (or whatever test conditions have been
> conducted...)
> 
> Have we reached a point in efficiency, that rechargeable batteries and
> solar panels are no longer needed for an outing a week in duration?
> 
> Tnx,
> Steve
> aa8aff