[Elecraft] K2 qrp battery drain estimation

[Michael Babineau]

Robert : 

If you are planning to use Lead-Acid technology (SLA or wet-cell )
then, as others have suggested, you should double your calculated capacity, as you never want
to drain a Lead-Acid battery by more than 50% ..

so 

10 hr requires 7 Ah
20 hr requires 15 Ah 
etc.

The reality is that you will probably spend somewhat more than 50% of the time listening and tuning around
for stations when you are S&P so the real split may be more like 30% TX and 70% RX, but 50/50 is probably
a good guess. 

One further point .. don't discharge a Lead acid battery below 10.5 v. Repeatedly doing this will shorten
its lifespan.  Don's suggestion of setting the low voltage indication on the K2 to 11v is a good idea.

For picnic-table-portable operations, battery booster packs (intended to jump-start cars) work very well
and it is easy to find one with an SLA in the 10Ah to 20Ah range, often on sale. You can take the plastic
case apart to install some fusing and even powerpole connectors to customize it for your application
(I also removed the jumper cables from mine).  Some of these packs now even come with USB ports to allow for impromptu 
powering/charging of i-Devices.  It is often cheaper to buy one of these than to purchase just the equivalent capacity SLA
battery .. so you get a nice carrying case with a handle and other goodies for free. 

Best of luck ...

Michael VE3WMB 



>From: Robert G Strickland <rcrgs at verizon.net>
>Date: June 14, 2013 6:28:10 PM EDT
>To: Elecraft <elecraft at mailman.qth.net>
>Subject: [Elecraft] K2 qrp battery drain estimation


>If I'm operating a K2 at 5w cw, in S&P contest mode, I compute the current drain under the stated conditions as follows:

>conditions:
>50% listening, 50% transmitting
>CW 50% duty cycle

>current:
>200ma receive, more or less
>1.0a transmit, more or less

>current draw per hour:
>100ma [30min rcv] + 250ma [30min xmit @ 50% duty cycle] = 350ma per hour

>10Hr requires a 3.5Ahr battery
>20Hr requires a 7.5Ahr battery
>etc...

>Is this more or less accurate, or have I missed something? Thanks.

>...robert
-- 
>Robert G Strickland, PhD ABPH - KE2WY
>rcrgs at verizon.net.usa
>Syracuse, New York, USA