For a K2 or K3, using 2 amps as a reasonable current drain on TX and 50% duty cycle. Operating for a 24 hour period - 12h will be on TX. A safe bet will be to have a 20Watt panel keeping a 30amp-hour SLA reasonably topped up for night time operation allowing for a 15 a-h drain maximum will get you 7.5h of TX time. Better to have more and not need it than otherwise. That will be my set-up for Field Day using a KX3. Since the current drain on a KX3 is lower than that of a K2 or a KX3 on TX and RX, approximately 1 amp on TX, I could probably get by without a solar panel with a 30 a-h SLA or use 15a-h with a panel. For a K2 or K3 in QRP mode I would go the full 30 -h SLA and a panel. In the above, overestimating the duty cycle approximates the receive duty since that was not explicitly calculated.
More accurately: K2 or K3 Outflow = 12h(2 amps) + 12h(0.2 amps) = 26.4 a-h Inflow = 12h*50%efficiency*1 amp = 6 amp-h Net Outflow ~ 20 amp hr Need 40 a-h battery with a 20w panel So if the TX duty cycle is lower than 50% - you might be able to get by with a 30 a-h battery with a panel KX3 Outflow = 12h(1 amps) + 12h(0.15 amps) = 13.8 a-h Inflow = 12h*50%efficiency*1 amp = 6 a-h Net Outflow ~ 7.8 a-h Need 16 a-h with a panel or 30 a-h battery without a panel Ariel NY4G Sent from my iPad On Jun 15, 2013, at 10:15 AM, "Philip Townsend Lontz" <[email protected]> wrote: > > So, for Field Day running CW only any ideas about what the required amp hours > will be? > > Sent from my iPad > > On Jun 15, 2013, at 8:06 AM, Michael Babineau <[email protected]> wrote: > >> 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 <[email protected]> >>> Date: June 14, 2013 6:28:10 PM EDT >>> To: Elecraft <[email protected]> >>> 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 >>> [email protected] >>> Syracuse, New York, USA >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
