John, I have been using my K3 (sometimes together with my second one) for FD at 100W for many years with excellent results. The power source is pre-charged lead acid batteries which we change as needed. Sometimes the battery in use is assisted by an ancient solar panel that probably doesn't contribute much. I would roughly say about 3 "full size" batteries are good to power one K3 and a laptop for the whole contest with no solar. The batteries have mostly been the flooded type including 12V types and pairs of 6V golf cart ones wired in series (I count the pair as two full size batteries). My yellow Optima AGM is often used as one of the 3. Starter batteries are not suitable for the deep discharges we are using. True deep cycle batteries are best. Marine batteries are ok but not as good for deep cycling as true deep cycle batteries. It is true that the K3 will work to as low as about 10.5 V, and we have often abused the batteries by letting them go down that far. We tried to check voltage often, but... Eventually one will notice when the radio isn't putting out full power etc. At that point we disconnect and hook up a new battery or 6 V pair. The low voltage performance of the K3 is so much better than some other 12V radios. The K3 is specified to require at least 11V. I have a Yaesu radio that is specified to need at least 11.73V (13.8 V - 15%). One FD we tried an FT-1000MP, which stopped working when only a small fraction of the battery capacity had been used up. With decent batteries and doing only one FD per year, the batteries survive the abuse for several years. Why do I say "abuse" when we use deep cycle batteries for our deep cycling? It is a bit of a myth in ham circles that deep cycle lead acid batteries are made to cycle to almost empty. We get away with it because FD is once a year. The RV industry knows better. Lots of people live in their RV's year around, and may cycle their batteries once a day. A good lead acid deep cycle battery (including flooded or AGM or gel cell) is made to last a few thousand "deep" cycles, but the rule is your "deep" cycle cannot ever discharge below 50% of battery capacity. I can't give good statistical data, but with our abusive but rare use I guess we probably kill a good deep cycle battery in 5 to 10 years. Of course if you make sure never to go below 11 V, you cn probaly get hundreds of cycles. Very roughly I would guess we draw about 200 Ah out of the 3 batteries for the whole contest. Now to your setup with one fully charged 100 Ah batttery and 120 W solar. Solar panels are spec'ed for lab conditions. In practice I would guess your panel delivers about 100W at peak and much less at other times of day. Over the whole day, I would expect to get maybe 500 Wh or about 40 Ah for the whole day. Then consider that a lead acid battery self-throttles the charging current when it is close to full. If in your location the maximum solar radiation occurs near the beginning of the contest, so the battery is almost full, only a small portiion to the current offerd by the solar panel can actually go into the battery, and during receive it cannot go into the rhe radio. So overall you would get much less than 40 Ah our of the solar for the whole day. The battery has 100 Ah, but if I remember correctly, that includes charge deliverable after the battery voltage has dropped a lot, such as below the level where the radio stopped operating (and you are really asking for battery damage). With a wild guess (don't ask me to justify these numbers) if you run the K3 like we do, with your setup you might have only 80 Ah available from the one battery and 20 Ah from the solar panel, for a total of 100 Ah, which is half of the 200 Ah needed.
73, Erik K7TV -----Original Message----- From: elecraft-boun...@mailman.qth.net <elecraft-boun...@mailman.qth.net> On Behalf Of Bill Frantz Sent: Wednesday, May 27, 2020 6:13 PM To: John Kountz <j...@t6ee.com> Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] RE; How well does the K3 work with lower power supply voltage . . . When our club, the West Valley Amateur Radio Association, does field day, we use many K3 and Flex transceivers. We run them from 12 volt lead-acid batteries with solar power systems to top up the batteries. We have had not had any significant problems in any of SSB, CW, or Digital, although I think the the digital stations have the heaviest battery drain. We have noticed that before dawn, when the batteries are getting low, the IMD increases and we get more QRM from other stations in our operation. Swapping in a fresh battery always cures the problem. Note that we run QRP, which helps with avoiding intra-station QRM and boosts the score. If I were buying batteries for portable/field operation today, I would look at the Bioenno LiFePO4 batteries. Good power/weight and power/size ratios and near full voltage until the end of their capacity. The down side is they are more expensive the lead-acid batteries. 73 Bill AE6JV On 5/28/20 at 8:41 PM, j...@t6ee.com (John Kountz) wrote: >I have two K3 transceivers and have attempted to use them on several >Field Days with limited joy and unlimited disappointment. I've >attempted to use one or the other with >120 Watt solar cells and 100 AH GelCel and/or Lead Acid batteries which >had been charged beforehand. As long as there is healthy sunlight and >you have a duty cycle of between 10 and >15 percent transmission with 85 to 90 >percent monitoring you'll have a functioning station. ----------------------------------------------------------------------- Bill Frantz | Ham radio contesting is a | Periwinkle (408)348-7900 | contact sport. | 150 Rivermead Rd #235 www.pwpconsult.com | --Ken Widelitz K6LA/VY2TT | Peterborough, NH 03458 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to ebasil...@cox.net ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
