Solar Power
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Guys and Gals of the K3 ilk,
I am interested in setting up my K3 to run off of solar power but know very little about what it will take. I assume a battery and a controller/charger but what size battery would work best for operation up to 10 watts, and what would work best up to 100 watts (occasionally!) (and I do not need 120 pound flooded lead acid batteries -- lighter weight, gelled cells in the 60 pound range are preferable -- my back is not what it used to be!) Charging off the grid is acceptable at first, but the idea is to switch over to the solar panel (what size, capacity?) as soon as I can. I am familiar with solar power as I have had, in the past, solar panels charging batteries for some of the house current (running through inverters), although presently I only send the power back into the grid without battery backup. Who out there is doing this for emergency or regular use with the K3 and can offer some assistance? Bill, W4ISH ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Hi Bill,
The K1/2/3 rigs do very well on solar power. We ran the K3 (at 90W) on solar for awhile last Field Day. You are correct in assuming three components for solar: the PV (photo-voltaic) panel, (a constant current source), the storage battery (constant voltage source) and an interface between the two - the charge controller. It remains only to determine the "size" for each component by doing a rough estimate energy budget. For example, the K3 draws about 1 A on receive and about 3 A on transmit (at the 10W setting). If you're transmitting 25 percent of the time (a lot....) and a 50 percent duty cycle (CW/SSB), figure about 1.5 A continuous at 13V (an average battery voltage) or 20 W continuous. A 15 AH (Ampere-Hour) battery would be good for about 10 hours from a full charge. (Theoretically - but more like 7 to 8 hours). But, how about maintaining the battery charge with a PV? Well, of course, an ideal 20W panel would work, but, unfortunately, the panels are not ideal. They don't work at night - that's a (again, roughly) 50 percent loss. They don't work very well in the shade either, and the sun must be perpendicular to the panel for maximum output. Figure another 50 percent loss - we are going to need, roughly, an 80W panel to maintain the battery indefinitely. Another "but", this assumes the K3 will operate around the clock - not very likely - so a 20 W panel and 15 AH battery would be adequate, after all, for casual operating at the 10 W level - without discharging - the battery. This gives us a "feel" for the numbers. This also specifies the required current for the charge controller - 1.5 A, (make that 3 A for cooler running). So: a 20W panel, a 15 AH battery, and a 3A controller would comprise a conservative system for the K3/10. Of course, these numbers can be scaled down if you don't mind discharging the battery over a given number of hours (left as an exercise for the student....). Here at RadioRanch, we are using four 16 AH deep cycle batteries from Wal-Mart, in parallel, on an 80 W panel, with a 12 A controller. This seems to suffice for casual operation of the K3 at 90 W. The batteries are small and light enough to be easily carted about for portable operation. Good luck with the solar.... Rob, N6VX ----- Original Message ----- From: "William Evans" <[hidden email]> To: <[hidden email]> Sent: Friday, September 11, 2009 8:01 AM Subject: [Elecraft] [K3] Solar Power > Guys and Gals of the K3 ilk, > I am interested in setting up my K3 to run off of solar power but know > very little about what it will take. I assume a battery and a > controller/charger but what size battery would work best for operation > up to 10 watts, and what would work best up to 100 watts > (occasionally!) (and I do not need 120 pound flooded lead acid > batteries -- lighter weight, gelled cells in the 60 pound range are > preferable -- my back is not what it used to be!) > > Charging off the grid is acceptable at first, but the idea is to > switch over to the solar panel (what size, capacity?) as soon as I > can. I am familiar with solar power as I have had, in the past, solar > panels charging batteries for some of the house current (running > through inverters), although presently I only send the power back into > the grid without battery backup. Who out there is doing this for > emergency or regular use with the K3 and can offer some assistance? > > Bill, W4ISH > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by w4ish
Hi William,
K3 #24 has been running on solar power since I bought it. Our house electrical is set up a bit like yours, though we have a 48V system and FLA storage that covers the house if grid power disappears. The grid tied inverter is an older Xantrex SW4048. I added 2x 50W Siemens SR50 panels to the roof a little while after the main PV system was grid-tied back in 2002. That's a 12V system, nameplate-rated at 100W. The PV feed comes off the two panels to the radio room here on the second floor and is fused at 10A where is enters the radio room. That feed goes into a Micro M+ charge controller set to 13.56V to charge the SLA (lead-acid, sealed) battery. The battery is nameplate-rated at 110AH. All radio equipment runs off the SLA battery (K3, K2, scanner, even an inverter for 400W @ 120VAC). I'd say you can get away with < 50W of PV, and use the Micro M+ or eqiuvalent. The M+ is good for about 8 Amps if you upgrade the output FET. A 50 - 80AH AGM type battery will probably just about cut it if you're operating < 20W. Most of my ops are in that range, and I've found the 110AH battery is a wee bit of overkill most of the time (but very good for cloudy weather). You may also use the charge controller off a regular AC to DC power supply to charge the battery when solar isn't available or if needed for high duty cycle ops like contesting. I do this sometimes for those reasons. The Micro M+ charge controller is good for less than +14.5V out of the power supply because it behaves like an LDO regulator. Low voltage drops don't bother it. Good Luck and 73, matt zilmer W6NIA K3 #24 On Fri, 11 Sep 2009 08:01:47 -0400, you wrote: >Guys and Gals of the K3 ilk, >I am interested in setting up my K3 to run off of solar power but know >very little about what it will take. I assume a battery and a >controller/charger but what size battery would work best for operation >up to 10 watts, and what would work best up to 100 watts >(occasionally!) (and I do not need 120 pound flooded lead acid >batteries -- lighter weight, gelled cells in the 60 pound range are >preferable -- my back is not what it used to be!) > >Charging off the grid is acceptable at first, but the idea is to >switch over to the solar panel (what size, capacity?) as soon as I >can. I am familiar with solar power as I have had, in the past, solar >panels charging batteries for some of the house current (running >through inverters), although presently I only send the power back into >the grid without battery backup. Who out there is doing this for >emergency or regular use with the K3 and can offer some assistance? > >Bill, W4ISH > > >______________________________________________________________ >Elecraft mailing list >Home: http://mailman.qth.net/mailman/listinfo/elecraft >Help: http://mailman.qth.net/mmfaq.htm >Post: mailto:[hidden email] > >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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Solar power works great and now with the 30% tax incentive you have a
real decent pay back. However there a some downsides! Remember that PV panels have a lot of wind surface and there could be zoning considerations and of course you need to face south and being at the roof angle you lose a lot of potential production. At a home installation changing the angle about 4 times a year will really increase your production if you can find a spot with a clear look to the south. Here in the north country really the crucial time is Dec and Jan so I just set them for maximum efficiency for those two months but it would be a different story to the south. I have four 205 watt 24 volt panels and eight 150 AH batteries and an Outback Flex 80 MPPT controller. I run everything on 12 vdc in the radio room as well as emergency lighting. I plan to add a sine wave inverter to run the computer, DSL modem and router and a couple of rotors. For me the biggest downside to solar power is RFI which is commonly generated by the controller and radiated by the wiring from the panels and wiring to the batteries. Another big noise problem with solar power can be the inverter. However since the K3 runs on DC and a lot of things in the radio room runs on 12 vdc you can make a lot of use of the PV system without an inverter. If you need an inverter then you are going to need a true sine wave one and even then you might have RFI so be sure and buy one that hams have had good success with. I use a MPPT solar controller, Outback Flex 80, and it puts out "birdies" approximately every 24 khz when the controller is active. They are loud and can be heard for several 100 feet. Of course one can work around these birdies since they are every 24 khz and/or shutting off the panels cures the RFI. One can charge the batteries when not operating. Of course more battery capacity give you more flexablilty in this regard. The birdies are on AM broadcast through two meters. Of course when the controller is "sleeping" there is no problem. The birdies do move some in frequency. So far they have not ended up on a place I monitor but if they do then the problem is much more serious. An example would be 50.125 or 144.200 or 14.195, etc. I hope to do some more work to try and get rid of the birdies but I suspect it is not going to be easy. So far twisting the wires to the batteries and ferrite do nothing so I am going to have to try by passing and more shielding. PV systems and inverters do not seem to be regulated by the FCC as to noise generation. It is possible that the non-MPPT controllers are much cleaner and given a couple posts here have not mentioned the RFI problem and they did not use MPPT controllers they probably are. For a PV system you definitely do not need a MPPT controller so that is definitely something to check out. Another important thing is if you are "NOT" using lead acid batteries where you can add water be sure and be careful not to run to high a float voltage. These batteries are very easy to ruin by doing this. Obviously with the ones you can add water you still have to be sure to watch the water level and should run the proper float voltage! Also do your very best to not discharge your batteries more than 50% and better yet as much as possible try not to go below 80% and if you watch the water level and float voltage on average batteries will last a long time. I have 16 SAM's Club golf cart 6 vdc batteries that I use for my 5th wheel and are in a battery box in the box of the F-350 and are charged by a second alternator and are now going on 9 years. I just checked them today and the resting voltage was 12.6 volts which is excellent for batteries this old. They are equalized twice a year. Your pay-back on a solar system will be a lot longer if you end up with a short battery life as batteries keep getting more expensive. They are nearly twice what I paid 9 years ago. Ed W0SD No virus found in this outgoing message. Checked by AVG - www.avg.com Version: 8.5.409 / Virus Database: 270.13.93/2365 - Release Date: 09/12/09 06:37:00 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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--- On Sat, 9/12/09, W0SD Ed Gray <[hidden email]> wrote: From: W0SD Ed Gray <[hidden email]> Subject: Re: [Elecraft] [K3] Solar Power To: [hidden email] Date: Saturday, September 12, 2009, 5:45 PM Solar power works great and now with the 30% tax incentive you have a real decent pay back. Absolutely nothing personal Ed, but even living here in sunny Tucson where there is a constant drone from the greenies to "go solar" and lots of self-congratulatory back patting from those who do, the “economic payback” accrues to those who buy the systems with somebody else's (tax) money. I wish those who think solar is the ticket for them would pay for the systems themselves, then we could see how viable this stuff really is. I repeat, nothing personal, just a pet peeve. Regards, Wes ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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