Solar Show and Tell

[AirMiles]

Let’s get back to some Solar Show and Tell. This weekend was my first opportunity to use my 600W of solar on the factory prewire. I chose a mostly tree filled location to really give it a test in a challenging location. As expected, the system struggled in this location, but still produced 500 to 700Wh per day. The system could not get out of bulk mode and maximum Production was in the mid-200W area. Still not bad for only getting 1 hour of possible direct sunlight. Here’s the picture documentation:

[pcskier]

Day 9 on this trip with no need for generator! All three sites were partly shaded to varying degrees, and the last two days were completely socked in and rain, 30s at night. See pic. My 400 watts kept me in business. Amazing. I used the furnace for several hours each night at a comfortable temp, as well as the inverter/tv/dvd to watch a movie. Slept with furnace at 50 or 55 which is fine for me. I’m amazed after the last two days’ foul weather I still produced enough power for my needs.

Q: yesterday was 550 wh. Does this translate to 46 ah pumped in to the 220 ah batteries, at least ‘mathematically’? I think I have that right.
Partial sun today so the panels should crank pretty well. (The 30-day production is a combination of days in the driveway, and two trips—not 30 days in a row. Trailer was in dark storage for a couple periods of time.)

[AirMiles]

Originally Posted by pcskier

Day 9 on this trip with no need for generator! All three sites were partly shaded to varying degrees, and the last two days were completely socked in and rain, 30s at night. See pic. My 400 watts kept me in business. Amazing. I used the furnace for several hours each night at a comfortable temp, as well as the inverter/tv/dvd to watch a movie. Slept with furnace at 50 or 55 which is fine for me. I’m amazed after the last two days’ foul weather I still produced enough power for my needs.

Q: yesterday was 550 wh. Does this translate to 46 ah pumped in to the 220 ah batteries? I think I have that right.
Partial sun today so the panels should crank pretty well.
Attachment 352735Attachment 352736Attachment 352737Attachment 352738

Thanks for sharing PC! I love using my solar powered Airstream! Do you divide Watts by Volts to calculate Amps? Kind of. I usually divide by 13.5V instead of 12V because there is resistance in the process of charging the batteries. On average, the charger is at 13.5V when charging. Sometimes above, sometimes below. Therefore 13.5V is the number I use in that calculation.

I haven’t used my generator for battery charging in over a year of solar Airstreaming. I carry a generator mostly for A/C, microwave and air compressor use while dry camping. I disconnect my 120V charger so I only charge with solar. It’s really great to never need shore power. It allows me to travel anywhere anytime without reservations. Non-electric campsites are much easier to find as there is not as much demand. Enjoy your solar-powered Airstream!

[uncle_bob]

Hi

The solar figures the watts at whatever voltage the battery is getting. If it's boosted up to 14.4V then it will be amps times 14.4V. If you are discharging, you may well have your batteries down around 12.6V. All batteries work this way to some extent.

If you happen to be sitting at 34F and have lead acid's your battery capacity is a bit lower than it would be at 70F. How much depends on just what's in your batteries ( = there are different alloys and chemistry tricks). 30% is a pretty good bet, it might be a bit more. That's on top of the voltage changes that happen with temperature.

So where is this going ....

Well, the *voltage* on a cold lead acid goes up with temperature. The *capacity* (in amp hours) goes down. The combo of the two means that the watts in the battery are not quite as badly impacted as the capacity numbers would suggest ....

Looks like the fog has lifted enough for the sun to hit the panels ....

Bob

[ghaynes755]

Airmiles do another test with your refrigerator. When it is trying to cool then you will get the amp draw that you saw. But most refrigerators don't 'run' 24x7. They cycle on and off. I don't know if Dometic publishes the yellow energy sticker information for their units. But sometime when you aren't camping, get the the fridge to temperature and then monitor your usage with only the fridge running over 24 hours. I'd guess that you may be in the 10-20% range of the 300+ amps you calculated for running all the time.

[AirMiles]

Originally Posted by ghaynes755

Airmiles do another test with your refrigerator. When it is trying to cool then you will get the amp draw that you saw. But most refrigerators don't 'run' 24x7. They cycle on and off. I don't know if Dometic publishes the yellow energy sticker information for their units. But sometime when you aren't camping, get the the fridge to temperature and then monitor your usage with only the fridge running over 24 hours. I'd guess that you may be in the 10-20% range of the 300+ amps you calculated for running all the time.

I did some testing this weekend and today starting with a cold refrigerator, although both tests were done in nearly complete tree canopy. The refrigerator was on DC from 10AM to 7PM. Batteries were already down (at 12.4V) from prior day of tree canopy and overnight usage. The batteries were still at 12.1V at 7PM after powering the refrigerator on DC. I was satisfied with a 0.3V drop over 9 hours. That gives me hope that there is a chance to run the refrigerator for 24 hours with good solar conditions. Temperatures were about 90 degrees, but I had electric so the A/C was on and set at 74 degrees which would help. I had the WFCO converter turned off (12V charging only by solar). More testing to come.

[youngpeck]

I have an Isotherm Cruise 200 fridge that runs on 12v or 110v. I have 470 watts of solar and Lifeline 300-amphour AGMs. The fridge pulls about 7 amps while running. I figure it runs about 50% of the time. Over 24 hours that's a total of 84 amps pulled out of the AGMs. This is by far the biggest draw on the batteries--all lights are LED, and we use a catalytic heater. With 150 amp hours "usable" in the batteries, and reasonably normal sun exposure for recharging, we are doing just fine.

[AirMiles]

Originally Posted by youngpeck

I have an Isotherm Cruise 200 fridge that runs on 12v or 110v. I have 470 watts of solar and Lifeline 300-amphour AGMs. The fridge pulls about 7 amps while running. I figure it runs about 50% of the time. Over 24 hours that's a total of 84 amps pulled out of the AGMs. This is by far the biggest draw on the batteries--all lights are LED, and we use a catalytic heater. With 150 amp hours "usable" in the batteries, and reasonably normal sun exposure for recharging, we are doing just fine.

Thanks for sharing your experience with your refrigerator on solar. I like having enough solar to recharge the usable battery amp hours on a good day of solar production. That way, I can use some of the battery storage on a bad solar day, or two, then recover on one good day of solar production. That appears to be what you are doing and its how my 400W solar system worked with 230AH of batteries.

Now that I have 600W of solar and still only 230AH of batteries, I probably have excess solar production. Maybe the excess solar production can power the refrigerator during the day while replacing the battery amp hours used the prior night. I just don't know if 230AH of batteries can power the refrigerator plus my other overnight overnight needs. Even if it can, how often will I run out of battery storage when the next day is overcast? If powering the refrigerator on DC causes me to run the generator frequently, it would be more efficient to just continue to use propane to power the refrigerator.

We will be finding out the answers to these questions shortly. I plan to leave Friday for up to five weeks of dry camping in the Blue Ridge Mountains. This will provide plenty of opportunity to test my solar setup and determine its capabilities. I will be posting the results, good, bad or ugly, on this thread.

[AirMiles]

Originally Posted by AirMiles

Alex, I saw your original thread on the WFCO converter. Then I started noticing the same issue with my new WFCO. I’ve been trying to figure out how the WFCO performs over the past couple of weeks. Last night, I ran the batteries down to 12.11V. Then I turned on the WFCO on 120V. It started in Bulk mode at 8:15pm at 12.45V. At 9:04 voltage was at 13.04V. At 11:16 it was at 13.23V. At 12:02am it was at 13.27V. At 12:46 it was at 13.33V. At 1:33 it was at 13.37V. At 2:45 it was at 13.42V. At 4:54 it was at 13.49V. At 6:07 it was at 13.52V. I then let the battery rest until 6:40 and voltage held at 13.00V. We then used our typical morning power and the batteries never dropped below 12.7V.

My takeaway from this is that the charger stayed in bulk for ten hours. Voltage kept climbing throughout and it appears the batteries did get fully charged. But that charge profile does not match the needs of my batteries. My PD4655 bulk charged at 14.4V, then absorption charged at 13.6V, then floated at 13.2V. The PD4655’s charging profile is a better match for my batteries based on manufacturer recommendations. Therefore, I’m still not impressed with the WFCO. It doesn’t use a 14.4V bulk as stated in its specifications. So I’m glad I have a PD4655L on order to replace my brand new WFCO.

Here’s a few pictures to document this test.

My new PD4655MBA for the WFCO 8955 has arrived and has been installed. I’m officially done testing the stock charger. Installed the new PD4655, turned on the breaker, and TADA - 14.2V was pumping into the batteries. Nice to have a converter-charger that actually works as advertised.

[AirMiles]

Got the new Globetrotter out of the trees and into the sun at its storage lot. The 600W of solar on the factory prewire had some catching up to do after spending a three-day weekend camping under a nearly full canopy of trees. Look at these production numbers! Peak production at 491W and 397W over the past couple of days. Total production of 1.48kWh while in storage for a full day without any real-time Amp draw. I knew this configuration would put up some numbers when it got unobstructed skies with run-down batteries. These numbers look great to me for just catching up at the storage lot. I can't wait to see what it will do with the combination of real-time Amp draw and run-down batteries while camping under unobstructed skies.

[youngpeck]

Originally Posted by AirMiles

Thanks for sharing your experience with your refrigerator on solar. I like having enough solar to recharge the usable battery amp hours on a good day of solar production. That way, I can use some of the battery storage on a bad solar day, or two, then recover on one good day of solar production. That appears to be what you are doing and its how my 400W solar system worked with 230AH of batteries.

Now that I have 600W of solar and still only 230AH of batteries, I probably have excess solar production. Maybe the excess solar production can power the refrigerator during the day while replacing the battery amp hours used the prior night. I just don't know if 230AH of batteries can power the refrigerator plus my other overnight overnight needs. Even if it can, how often will I run out of battery storage when the next day is overcast? If powering the refrigerator on DC causes me to run the generator frequently, it would be more efficient to just continue to use propane to power the refrigerator.

We will be finding out the answers to these questions shortly. I plan to leave Friday for up to five weeks of dry camping in the Blue Ridge Mountains. This will provide plenty of opportunity to test my solar setup and determine its capabilities. I will be posting the results, good, bad or ugly, on this thread.

It will be interesting to see how your Blue Ridge trip plays out. We were there earlier this summer and realized that finding sunny days and spots took some creativity. There were a few times that we had to run our generator perhaps every third day. Now that we are back out west, with the lower sun angles this time of year, we are continuing to have good recharging rates. If we get four or five days of no sun we might have to run the generator, but that's not an inconvenience to me, and it doesn't happen often.

[uncle_bob]

Hi

If you are trip planing there are some interesting sites to use:

https://www.nrel.gov/gis/solar.html

https://www.wholesalesolar.com/solar...n-hours-us-map

https://neo.sci.gsfc.nasa.gov/view.p...=CERES_INSOL_M

https://tyconsystems.com/html/nrel_lookup.htm

Indeed the last one on the list is a bit ugly. It does indeed give you a quick table by month for your location. Indeed there are a lot of sites with similar data out there.

If you *really* want to go crazy, you can keep track of the real time / NASA data vs your readout and see just how close you are getting at this or that location.

Bob

[pcskier]

I am in Tetons and socked in. Surprised to see I’m still getting a small charge and net positive amps in batteries with fridge (.4 amps) and propane detector (<.1 amps) as only loads. Batteries are not really 100 percent since monitor is reading what’s coming off the controller, but this solar stuff is just cool.

[AirMiles]

Here’s my September 2019 solar performance from my new 27’ Globetrotter with 600W on factory prewire. Much of this performance is messy. I was trying to use the refrigerator on DC at night and/or during the day. Most of that testing was a failure. The refrigerator in the Globetrotter is not as effective as in my flying cloud. It runs nearly continuously just to maintain adequate temperatures. Therefore running it at night is not possible. Even running during the day is difficult in September with low sun angles and long tree shading. The only practical time for me to use the refrigerator on DC is while traveling with sunshine.

[blacklab]

Air Miles,

We're looking at a GT 27, so I've been following your experimenting with DC and the new 3-way refrigerator with great interest.

In summer sun, let's assume little to no shade, and in a campground, not traveling, do you think your system will be able to run the refrigerator on DC during the day, with some additional DC draw, plus replenish your prior night's use?

Are you finding that on propane, this new 3-way seems less efficient than the refrigerator in your FC? In other words, on propane are you finding that it runs more (or even all the time) compared to your FC refrigerator on propane?

Thanks.

Cheers,
Bryan

[nryn]

Originally Posted by blacklab

Are you finding that on propane, this new 3-way seems less efficient than the refrigerator in your FC? In other words, on propane are you finding that it runs more (or even all the time) compared to your FC refrigerator on propane?

I know your question was directed to AirMiles; I just want to understand what you are asking. When running on propane, how do you know when it “runs more”? My GT fridge ran on propane for most of the summer and was nearly silent.

I had other propane draws (furnace, stove, hot water, bbq, generator, fire pit) and filled only two tanks in about 105 days of use this summer. So in my experience the GT fridge seems pretty efficient, though I have nothing to compare it to.

[uncle_bob]

Hi

You can run the fridge in these RV's a *long* time on propane. Unless you are someplace unusual (over 10,000 feet) in the summer where you need the furnace, the bottles should last for months with typical use ( = stove, fridge, occasional water heater).

Bob

[Omnial]

Originally Posted by nryn

I know your question was directed to AirMiles; I just want to understand what you are asking. When running on propane, how do you know when it “runs more”? My GT fridge ran on propane for most of the summer and was nearly silent.

I had other propane draws (furnace, stove, hot water, bbq, generator, fire pit) and filled only two tanks in about 105 days of use this summer. So in my experience the GT fridge seems pretty efficient, though I have nothing to compare it to.

I had the same experience; very satisfied running on propane and not effectively able to run on DC (360 W of solar & 240ah of AGM)

[uncle_bob]

Hi

If indeed you have a need to run a fridge on DC then you probably should get a different kind of fridge. They do make compressor based fridges that run on 12V. The obvious gotcha is that they don't ever run on propane. If the battery does not keep up, the beer gets warm.

Depending on what you get (how big it is and how well insulated) the current can be pretty low. 3 to 5A on 12V with the compressor running is not an uncommon number for a modest sized fridge. Will it run at 20% or 80% duty cycle at 80F? That depends a lot on how well ventilated the coils are ....

Bob

[AirMiles]

Originally Posted by blacklab

Air Miles,

We're looking at a GT 27, so I've been following your experimenting with DC and the new 3-way refrigerator with great interest.

In summer sun, let's assume little to no shade, and in a campground, not traveling, do you think your system will be able to run the refrigerator on DC during the day, with some additional DC draw, plus replenish your prior night's use?

Are you finding that on propane, this new 3-way seems less efficient than the refrigerator in your FC? In other words, on propane are you finding that it runs more (or even all the time) compared to your FC refrigerator on propane?

Thanks.

Cheers,
Bryan

Sorry for the delay in responding. My cellphone coverage was very poor at Mt Pisgah campground on the Blue Ridge Parkway. Solar did well there but could only get 1kWh per day. Only enough to run the refrigerator on DC for a couple of hours per day while charging my batteries from other use.

I would take my old two-way fridge from my 2017 FC25FB over the three-way fridge in the Globetrotter in a heartbeat. By more efficient I mean it cooled better. I never struggled keeping it cold. I could make enough ice for me to keep my water in my Yetti cup cold without thinking about it. With the new fridge, it runs constantly. Is very temperamental about being level. Can barely freeze two mini-ice cube Trays in 24 hours. It just is marginally acceptable for our needs. We have learned how to make it marginally effective by keeping it perfectly level. We need to level the refrigerator, not the Airstream.

I’ve had a three-way refrigerator in my Casita and it worked exactly the same. Very finicky. Needed to be perfectly level and needed to be constantly watched to make sure it was cooling enough.

Can it be run on 600W of solar while charging batteries from other use? Absolutely not. It draws somewhere between 10A and 14A while running and it runs nearly constantly even with outside temperatures in the 60s. It would take 2.4kWh per day just for the refrigerator. That would be four times solar panel wattage from 600W of solar. That level of production is possible under perfect solar conditions which rarely happen. Then I would need another 1kWh for my other usage such as lights, pumps, radio, tV. Five times the 600W of solar that fits on a 27’ Airstream is impossible to produce constantly to keep a battery bank fully charged.

The only use I’ve found for the DC fridge is while traveling in full sun with 600W of solar. It works well on DC in those conditions. Today was completely overcast with fog while I was traveling. I kept the fridge on propane as I only produced 100Wh from solar.

Based on my experience, the ability to travel safer with DC operation On perfectly sunny days with 600W of solar does not outweigh the poor performance from the Three-way fridge. I wish I had a two-way fridge again.

Also, I use way more propane than suggested above. I use about two pounds per day. The refrigerator is rated to use one pound per day. I’ve already used over 20# of propane in about fifteen days of use and the refrigerator was on electric for some of those days. I’m probably close to needing another bottle refilled. The two bottles I’ve used are 20# tanks which I had completely refilled with 20# of propane. The longest I can dry camp on a single 20# bottle of propane is about 15 days. I rarely use the propane generator but do use propane gas to cook, heat water, Furnace and refrigerator.