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Old 11-08-2018, 02:31 PM   #1
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My 2019 Factory Solar experience

2019 Flying Cloud 26 with factory 80 watt solar and two AGM batteries. 50 amp, 2 AC units.
California state park, 30 amp service, 70 degree days, 40 degree nights. Parked South/North orientation, panels on rear, northern side of trailer. No shade.

At 9PM, I went through the trailer and turned off all electrical loads possible, and switched water heater and refrigerator to propane. I disconnected shore power.

Battery shows 100% charged.
Battery voltage 13.6V at meter.
Solar amp hours 364.

Set furnace at 65 degrees. Turned on the inverter, and turned on my 4 amp Resmed CPAP machine.

Up at 3AM for a bathroom call.
Battery voltage 12.5V

6AM (dark outside) Turned off inverter. Furnace came on twice in the morning. Turned furnace up to 68 degrees
Battery life 50%
Battery voltage 12.3V
Solar voltage 1.2

7AM
Battery life 45%
Battery voltage 12.2V
Solar voltage 12.3 ?
Solar charge 0.3, red light is on.

8:30AM
Battery life 65%
Battery voltage 12.5V
Solar voltage 12.5V
Solar charge 0.3

Had to leave, came back at 12PM.
Battery life 100%
Battery voltage 13.1V
Solar voltage 13.1
Solar charge 5.0 amp
Solar amp hours 376

Turned inverter back on, been sitting here for an hour on the computer.
Battery life 90%
Battery voltage 12.7V
Solar voltage 12.7V
Solar charge 4.5 amp
Solar amp hours 381

Once I turn off the computer and inverter I expect to fully charge to 100%.

So, with good discipline, I should be able to survive more than one overnight, with good weather get a 100% charge each day. If temps drop to the 30's I either have to lower the thermostat or get a catalytic heater or...
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Old 11-08-2018, 02:39 PM   #2
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80 watts of solar is basically nothing. The smallest system that I install is 200 watts (2 panels) but typically go with 400 watts for far better energy transfer. With your 80 watts of solar and your 2 smaller AGM batteries, you might be able to make it thru a night, but what happens if you run into a couple of days of clouds with no sun?

Just a thought............
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Old 11-08-2018, 02:51 PM   #3
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Hi

The magic stock solar display panel is trying to look at voltage and guess at battery charge state. Unless you get to 13.6V and stay there for a couple hours of charging, you likely are closer to 80% than you are to 100%. It's not that the panel is defective or that it's lying to you. It simply is doing the best it can based on a voltage reading. It has no way do tell just where in the final part of the charge cycle the battery is.

Further complicating things, the panel and charger are indoors. They have no way to tell what the battery temperature actually is. Around freezing a battery that is at the "stop using / 50% charge" point can be up around 12.6V. You do not want to go past this point. The wear and tear on the batteries goes up quickly if you do.

Bob
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Old 11-08-2018, 05:55 PM   #4
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Thanks for sharing your solar/battery usage experience. The data seems about right based on my solar usage experience.

You got about 17 Amp Hours (Ah) of battery charge from an 80 Watt panel through 2 PM. My experience is that three times solar panel wattage is a good day and four times is a great day. Three times 80W is 240W, then divide by 13.0 average battery voltage equals 18.5 Ah on a good day. Four times 80W is 320W, divided by 13.0 average battery voltage equals 24.6 Ah on a great day. You may be able to maintain fully recharged batteries while boondocking if you can keep your usage to around 20 Ah per day. Like Lewster said, 20 Ah per day is not much. My typical daily usage is around 60 Ah and my highest days can be around 100 Ah.

Here is a table that shows "resting" battery state of charge voltages at various temperatures that Uncle_Bob was discussing: http://all-about-lead-acid-batteries...re-correction/ The problem with tables like this is that a boondocking battery is never "resting".
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Old 11-09-2018, 06:41 AM   #5
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Hi

The other problem with coming up with a table of voltage vs temperature is that they are very dependent on exactly what went into the plates and electrolyte in the battery. Even with a single brand of battery, there apparently are variations by region of the country....

Bob
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Old 11-09-2018, 09:10 AM   #6
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We just spent a night in Ely NV. Woke up to 14F. The furnace ran all night set at 58 degrees and my husbands CPAP. Don’t have solar. Battery read 11.8 in the am. Don’t need solar for one night. We also had lights and tv on before going to bed. 30’ Flying Cloud.
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Old 11-09-2018, 09:36 AM   #7
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Quote:
Originally Posted by tschambo View Post
We just spent a night in Ely NV. Woke up to 14F. The furnace ran all night set at 58 degrees and my husbands CPAP. Don’t have solar. Battery read 11.8 in the am. Don’t need solar for one night. We also had lights and tv on before going to bed. 30’ Flying Cloud.
Check the battery voltage/temperature table for 11.8V at 14F. http://all-about-lead-acid-batteries...re-correction/ Your battery was at a "zero" state of charge. Basically at a level where permanent damage will occur. Of course, having solar would not have helped in this situation since much of the drawdown was after sunset.

What you will need if you continue to encounter these conditions is a battery bank with more Amp Hours or a generator to run in the evening to boost charge the battery while powering the TV.

My first set of Airstream batteries only lived for ten months from using the furnace in cold temperatures and drawing down the battery too deeply. I'm all for using a battery like a propane exchange tank - replace it when it runs out of juice. But if you continue drawing down the battery to a temperature-compensated "zero" state of charge, you will be replacing your battery very frequently. It may be more cost effective to increase the size of your battery bank rather than frequently buying new batteries.

This comment is intended to help others learn from my past mistakes.
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Old 11-09-2018, 12:18 PM   #8
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Quote:
Originally Posted by tschambo View Post
We just spent a night in Ely NV. Woke up to 14F. The furnace ran all night set at 58 degrees and my husbands CPAP. Donít have solar. Battery read 11.8 in the am. Donít need solar for one night. We also had lights and tv on before going to bed. 30í Flying Cloud.
You may very well need new batteries.
Consider running your generator until you go to bed. Get a book to read. You should be fine. 👍

Bob
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Old 11-09-2018, 04:32 PM   #9
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CPAP can run on 12volts

Depending upon which Resmed CPAP you have, a 12 volt adaptor can be purchased, that way you would not have to run your inverter. Dang it, Airstream stopped putting in 12 volt sockets.

Something like this - https://www.resmed.com/epn/en/consum...w-output-.html
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Old 11-09-2018, 06:45 PM   #10
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Originally Posted by Acheron2010 View Post
So, with good discipline, I should be able to survive more than one overnight, with good weather get a 100% charge each day. If temps drop to the 30's I either have to lower the thermostat or get a catalytic heater or...
Maybe. I agree what others are saying about dynamic voltage readings. You never really know the Battery SOC until they have rested for "some" time but by that time, you have further confused the equation with more DC change, whether charge or discharge.
If you are want to get a better picture of how many amp hours you are using/replacing with solar alone (80 isn't much) you need a meter with a shunt that can total amp hours. There are several and they are all in the $200 range. Trimetric, Victron, Expion 360 will all give you the info you need.
Getting the CPAP over to the straight DC side will help too. Inverters are great but they all use up DC power to make, well dc power in this case. Your CPAP runs on DC anyway so I'd cut that middleman while you sleep. There are small Lithium battery packs that will last 3 nights before needing charged. Every AH counts.
Airstream's solar option, while better than nothing is really just teasing the consumer and not a boondocking package by any means. Good to build on but hey, you might be frugal enough to make it work for you and applaud you for trying. Good luck and thanks for the info.
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Old 11-09-2018, 07:28 PM   #11
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I have an A&M Solar installed 500 watt panel system with two Lifeline 235 aH AGM 6 Volt Batteries on our 2017 25FB.

I was told by A&M to try not to let the batteries go below 70 percent and never to 50 percent or lower. The battery life will be appreciably reduced with that much draw down, and quality AGM batteries are very expensive.

You may be a candidate for a lithium battery system which lets you draw down pretty low without doing damage. They are very expensive and are temperature sensitive and may not charge properly in very cold weather.

Side note. The Airstream factory "solar ready" wiring system is adequate for the small wattage systems that they seem to install. A larger, more capable system will require heavier wiring and the appropriate heavier duty control systems.

I also carry a Honda 2000 generator for very cold weather heating.
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Old 11-10-2018, 08:54 AM   #12
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Guess this really shows my ignorance. I thought half the battery charge meant have the numbers o the display. Duh. We actually have a Honda 2000 generator we ran the first night with freezing temps in Jackpot but then thought with as little as the number dropped we could get away without it the 2nd night. Ha. Guess not. Thanks for educating me.
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Old 11-10-2018, 09:55 AM   #13
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Hi

One further hint if you are charging batteries from a generator - it takes a lot longer than you might think. Four hours of run time per day is a pretty good guess at the minimum time to keep things up to "full". Two hours in the morning and two hours in the evening is about as close as you want to cut it.

Bob
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Old 11-10-2018, 10:35 AM   #14
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Iím wonderingóis it possible to charge the batteries from solar and the generator at the same time or is it one or the other?
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