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Old 07-27-2015, 03:58 PM   #1
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How much solar do I need to be able to watch DVD movies in the evening?

I don't want to run my generator when the sun goes down so I'm seriously considering going solar. My goal is to be able to power the big TV and dvd and still have enough batt power for the fridge, status monitor, etc to last through the night. How much solar will I need and what do you think it'll cost?
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Old 07-27-2015, 04:03 PM   #2
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What will power your solar when the sun goes down? What you are looking at is battery capacity in amp hours. Not how much solar.
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Old 07-27-2015, 05:05 PM   #3
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What will power your solar when the sun goes down? What you are looking at is battery capacity in amp hours. Not how much solar.
Not really. If the OP is looking at how much solar capacity is needed to recharge the house batteries after an evening of DVD watching, then a good rule of thumb would be that you want the solar panel(s) to provide enough amps to recharge the house batteries in about 6 hours.

That will account for the fact that you don't get full charging capacity for all the hours of daylight, only when the sun is at a decent angle to the panel, so 12 hours of daylight will give you maybe the equivalent of 6 hours full capacity.

For example, my Interstate's dinky 50watt solar panel produces a nominal 4.16 amps at 12v, so 6 hours of charging would be 25 amps. If my television with built-in DVD player used more than 25 amps in an evening of DVD-watching, I'd want to upgrade my panel.

By the way, note how neatly the numbers work out. Given the relationship between volts, amps, and watts, since we're looking at 12 volts for 6 hours, simply multiply the number of amps needed by 2 to find the size of the solar panels needed. If your normal evening usage is 45 amps— for example— then you'd need a minimum of (45×2=) 90 watts of solar panel to recharge the system in one day.
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Old 07-27-2015, 05:23 PM   #4
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Thanks for the tip. Also remember that one should not run a battery way down and expect it to come back when recharging. I believe the conventional wisdom is that depleting the battery more than 50% damage can cause damage. Take a look at the battery capacity of your coach and compare that to your needs. In the example above, a 45A overnight draw means that the battery(ies) need to have a capacity of at least 90A.
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Old 07-27-2015, 05:33 PM   #5
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Thanks for the tip. Also remember that one should not run a battery way down and expect it to come back when recharging. I believe the conventional wisdom is that depleting the battery more than 50% damage can cause damage. Take a look at the battery capacity of your coach and compare that to your needs. In the example above, a 45A overnight draw means that the battery(ies) need to have a capacity of at least 90A.
That makes the rule of thumb even easier, come to think of it. Take the total amp-hours of your house batteries, and get at least the same number of watts of solar panel. So if you have 160 amp-hours (typical for two Group 24s in parallel) then you'd want at least 160 watts of solar panel to recharge them from a 50% charge state in one day of daylight.

But if you get even more solar capacity than the amp-hours of your batteries, then you've got reserve charging capacity for days when you have less than a full day of daylight.
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Old 07-27-2015, 06:32 PM   #6
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Not sure of all the technical stuff, but I've got 300 watts of solar and two 27 series batteries. I can easily watch a DVD movie on a fairly large screen (sorry, but don't have the dimensions handy) and not drain the batts below 50% by the morning. As I recall, it's more like 75% down, but that's a guess from memory. Of course, you have to have some sun the next day to bring them back up.
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Old 07-27-2015, 06:35 PM   #7
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Please put the time in the numbers being tossed around. It is not 45 amps it is 45 amp hours. One amp for 1 hour = 1 amp hour.

My microwave, powered by my inverter, requires 90 amps to run. Since I am only using it for lets say 6 minutes, that is 1/6 of an hour. So the energy removed from the batteries is 90/6 = 15 amp hours. Batteries store energy in amp hours, not in amps.
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Old 07-27-2015, 06:38 PM   #8
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You might like to read my post that I made yesterday:

http://www.airforums.com/forums/f450...er-138719.html
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Old 07-27-2015, 06:45 PM   #9
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Please put the time in the numbers being tossed around. It is not 45 amps it is 45 amp hours. One amp for 1 hour = 1 amp hour.

My microwave, powered by my inverter, requires 90 amps to run. Since I am only using it for lets say 6 minutes, that is 1/6 of an hour. So the energy removed from the batteries is 90/6 = 15 amp hours. Batteries store energy in amp hours, not in amps.
True, house batteries are rated in amp-hours while starting batteries are rated in amps, and we're discussing house batteries. Thank you for the correction.

But the point remains, that my rule of thumb is— the minimum amount of solar panel, in watts, is equal to the number of amp-hours of battery capacity, if you want to be able to recharge the batteries in one day on solar alone. More solar charging capacity of course is better because you won't always have a full day of sunlight each day.
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Old 07-27-2015, 06:47 PM   #10
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Like horsepower, you can never have too much . I installed my own 400 W solar system for about $1500. My system includes a battery monitor, which in my opinion is extremely useful in understanding your energy needs and making sure your batteries are not discharged more than the manufacturer's recommendations. I'm still using the stock group 31 batteries (2) that came with my AS, so my useful battery capacity is only around 100 A*hours. I might upgrade the battery system in the future after having more experience with dry camping.

My guess is a comparable system installed by a professional will run in the neighborhood of $3K.
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Old 07-27-2015, 07:00 PM   #11
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Originally Posted by Protagonist View Post
True, house batteries are rated in amp-hours while starting batteries are rated in amps, and we're discussing house batteries. Thank you for the correction.

But the point remains, that my rule of thumb is— the minimum amount of solar panel, in watts, is equal to the number of amp-hours of battery capacity, if you want to be able to recharge the batteries in one day on solar alone. More solar charging capacity of course is better because you won't always have a full day of sunlight each day.
I agree fully
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Old 07-28-2015, 01:30 PM   #12
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Old 07-28-2015, 01:35 PM   #13
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how much solar is too much? 300W on an AI?

Enjoy the solar discussion - we are serious boondockers in our 2012 AI Lounge.

I added three 100W panels from AMSolar, enjoying 15+ charge amps during the sunshine.

I still have the stock Tripp-Lite charger/inverter and stock solar controller.

A couple times I noticed midday that the solar controller display was blinking with 16+Vdc showing - an overcharging situation for sure.

I turned on a few loads (inverter, lights, fans) to suck some juice, and it seemed to reset things down to a more normal voltage on the solar controller display.

Do you think my Tripp-Lite is overdoing it, or is the solar controller not controlling things properly?

What recommendations do you have for replacing the solar controller or Tripp-Lite? I also replaced the stock house batteries with two Lifetime AGM 6V biggies wired in series, and the Lifetime documentation says these can handle a much higher charge current than 55A (Tripp-lite max).

Anyone add a larger separate charger to charge up the house batteries faster when driving?
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Old 07-28-2015, 02:00 PM   #14
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Your system would benefit greatly from a better quality solar charge controller like the Blue Sky 2512iX-HV and their iPN PRO remote panel. You will get significantly more amps to your batteries by utilizing their 'solar boost' technology.

Also, you will see much better battery charging with a Magnum MMS-1012 inverter/charger and the ME-RC remote.

And BTW, they are LIFELINE batteries, not Life'time'. :-))


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