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Old 09-29-2018, 10:25 AM   #1
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Solar Panel to charge battery

Just purchased a new Cedar Creek Hathaway edition 5th wheel. Was wondering if anyone has used solar panels to charge their battery. Will a 40 AMP solar panel keep the batter charge to run a 1000 w inverter in storage for about 8 or 9 hours to cool down a whirlpool residential refrigerator before hooking up to the truck to tow on the road.
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Old 09-29-2018, 10:41 AM   #2
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Just purchased a new Cedar Creek Hathaway edition 5th wheel. Was wondering if anyone has used solar panels to charge their battery. Will a 40 AMP solar panel keep the batter charge to run a 1000 w inverter in storage for about 8 or 9 hours to cool down a whirlpool residential refrigerator before hooking up to the truck to tow on the road.
Presumably you mean a 40 WATT panel. That reefer probably draws about 90 watts when running normally and substantially more when cooling down from room temperature. Need to know how many batteries you have since you are only talking about 8 or 9 hours, you might make it with two or more batteries with or without the panel. 40 watts isn't going to make or break the equation.

Now 40 AMPS would, but only if the sun is shining.
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Old 09-29-2018, 10:58 AM   #3
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I have two batteries. One powers the camper and one powers the fridge.
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Old 09-29-2018, 11:15 AM   #4
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I have two batteries. One powers the camper and one powers the fridge.
One battery will be really, really close for 8 hours. At 90 watts (which is too conservative) will draw about 7.5 amps. If you have a single battery, 50% discharge would be close to 8 hours. However, my Frigidaire draws 600 watts for about 15 minutes out of a 7 hour period, when the reefer is already cold. I suspect that a warm Frigidaire will draw that much for far more than 15 minutes. That is 50 amps at 12 volts and after one hour at that load it will totally deplete your single battery and the additional 40 watts from a solar panel won't help much.
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Old 09-29-2018, 12:20 PM   #5
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I won't try to teach you solar energy specifics but any type of Solar System that is less than 200 Watts Is pretty much useless. I currently have 500 Watts of solar hooked to three 120 amp hour batteries With a 2500 watt inverter. I can pretty much watch Satellite TV anytime I want. If I want a slice of toast with my morning breakfast I don't need To hook up the generator. When it comes to solar power , Go big or go home.
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Old 09-29-2018, 12:40 PM   #6
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I won't try to teach you solar energy specifics but any type of Solar System that is less than 200 Watts Is pretty much useless. .... When it comes to solar power , Go big or go home.
Nonsense. I am a full-time boondocker, and I live just fine on a Renogy 100 watt suitcase solar panel. Thousands of others do too. I've only used my generator for 3 hours total this year, on a couple of occasions when I had multiple days of rain.
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Old 09-29-2018, 12:41 PM   #7
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I won't try to teach you solar energy specifics but any type of Solar System that is less than 200 Watts Is pretty much useless. I currently have 500 Watts of solar hooked to three 120 amp hour batteries With a 2500 watt inverter. I can pretty much watch Satellite TV anytime I want. If I want a slice of toast with my morning breakfast I don't need To hook up the generator. When it comes to solar power , Go big or go home.
Just trying to see if there is a way to cool down the fridge in storage where there is no power
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Old 09-29-2018, 12:48 PM   #8
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100 watts will be adequate if all you are running are a few LED lights and the refrigerator is running on Propane. The gentleman stated he has a 1000 Watt inverter. Assuming he makes use of it to even a small degree, 40 watts Is a spit in the bucket and won't keep up. It appears he is referring to a residential style compressor driven refrigerator. 40 watts will never do it.
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Old 09-29-2018, 01:25 PM   #9
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100 watts will be adequate if all you are running are a few LED lights and the refrigerator is running on Propane. The gentleman stated he has a 1000 Watt inverter. Assuming he makes use of it to even a small degree, 40 watts Is a spit in the bucket and won't keep up. It appears he is referring to a residential style compressor driven refrigerator. 40 watts will never do it.
Yes it is a residential refrigerator. and thanks
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Old 09-29-2018, 03:37 PM   #10
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You're welcome. Just so you know I live full time Boondocking in the Arizona desert and have done so for the last 5 years.
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Old 09-29-2018, 04:14 PM   #11
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p=IV

Thus a 100 watt panel could produce 8 amps per hour.

Most likely 30 amps a day.

A residential refrigerator at 500 Watts requires 40 amps + 15% per hour. About 46 amps.

So likely it will run a fridge about 45 minutes per day. OK in Idaho under a tree, Not so good in Texas on the road.

A 12 volt battery can furnish about 40 amps per charge. About 50 minutes.run time.
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Old 09-29-2018, 04:30 PM   #12
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p=IV

Thus a 100 watt panel could produce 8 amps per hour.

Most likely 30 amps a day.

A residential refrigerator at 500 Watts requires 40 amps + 15% per hour. About 46 amps.

So likely it will run a fridge about 45 minutes per day. OK in Idaho under a tree, Not so good in Texas on the road.

A 12 volt battery can furnish about 40 amps per charge. About 50 minutes.run time.
Yes...and no. as I wrote, a modern, big residential reefer like a Frigidaire 22 cu/ft averages 90 watts on the DC side. Once cooled down, it would last about 8 hours without solar, alternator or converter before you hit 50% SOC on a single battery.
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Old 09-29-2018, 04:42 PM   #13
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Maybe under perfect circumstances. In my experience the most I can get out of a 100 Watt panel is about 5 amps. That would lower your numbers significantly. I use number 8 wire between the solar panels and controller with a run of no more than about 7 or 8'.
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Old 09-29-2018, 04:55 PM   #14
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First, you need this calculator to assess performance of the solar panel and the performance of the fridge.

Start with the panel. A 40 watt panel delivers only about 3.3 amps in full sun. That's 3.3 amps per hour...3.3 amp-hours per hour. Assume about 50% efficiency over the course of a day. Let's keep it easy and say 1.7 amps AVERAGE over 12 hours. On a good day, you'll put about 20 amp hours into the battery with that panel.

Now, using others' estimates, let's assume your fridge pulls an AVERAGE of 100 watts to run for 8 hours while cooling down. Plug in 100 watts and plug in 12 volts (even though the fridge is a 120 volt fridge, it's fundamental power source is the 12 volt battery being stepped up thru the inverter.

Using this estimate, the fridge will pull 8.3 amps/hour for 8 hours which equals 66.4 amp hours. That's a 46 amp-hour deficit.

For argument's sake, let's say your fridge cooling and your solar gain cycle coincide (not actually likely, but let's assume.) So, your solar panel is adding 18 to 20 amp hours at the same time the fridge is sucking 66. Is that do-able? Maybe.

Now, lets say you have a basic Group 24 flooded cell battery...the small one commonly thrown in by dealers. They have a TOTAL capacity of about 75 to 80 amp hours. You get to use half of that. So your 46 amp hour suck is way too much even when supplemented by solar, and it has to be perfectly timed with the time the solar panel is contributing power to the system. Cooling the fridge overnight would be a recipe to ruin that little battery.

If you have two 6-volt golf cart batteries in series, their total USABLE capacity is between 100 and 125 amp hours. No sweat with or without the solar panel.

Use the calculator and do accurate math with real numbers from your equipment: Fridge, Battery (or batteries), and Solar Panel. Allow a margin for error for inverter inefficiency, parasitic draws from the CO/Propane detector, etc. and be conservative with your estimates...including both the peak draw for the fridge when starting from warm and its average draw once cool.

Get more solar. A big rig like yours would benefit from a 400 watt installation. Renology is another good brand. Learn before you buy. Don't use factory-installed house wiring for solar. It's not heavy enough.

Good luck.
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Old 09-29-2018, 04:59 PM   #15
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You're welcome. Just so you know I live full time Boondocking in the Arizona desert and have done so for the last 5 years.
Just thinking if I could get something to work to cool it down in storage while I am at work before we hook up and head out on our camping trip and then hook up to shore power at the campsite we do not boondock
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Old 09-29-2018, 05:05 PM   #16
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Just thinking if I could get something to work to cool it down in storage while I am at work before we hook up and head out on our camping trip and then hook up to shore power at the campsite we do not boondock
Do you have a charge line from your TV to the TT? If so, you can cool down when you start out anyway. What I have done is to put everything into the freezer when I start out since the reefer will drop that temperature faster than the refrigerator section. In about 2 to 3 hours it gets below 40 so then I move things to the refrigerator section. The cold food in the freezer section helps cool it more quickly and the smaller volume of the freezer helps as well. Maybe put a couple of frozen gallon jug milk containers in as well.
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Old 09-29-2018, 05:06 PM   #17
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Jimmoore, Very well stated...
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Old 09-29-2018, 05:15 PM   #18
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First, you need this calculator to assess performance of the solar panel and the performance of the fridge.

Start with the panel. A 40 watt panel delivers only about 3.3 amps in full sun. That's 3.3 amps per hour...3.3 amp-hours per hour. Assume about 50% efficiency over the course of a day. Let's keep it easy and say 1.7 amps AVERAGE over 12 hours. On a good day, you'll put about 20 amp hours into the battery with that panel.

Now, using others' estimates, let's assume your fridge pulls an AVERAGE of 100 watts to run for 8 hours while cooling down. Plug in 100 watts and plug in 12 volts (even though the fridge is a 120 volt fridge, it's fundamental power source is the 12 volt battery being stepped up thru the inverter.

Using this estimate, the fridge will pull 8.3 amps/hour for 8 hours which equals 66.4 amp hours. That's a 46 amp-hour deficit.

For argument's sake, let's say your fridge cooling and your solar gain cycle coincide (not actually likely, but let's assume.) So, your solar panel is adding 18 to 20 amp hours at the same time the fridge is sucking 66. Is that do-able? Maybe.

Now, lets say you have a basic Group 24 flooded cell battery...the small one commonly thrown in by dealers. They have a TOTAL capacity of about 75 to 80 amp hours. You get to use half of that. So your 46 amp hour suck is way too much even when supplemented by solar, and it has to be perfectly timed with the time the solar panel is contributing power to the system. Cooling the fridge overnight would be a recipe to ruin that little battery.

If you have two 6-volt golf cart batteries in series, their total USABLE capacity is between 100 and 125 amp hours. No sweat with or without the solar panel.

Use the calculator and do accurate math with real numbers from your equipment: Fridge, Battery (or batteries), and Solar Panel. Allow a margin for error for inverter inefficiency, parasitic draws from the CO/Propane detector, etc. and be conservative with your estimates...including both the peak draw for the fridge when starting from warm and its average draw once cool.

Get more solar. A big rig like yours would benefit from a 400 watt installation. Renology is another good brand. Learn before you buy. Don't use factory-installed house wiring for solar. It's not heavy enough.

Good luck.
Thank you I am new with this residential refrigerator and 5th wheel. and we love it our last camper was a travel trailer
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Old 09-29-2018, 06:18 PM   #19
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Yes I do have a charge on my TV that works on the fifth wheel it worked fine on a 500 mile trip two South Dakota and I will use your suggestion in putting things in the freezer. and THANK YOU
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Old 09-29-2018, 06:35 PM   #20
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Yes I do have a charge on my TV that works on the fifth wheel it worked fine on a 500 mile trip two South Dakota and I will use your suggestion in putting things in the freezer. and THANK YOU
Personally, after owning both an adsorption unit and a residential unit, the only, only downside of a residential unit is starting out from a lot without power. If that is the only problem, it is nothing.

Enjoy
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