want to add Solar for 12 volt fridge

[mhbell]

I have a Forest River Cherokee Arctic Wolf 271RK Fifth wheel trailer with a Furrion 10 CU 12 volt fridge. We like to camp off grid sometimes for 3 or 4 days. I am thinking that a 400 watt solar system would keep the fridge cold on Sunny days. I have a 2000 watt Inverter generator for cloudy or rainy days. The fridge draws 11 amps according to the specs which is 132 watts would a 400 watt array with a MPPT controller be enough. What type system do you have? I'm thinking maybe 2 ea Lifpo4 100 amp hour batteries. this would be for the fridge and kitchen area. My trailer has the 50 watt juicer to trickle charge the Lead acid batteries. We do not dry camp that often so am trying to hold down the cost. Any suggestions would be appreciated. We do travel long distance sometimes.
Mel

 

[gibsito]

From 6pm to 8am (the period when there's no, or very low, solar charging) you'd be using 154 amp hours with the fridge alone - not even counting any other loads in your rig. At full battery charge and assuming no other charging happening, you have 180ah in your battery bank to use (since you can use 90% of each Lifepo4 battery's 100ah = 90ah for each). 180-154=26ah is all you have left for lights, water pump and all other electrical usage. That's cutting it extremely close. If it was me I'd probably (just a guess) go with at least 3 Lifepo4 100ah batteries and 600 watts of solar, unless that fridge can run on propane. If it can, I'd just do that.

 

[mhbell]

From 6pm to 8am (the period when there's no, or very low, solar charging) you'd be using 154 amp hours with the fridge alone - not even counting any other loads in your rig. At full battery charge and assuming no other charging happening, you have 180ah in your battery bank to use (since you can use 90% of each Lifepo4 battery's 100ah = 90ah for each). 180-154=26ah is all you have left for lights, water pump and all other electrical usage. That's cutting it extremely close. If it was me I'd probably (just a guess) go with at least 3 Lifepo4 100ah batteries and 600 watts of solar, unless that fridge can run on propane. If it can, I'd just do that.

Thank You for the reply. I've been told that the fridge only uses 11 amps when in defrost mode and that it uses considerably less in run mode. and at night when the fridge is not opened and it is cooler it should use even less. I can always add more panels if needed. I have the room. The fridge is a 12 volt only. so propane is not an option. will just have to wait and see how it all works out. Will keep the forum posted. My solar kit arrived today.
Mel

 

[gibsito]

Thank You for the reply. I've been told that the fridge only uses 11 amps when in defrost mode and that it uses considerably less in run mode. and at night when the fridge is not opened and it is cooler it should use even less. I can always add more panels if needed. I have the room. The fridge is a 12 volt only. so propane is not an option. will just have to wait and see how it all works out. Will keep the forum posted. My solar kit arrived today.
Mel

In that case you could be fine with what you've planned for. Best of luck, I hope it works out for you.

 

[mhbell]

solar Update
I installed the 400 watt solar kit with a MPPT Controller, and a series parallel panel array on the roof. I loaed the fridge with water bottles and the freezer with a couple of small buckets of water. Turned on the fridge on shore power for 24 hours to get everything cooled down. I then unplugged the 5th wheel from shore power and ran everything off of solar and the lead acid batteries. I ran it like this for 7 days. batteries never went below 50-60 percent.the fridge temp stayed at 38-40 deg F, and the freezer stayed at 0 to -2 deg F. I opened the fridge and freezer several times during the day and night. ran several LED Interior lights. All worked fine. The days were hot and mostly sunny with a few clouds. Not a very scientific test, but will do for now. it lets me know my system will work. I plan to add a couple of 12 volt 100 amp lifepo4 batteries when I can afford them.
Mel

 

[TheLooks]

Go with bigger batteries, once they are charged up the extra juice will come in handy at some point.

 

[Rich W.]

The problem you run into cutting it close is on cloudy days, with normal daily usage, you are not fully charged at sundown, so you might not make it through the night, especially if you run into several cloudy days in a row. But I like your trial-and-error science and the fact that you have room for more panels, and plans for more power storage. I think you’re on the right track and look forward to hearing how it goes. Also would like to know what panels you used. All my experience is with residential solar (currently 5 315w LG panels on my coach) and still using six OE config LA batteries, so its interesting to see how the 12v systems work out.

 

[mhbell]

The problem you run into cutting it close is on cloudy days, with normal daily usage, you are not fully charged at sundown, so you might not make it through the night, especially if you run into several cloudy days in a row. But I like your trial-and-error science and the fact that you have room for more panels, and plans for more power storage. I think you’re on the right track and look forward to hearing how it goes. Also would like to know what panels you used. All my experience is with residential solar (currently 5 315w LG panels on my coach) and still using six OE config LA batteries, so its interesting to see how the 12v systems work out.

I installed 4ea 100 watt HQST panels From a HQST 400 watt Kit with MPPT Controler and 10 AWG cables Everything included for less than $600. The setup is working great. Will add Lifepo4 batteries when I can afford it. I think the panels are the same as renogy.
Mel

 

[gibsito]

Those are the same panels I installed on my sister's Lance 1575 a couple of years ago. It is just a 200-watt system with 100ah AGM battery. Still charging without skipping a beat.

 

[Colorado High Country]

A bit late to this question, sorry - 400 watts of solar , on a sunny day ( for 6-7 hours?) , will provide close to 20 amps charging per hour to your batteries. If your fridge is actually drawing 11 amps ( that's suspicious) it would consume 264 amps a day, compared to 120 amps from the solar panels... anyone else think 11amps is not likely accurate?

 

[TheLooks]

Not sure without seeing the specs but in general, low volts equals high amps and vice versa. There is no free lunch or everything would be 12 volts. Only way to tell is turn it on and put an amp meter on it.

 

[mhbell]

A bit late to this question, sorry - 400 watts of solar , on a sunny day ( for 6-7 hours?) , will provide close to 20 amps charging per hour to your batteries. If your fridge is actually drawing 11 amps ( that's suspicious) it would consume 264 amps a day, compared to 120 amps from the solar panels... anyone else think 11amps is not likely accurate?

The 11 amp draw is only during defrost cycle I've been told. I did a test and ran off of just the solar and LA batteries. Went for 5 days without the batteries going below 52 percent. Could do even better with Lifepo4 batteries.
Mel

 

[Mills]

Our East to West Alta has the upgraded 170 watt package(50 watt and 120 watt panels). So far we haven't had a problem but we've had sunny days. The battery does drop below full in the early morning. I want to add another panel for quicker charges and cloudy days.