Traveling Light Reflections
Stock Solar with 12V RV Refrigerator Not Charging Battery
Why Doesn't Your Solar Panel Not Always Recharge Your Stock RV Battery when You are Off Grid?
Why does the stock battery that came with my RV fail to keep its charge even though you have solar panels? There are a number of reasons that this happens. 1. Small lead acid battery supply by dealer, 2. The new style 12V compressors use a LOT more energy than the older evaporation refrigerators and lastly, 3. The stock solar panel is barely enough to keep your battery charged on the sunniest days. Any cloudy days or shade and it will never have a chance of keeping up.
I am putting the data table in the beginning here, and I will explain how and where I got each value in the article.
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Stock Dealer Supplied RV Battery
First we will start with the basic battery that most dealers supply you when you buy an RV. This is a standard Group 24, 27 or 31 lead-acid battery. These batteries typically have around 100 amp-hours of energy or even less if it is a group 24. Here is the catch, a lead acid battery can only be discharged down to 50% of its capacity. This means that the 100 Amp-hour battery, really only has 50 Amp-hours to give. As a side note, the dealer supplies the battery, not the RV manufacturer.
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RV 12V Compressor Refrigerator
The largest energy consumer in a stock RV is a 12V compressor refrigerator. An example is the Furrion 10-cubic foot model that comes with my 2023 Grand Design 226RK. According to Furrion’s specifications, using a 100 Amp-hour lead acid battery, the refrigerator will run at 4.08 amps for 49 hours when the temperature is 77 degrees. However, at 90 degrees it will consume 6.45 amps and only run for 31 hours before depleting the battery.
I confirmed this by testing the current of our refrigerator on a 76 degree day. It used about 4 amps while running. This told me Furrion’s specs were based on a 50 Amp-hour battery running an average of ¼ of the time. On for ¼ of the time and off for ¾ of the time.
Based on this data, the refrigerator will use about 25 amp-hours per day. The refrigerator alone will use ½ the battery in one day. In 2 days, the refrigerator will completely deplete the battery. If you are running the refrigerator in higher temperatures the battery will be depleted even sooner.
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Stock Solar Panel
We just discussed the battery and the refrigerator. Next we will discuss the solar panel. Our RV came with a Furrion 165 Watt solar panel. Under the most ideal conditions this could put 13 Ah per hour back into the battery. However I have never seen ideal conditions nor if they existed, they would not exist for long on a given day.. However, if they did you would be able to put 65 amp-hours into the battery. This will NEVER happen. For one thing, I have only seen around 75% of the 165 watts come from my 165 watt solar. This was only for short periods on the best of days. On an average day you will get maybe 40 Amp-hours from the panel, if it is a mostly cloudless day. On a cloudy or rainy day you may see 10Ah or less per day.
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Other Loads on the Battery
Other loads on the battery may also be draining it. This includes your lights at about .25 amps each, your vent fans at about 3 amps on max, opening and closing your awning, other parasitic loads like all of those little lights and sensors that are still on when everything else is off. So, 6 lights on for 5 hours uses 7.5 Ah. A fan on high for 6 hours will use 18Ah, for 12 hours it will use 36 Ah. Other parasitic loads I am estimating at 3Ah/day.
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Summary
So in summary, Here is a look at the starting battery energy, the added energy from the solar panel and average daily loads. Even with that additional energy gained from the solar, the battery will only last for 4-days. Please note, these calculations are based on realistic but assumed, rough and variable estimates.
This is why at the end of an off the grid adventure you may need to run a generator to close your slide and raise your electric jacks. Hopefully soon, all dealers and/or manufacturers will start supplying all new RV with at least 200 Ah lithium batteries.
Links and references:
What is an Amp Hour - Beginners Guide
https://www.travelinglightreflections.com/what-is-an-amp-hour-beginners-guide
Furrion 10 Cu Ft Refrigerator
Specs https://cdn.accentuate.io/6037138899127/5237057388633/MS-FCR10DCGTA-V1.2-v1606962744880.pdf
User Manual
https://cdn.accentuate.io/6037138899127/5237057552473/IM-FHA00097_V3.0_EN-(1)-v1606962786356.PDF
Furrion 165W Solar Panel
About Lead Acid Batteries
https://louwrentius.com/a-practical-understanding-of-lead-acid-batteries.html
