The number of solar panels you’ll need for your RV highly depends on the efficiency of the solar panel you get, the size of your battery bank (I’m referring to your total battery bank capacity) & your RV electrical consumption. The current general rule of thumb is one (1) 100W solar panel can generate an average 30 AH/d, so all you need to do is multiply the number of panels by how much power you need.
I do recommend researching on what solar panels are available to you that fit within your budget since there are now 415-watt solar panels with 22.3% efficiency, and as of March 2020, also 500 watt solar panels now available. Having a more powerful & efficient solar panel can help save space since the space on the RV roof is a bit limited space.
What Size Solar Panel Do I Need To Charge My RV Battery?
Standard solar panels 65×39 inches can be used to charge a 12v 100w battery.
Depending on the model of your dedicated solar battery charger, it can give around 13.6v-17v. A 12v solar panel with a 10 watt specification can be used to charge a 12V battery since it can have a peak voltage of 13.8v which is enough to charge a 12V battery. If you have more batteries, then it will take longer. This is also dependent on the amount of sun and the efficiency of your solar panels.
How Do You Hook Up Solar Panels To Charge An RV Battery?
You need to connect a charge controller to your RV battery and the other end to the solar panel so it can safely regulate the flow of electricity. Directly connecting the solar panel to your RV battery can trigger your 12v battery to start gassing up since the 13.5v (minimum) electricity from the solar panel will be too fast for the battery to handle. I explain more about RV batteries and overcharging in an article, in case you want to learn more how RV batteries work.
How Long To Charge 12V Battery With Solar Panel?
How long it takes to charge a 12V Battery with a solar panel will be again, be dependent on the amount of sunlight you get, and the solar efficiency, size and amp output of your solar panel, and how big your battery is, but generally, a one (1) amp solar panel can typically charge your 12v battery from 50% to 100% in around 5-8 hours.
We can use this formula to compute for a lead acid battery charging time (which assumes to be able to get the battery to 90% charging capacity) as well:
Lead Acid Battery Capacity (in Watt hours) x 2 / Rated Panel Power (in Watts)
As an example, if you want to charge a 12V 10 Amp hour lead acid battery (120Wh) from 50% to full charge with one (1) 10 Watt 18 Volt solar panel:
Time = (60Wh x 2) ÷ 10 Watts = 12 hours
Note that this formula for charging time applies when the weather is around 25°C and the sunlight is directly hitting the solar panel at a 90° angle which will result in a 100% output from your solar panel. When the temperature starts to rise, the solar panel’s output will start to decrease by 0.5% for every degree above 25°C.
When it comes to the direction of the sunlight hitting the solar panel, the power output will start to drop as well (this does not factor in other weather conditions like haze, fog, clouds) which will significantly slow down the charging time.
What’s The Best Battery For RV Solar?
Honestly speaking, it really will depend on you, your budget and your plan. If you have money for lithium iron batteries (LiFePO4) are the best choice for the number of cycles and battery depth of power. If you want to read more about the different batteries available for your RV you can read up on them at this article. When it comes to brands that are high quality are from Battle born, Renogy, and expert power are the premium brands on the market.
These batteries will give you anywhere from 2500 to 7000 cycles, which is the amount of time that the battery can be emptied and recharged again. As compared to lead acid that only have cycles of 200 to 400 times and have a lifespan of 2 to 4 yrs. As where these Lithium iron batteries are rated for 10 years or more.
What Can I Use Instead Of Solar Panels?
With technology constantly changing, there are other alternative power sources and/or appliances that you can use other than solar panels, with gas generators at the lowest cost investment to battery storage and wind generators. There are quite a few options to choose from, such as:
- eRV’s RV Wind Generators or Wind & Sun Wind Generators & Turbines
- Portable suitcase-style solar panel kits like Renogy 200 Watt 12V Monocrystalline Foldable Solar Suitcase
- Solar Appliances
- Portable Generators that generate between 2000 to 4000 Watts. I explain more about this in detail in the article I’ve written HERE.