Choosing How to Power Your RV
 An Analysis of What You Really Need

The first thing that needs to be considered is what are your final and actual goals for your RVs power system.  Basically, do you plan to use the RV for long weekends or do you plan to use it for long-term stays of a week or more?  Another consideration is where you will be using your RV.  Will you be mostly staying in RV parks with full hook-ups or will you be using it off the grid?  Also, how much do you want to spend and can you do the work yourself? 

A complete solar, battery, and inverter system can be very expensive. One of the reasons I started with considering your “final” goals is because by slowly adding to a system without a final plan can cost a lot more than starting with a final goal and planning for that.  For example, I have bought multiple inverters of different power ratings as well as multiple solar controllers and panels while slowly upgrading my systems and buying new RVs. I wasted a lot of money by not thinking ahead about what I really wanted. I explain this in  “The Rabbit Hole” section below. Following is just a brief explanation. 

I started with a 300Ah lithium battery, a 1000W inverter, and a 600W solar array. 3 RVs later and now I have 600Ah of lithium, a 3000W inverter and 965W of solar. Through these changes, I have used GoPower, Renogy, Xantrex, and Victron. Each brand is good, however, the quality and the ability of each component to communicate with the others sets Victron above the others. If I had known where I would end up with my RV’s energy system I could have saved a lot of money. I guess that I learned a lot in the process. My hope here is that I can share what I learned and help you get started, as well as, help you not waste money. 

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The Components- Battery, Inverter, Charger, Solar panels, Solar controllers, Wiring, Monitoring equipment, and Generator. 

Whether you decide to go all out or stay small, I believe that the battery is the most important place to start. This is why, no matter what your set-up is, your capacity to supply energy to your RV will depend on the battery.  Yes, solar panels will supply power but this only works when the sun is shining. So, of course, nighttime is out but even on clouded-over days, your solar panels will provide drastically less energy.  If you get a good battery with a high capacity it will serve your needs through days when there is no sun.  I would recommend you buy batteries with the capacity to last for 3 days or more. 

So, how do you know how much energy you need for three days?  That is a great question. Honestly much of it is guesswork but you can figure out some of it with math. We will look at a few scenarios. Say you have a 100Ah (amp hour) battery.  This will deliver 100 amps for 1 hour hence 100Ah (Amp hours).  My 600Ah battery will deliver 600 amps for one hour.  Back to the 100h battery, it will also deliver 200 amps for ½ an hour. Note, twice the current = ½ the run time. It can deliver 50 amps for 2 hours. Again note ½ the current for twice the time. How long will it last if it only draws 5 amps?  It should last for 20 hours.  5 amps is not a lot but if you are not a heavy energy user this could last a long time. Here is an applicable example of how to use this. Let's say your 12V refrigerator uses 15A while it is running. If it ran constantly, using your 100Ah battery it would run for 6.67 hours. (capacity divided by the current = the time) 100Ah/15A=6.67h. So here is where the guesswork comes in. Will the refrigerator really be running all of the time?  What percentage of the day with the refrigerator actually be running? This depends on multiple variables like, how full it is, what temperature it is set at, the temperature of the RV cabin, etc…  Furrion estimates the refrigerator will use 1080Wh/day. For the record, this shows that in their test, it was on for 8.18 hours during a 24-hour period or about ⅓ of the time. 

 In simpler terms, this is 90Ah at 12V. In other words. A 90Ah 12V battery would be drained after 24 hours of running the refrigerator. Of course, we have other variables like solar, recharging the battery, and other components draining the battery. 

Just for a minute, I want to talk about the solar that comes stock with many post 2020 RVs, for example, our Grand Design 226RK.  It has a 165W solar panel. Theoretically in perfect conditions, this should be able to recharge about 65Ah back into the battery in a day.  Again, so many variables. This calculation is based on 165W, for an average of 5 hours in a day = 825Wh. For a 12V battery, 825Wh is just over 65Ah returned to the battery or used elsewhere in the RV’s 12V system.  So, sadly, the stock solar panel is theoretically, generally not enough to maintain the 12V system, especially one with a 12V refrigerator. 

Okay, back to the battery, now we know we will need more energy than just the solar to keep the RV happy for a sustained period of time. As I said before, the best place to start is with the battery. Of course, the larger battery you have, the more energy it will hold and hence the longer it will last. One other consideration is that the larger a battery bank is, the more current can be pulled from the battery.  This is important to know because if you decide you want a big 3000W inverter, you will need a battery that can handle 250A sustained. If you are not using an inverter you will not likely ever use more than 30A at a time from your battery.  

So what battery do you get?  Your best choice by far is Lithium Iron Phosphate.  The advantages are many. For example, this chemistry lasts 10 years, it has a higher voltage than other chemistries, it can be discharged to 90% of its capacity, and it can handle high currents both during charging and discharging. Also, it does not release gas so it does not need to be vented.  So what’s not to love?  The price!!!!!  These are not cheap.  However, If you plan on using your RV more than just a few weekends a year or know you will be off grid, they are worth the price. We have 2- 300Ah Amperetime batteries and are very happy with them.

But, if you do not want to spend the money to get a lithium battery or 2, there are other reasonable options. 2-6V lead-acid golf cart batteries in series will give you the most capacity of the lead-acid or AGM batteries category.  You can also run 2 or more 12V batteries in parallel. We could spend a lot of time discussing battery options but I would rather keep this section short. What is most important to know about lead-acid batteries is that you can only really discharge them to ½ their rated capacity. Going below this damages the battery.  AGM batteries can be discharged a little more but in my opinion, if you are willing to spend the money on an AGM, just buy a lithium battery. 
 

Do I Need a Different Battery Charger?

One of the most common questions I hear after someone upgrades to a lithium battery is, “Do I need a new charger?”  The answer is “Yes”.  But only if you are upgrading to lithium.  The 226RK comes with a Progressive Dynamics 3-stage charger. I think it is 50A or 60A.  Either way, it is a good charger. Do not worry about upgrading the charger if you are not upgrading to lithium. If you are upgrading to Lithium and an inverter, I would recommend buying an inverter/charger combo. I have used the Xantrex Pro 2000 and the Victron Multiplus 3000. 

This may be jumping ahead a bit but it fits well here. Our RVs run their 12V systems off their converter and battery.  The converter is basically a battery charger that converts 120VAC to 12VDC. When plugged into shore power, it supplies the RV’s 12V system with power and uses the battery as a buffer or charges the battery. So thinking ahead, having a charging system that can charge the battery as quickly as possible is good! My Multiplus will charge at 120A. This will charge my completely drained 1200Ah battery bank in 10 hours.  Why am I mentioning this now?  Because, if I have a large enough battery bank to last me a few days or even just one day, I can plug into shore power and recharge in a short time. Ideally, I could forget about installing solar.  I could just run my generator a few hours a day and recharge my batteries. If I miss a day, that’s fine too. Tomorrow I just run the generator longer. Many parks these days have generator hours in 2+ hour blocks 3 times a day. This keeps people from running their generators all day long. It is important to note that lead-acid and AGM can not be charged as fast as lithium without damaging them. 

Do You Need a Generator?

Again, there are so many variables so the answer is “it depends”.  Personally, we always carry our generator “for just in case” situations. Recently during the winter, the sun was low, the sky was cloudy and over 4 days we brought our batteries down to 20%.  One more day like that and I would have used the generator.  Also, If we are off grid and need to use our air-conditioner, I will use the generator.  I have enough power to run my A/C off my batteries and inverter for a short time but I have never done it. I have installed a Soft-start that lowers the startup current of the A/C. Even though, a locked rotor in the A/C could draw up to 60A at 120VAC.  That is 7200W.  That’s over twice what my inverter is rated for. Thankfully, most inverters have a start up rating that is sometimes double it's sustained rating or more. Our generator is only used for the A/C and emergency recharging if we need it. This is only because we have an inverter.  A few years back, before we had an inverter, we were in Smoky Mountains National Park.  We had no electric hook-ups and generator hours were after our morning coffee hour. So we put the coffee maker in the truck, drove down the road, started the generator, and made our coffee.  This became a routine. Yeah, I know we could have done pour-over or a myriad of other things but we were stubborn.  Next, we decided we needed an inverter. That was where the rabbit hole began!  

Do You Really Need an Inverter?     Or…. Why You Should Give Up Coffee. 

Down the rabbit hole, we go! Right after that trip, we bought a Flagstaff E-pro 19FD TT with a 1000W inverter! Humm, our coffee maker was rated at 1500W.  It was a good coffee maker!  So off we go looking for a 900W coffee maker.  Found one!!!  Oh, now our battery is not lasting.  Okay, let’s buy a lithium battery. Ouch, pricey!!  Screw it, we are going for it.  We bought a 300Ah Amperetime lithium battery. It had great ratings and the price was good. Better than buying 3-100Ah batteries. Wait, now our solar is not enough to charge this big battery.  Hey I know, let’s install another 600W of solar on the roof. Oh, now I need to buy tools to make solar connectors.  Darn it!  Now we need a bigger solar controller. We bought a Renogy Rover 35A MPPT controller. So…. here we are all set up but, the 1000W inverter is not enough for the new air-fryer. Now, I buy a Xantrex 2000 Pro inverter/charger.  Shoot, these battery cables are not large enough for the new higher current.  I buy new battery cables but now I need a heavy-duty crimper to install the lugs on the cables. All was good until we decided to buy a new RV… and then another.  This one, the 226RK is our last RV!!!  Right????  Long story longer, we now have the 226RK set up with 965W of solar on the roof and 300W of folding portable panels, 4-300Ah batteries (1200Ah), 3 Victron solar controllers, a DC-DC charger, a Victron Multiplus 3000 inverter/charger, a Cerbo GX monitor that tells me everything I need to know and feeds that info to the VRM web so I can analyze all of my data. A geek’s dream! This is an expensive coffee maker!!!!  But, I can make popcorn too!

However, with the equipment we have, we live life as if we are always plugged in. I never need to reset the clock on the microwave unless we change time zones. As soon as I unplug from shore the inverter immediately kicks in and we resume having 120VAC on a perpetual basis. This inverter will also supply extra power from the battery when I am on shore power. For example, say I am running both air-conditioners. If they both kick on at the same time it may draw a lot of current from the shore.  I have my inverter set so if I draw more than 30A, the inverter will take power from the battery to support the extra power needed by both air-conditioners kicking on at the same time. I don’t need to be plugged into a 50A service to run both A/Cs.  I can now use a 30A service. 

One last thing about inverters. I recently read a Facebook post about someone who needed a CPAP machine at night. They hoped to use a generator.  If you need medical equipment that uses 120VAC there is no question, buy a high-quality pure sine wave inverter. Over the years, I have had generators quit, fail to start, or run out of gas.  The inverter always starts.  It makes no noise so it does not bother the neighbors. I have never poured gas all over my hands and feet using it either. An inverter does not have to be a big expensive piece of equipment. A small properly sized one will do. All 120VAC equipment has a stamp/sticker that tells you either the watts or amps. If only the amps are given, just multiply by 120V to get the wattage. 

Do You Need Solar Power?

Solar power is great. It is quiet and it is free. Well, sort of free after you spend a bunch of money building the solar array.  I want to answer the question: “do you need solar?”. I would say “no”  Solar is great to have and I would never want to give it up. But, as I stated before, the battery you have is most important. Let’s look at it this way.  There are only 3 ways your battery is going to get charged. 1. Plugging into shore power. 2. Plugging into a generator. 3. Solar.  Your RV is composed of two separate electrical systems.  It has a 120VAC system that runs the converter/charger, the microwave, air-conditioners, coffee maker, etc….  It also has a 12VDC system that essentially runs off the battery.  This runs the lights, water pump, awning, slides, vent fans, etc… So if you are plugged in like options 1 & 2 above, either shore or generator, you will have the benefits of both the 120VAC and the 12VDC systems. During these times you do not need solar.  Your battery is already getting charged. So when do you NEED solar?  You need solar when you will not be able to charge your battery to the capacity you need AND you will NOT have any other way to charge your battery.  It is important to note that solar will only charge your battery, it will stop charging when it is full. In other words, the battery is the storage bank for any solar energy you acquire. When the battery is full the energy has nowhere to go so it is pretty much wasted.  When the sun is low or it is cloudy your solar will NOT supply the power it is rated for.  Lastly, when it is dark your solar panels have nothing to do but wait for the sun to shine again.  

So, why would you want solar?  I already explained the benefits of having a good battery, a good charger, and a generator.  Honestly, it really is all you need. Yeah, but it’s not, especially because solar is so easy.  No generators to start. No cord to deal with. No noise. No pollution.  Also, your solar panels will allow you to preserve your charged batteries during the day by supplying power to your fans, refrigerator, water pump, and lights. So, do you need solar?  No. There are other options. However solar is the best option. If money is tight, hold off on your solar array.  Spend your money on a good battery system, a good charger, or even a good charger/inverter combo. Buy a cheap generator that can charge your system during the day so you can use the power after hours. Heck, buy a good generator because it will still be an essential tool even if you have an excellent solar array. I promise you will end up sitting in the RV for days wishing the rain would stop at least once in your RVing career. 

How Much Solar Power Do You Need?

In an ideal situation, you would like to have 3 times the watts of solar panels as you have Ah of battery.  For example, if you have a 100Ah battery, you would want 300 watts of solar power. Keep in mind that this is ideal.  In my case, I only have ½ of this.  I have 600Ah of battery capacity so I would want 1800 watts of solar. I don’t have that but I “want” that.  I don't have room for it.  Also, don’t look at this backward. Just because I only have 900 watts of solar does not mean I can ONLY have 300Ah of battery.  Heck no, to quote Tim the Tool Man, “ugh ugh More Power!!”  However, this is why my system would not recover after those 4 days of low sun, clouds, and rain. But, if I had only 300Ah of battery I would definitely have needed the generator. 

A Battery Monitor

Lastly, I would suggest a shunt-style battery monitor. This amazing tool tells you what is happening with your battery.  It tells you whether a charge is going into or out of your battery. It also tells you how much charge is going in or out. It tells you how full your battery is.  Amazon has cheap ones.  They work but you need to fiddle with them. These tell you voltage but they are not good at recording the precise state of charge. I have installed 3 of these. They are okay for the money but I highly recommend the Victron shunt. Even if this is the only piece of Victron equipment in your RV, you will be glad you spent the money on it. Victron sells a 500A shunt that has a Bluetooth app.  It sells for about $130.  It is well worth it.  This gets wired between the battery and its negative cable. The app tells you current in, current out, voltage, battery percentage as well as history. This shunt will also communicate with all the other smart Victron components. The 226RK does come with a shunt-style battery monitor. You can continue to use this.  However, if you make changes to your system, make sure it is wired directly between the battery's negative terminal and everything else. (note to self look up the rating of this monitor)