RV air conditioning on batteries and solar. Can you do it? My goal is to be electrical energy independent, which includes air conditioning on batteries and solar panels. I can run my RV air conditioning from my batteries all night long. I installed a large battery and solar electric system. I can run my RV air conditioning from my battery bank and recharge the batteries simultaneously from my solar array. The RV air conditioner runs on batteries, and solar replaces (most of) the electricity that the RV consumes, including the air conditioner.
Original Article published April 2021
This article includes almost five years of data and explanations. I started writing it down in 2020, including updates from every year since then. It is no longer just an idea; we have the answers. Here are the details of how we operated before we had our big lithium battery bank and solar array. RV Electricity the Hard Way, without solar or lithium
Notes pertaining to the pictures: Most of the pictures in this article are decorations. I’m sorry, but it is hard to photograph air conditioning and impossible to photograph the electricity needed to run it.
Everything you need to know about to run your RV air conditioner on batteries and solar.
Table of Contents
Frequently Asked Questions!
Sorry if you get the same answers more than once. Sometimes, similar information will be provided for slightly different questions to answer each question completely.
Can you run your RV air conditioner only with batteries and solar panels?
The answer is yes, you can—if you have a big battery bank and a large inverter. Then, you have to install a solar array big enough to replace the energy that the air conditioner consumes. I also had to rewire my electrical panel so that my inverter would supply the electricity from the batteries to the air conditioners.
My system requires a large inverter. I have friends with direct-current (DC) air conditioners (almost experimental models) that don’t require an inverter. Because this design is more efficient, they can run their air conditioners longer than I can from the same battery power. My big inverter wastes about 10% of my available power and converts the wasted electricity into heat.
Can you run an RV air conditioner only on solar panels? (without a big battery bank)
Not in my system. My solar panel is wired to recharge my batteries, but it is not wired directly to the inverter, so I can’t run my air conditioners directly from the solar panel. This wasn’t my design goal because I want to run my air conditioner when I want it, including after sunset. This won’t work without a big battery bank.
Is it practical to install an RV battery bank big enough to run an air conditioner?
For me, the answer is yes. For you, the answer depends on your priorities. For me, installing a battery system big enough to run my air conditioner is practical. I wanted to run my air conditioner at night when I was sleeping, so it was critical that I have a battery bank big enough to accomplish this goal. The battery bank also allows me to run my RV for two and a half days without any additional electrical energy when I don’t need my air conditioner.
How many batteries does it take to run an air conditioner?
I can run one of my air conditioners for about one hour on each one-hundred amp-hour lithium battery. I have nine one-hundred amp-hour lithium batteries. So, if I did this, my batteries would be empty after nine hours. I could make this better in several ways and have friends that have more efficient (smaller RVs) and more efficient electrical systems that can run their air conditioners longer from each battery.
Can you run your air conditioner on your solar without depleting your battery charge?
Not for my system. I will explain this next. Running the air conditioner in the afternoon without depleting the battery charge was a hopeful goal, but I have to say that I didn’t completely accomplish this goal. If I were to increase my solar array size by perhaps 30%, then I am pretty sure I could do this. Part of installing more solar panels would provide additional shade on my RV roof.
How many solar panels does it take to run an air conditioner?
The answer for my air conditioner is more than 2000 delivered watts per hour. I have 1800 watts of solar but can only deliver 1400 watts. Solar panels are only 100 efficient in a laboratory. On an RV roof, they will never deliver their full rating. For many RVers, the limit is roof space. For others, the limit is money. For me, the answer was no. The reason it is not is because of diminishing returns.
Additionally, I still have my RV generator, so I have options.
My first 900 watts of solar panels provide most of the energy I need on a typical day. This includes running my refrigerator all day long. My second 900 watts of solar panels means that I usually can fully recharge before noon after a typical night’s energy use. Then, in the afternoon, I can use the extra energy and live without any concerns about running out of electricity. When the sun goes down, I almost always have a 100% charge on my battery bank. Assuming that I didn’t need air conditioning at night, then I would have depleted about twenty-five to forty percent of my battery charge before the solar array started charging the next day.
I had an advantage from the beginning.
My RV initially cost less to install a huge battery bank and solar panels than many similar RVs. When I installed a massive battery bank, I already had a very capable Magnum Inverter/ Charger. I have plenty of battery power, and I can run one of my air conditioners on batteries, starting with a full charge, for about eight hours. I also have a large-capacity generator that can run both of my air conditioners and recharge my batteries simultaneously.
Is it hard to run your air conditioner from your solar?
The simple answer is that to get solar to work, you must park the RV in the sun. When you park your RV in the sun, your air conditioner must work much harder than if you park in the shade. If you park in the shade, then the solar panels won’t work. It is better to park in the shade, run your air conditioner from a generator, and simultaneously charge your batteries so that you can run your air conditioner from your battery bank at night when you are sleeping.
Having a large battery bank and a large solar array isn’t just to run the air conditioner; it’s to supply all my electrical energy needs when I don’t need it.
Could I build an RV that could operate completely on solar?
Not if you include driving the RV on solar only.
I am convinced that I could achieve everything other than driving in a carefully designed RV. The design would have to have this as a goal from the beginning. One of the design criteria would be to have a completely clear roof. RV roofs typically have lots of obstructions, and that makes covering the roof with solar panels very difficult. I have an RV that balances travel with energy independence and makes travel easy. My RV also places a premium on space and comfort.
How long can I run my air conditioner from my battery?
I have a big battery bank and a big enough inverter. I can run my air conditioner all night when I sleep (more than 8 hours per night). That makes me happy and makes me much more capable than almost every other RV. The solar array is great, but it is not good enough to run my air conditioner continually while it is sitting in the sun.
How do my battery and solar work to run my RV?
The battery powers the inverter, which runs the electrical needs. The solar recharges the battery. The key is to have a battery bank that is big enough. Here is a link to a description. Why do we have a Hybrid Mongrel Battery in our RV? This past fall, we replaced our lead-acid batteries and made an additional electrical remodel. Here is a link to our new configuration. Can one lithium battery replace four lead-acid batteries?
Here is a link to the description of my battery bank. Make sure that you understand the meaning of an electric bucket. It is a very important part of this issue. Massive Electric Bucket
The next step is to install a large solar panel array. I wanted it to be capable of creating enough electricity to “run” the air conditioner with enough extra electrical energy to recharge the batteries at the same time. When I am not running the air conditioning, I aim to dump about 100 amp-hours of electricity into my battery as fast as possible. Installing our Zamp Obsidian Solar Array
I can easily hit 500 amp-hours per sunny day of charging. Sometimes, on a long summer day, I have created more than 1100 amp-hours in a single day. The problem is that the air conditioner can easily use everything the solar array can put out. Some people have suggested that we have too many solar panels or that they were wired incorrectly. Here is a link associated with that question. You have too many solar panels on your RV!
It is not my design goal to run my air conditioning on batteries and solar indefinitely, especially in the south, in the summer, with solar power alone. I don’t have enough roof space to accomplish such a feat. However, I can easily achieve my goal of occasional use—my occasional use means all night long when necessary.
The details of RV Air Conditioning from Solar
Air conditioning on solar is a holy grail for RVs. The statement “from solar” is incomplete. You don’t run air conditioning on batteries and solar; instead, the solar charges the batteries. The batteries deliver the energy to the inverter, which in turn runs the air conditioner.
Running the air conditioner directly from the solar is a non-starter because you don’t only want to run the air conditioners just when the sun is shining. Rather, you want to run the air conditioners when it is most important for you to have a more comfortable RV. For me, this means being able to run my air conditioner at night without the benefit of sunshine.
When do we use air conditioning on batteries and solar?
When we are sleeping.
Sometimes, when we are boondocking, it is quite warm at bedtime—air conditioning would be great, but it would be a direct drain on the battery.
When generator use is restricted.
While camping in Death Valley, we got caught by the “generator police” at 7 p.m. because our generator was still on (we were standing outside). It would have been so nice to have air conditioning that night. Obviously, this situation was repeated many times before we put in a large battery bank and solar panels. Since then, I can’t think of any time this was a problem.
Here is a link to that story. Death Valley National Park
When driving.
Another time when air conditioning on batteries and solar is great is when we are driving. We typically drive about one or two hours in the middle of the day. While we are driving, we can run our air conditioners to keep the house cool and make the RV more comfortable during our travel days. Usually, we only use our dash air conditioner when driving, but occasionally, we turn on the solar and battery-operated air conditioner.
Assuming we are traveling during the daytime (we always travel during the daytime) and assuming it is sunny (not always the case), the solar would still be charging the battery while we are driving. At the same time, we can run our air conditioning on batteries and solar. We don’t use our engine alternator to recharge our lithium batteries. In this case, we wouldn’t need the solar. We don’t use our engine alternator because we have solar.
In the afternoon.
We could run the air conditioning on batteries and solar in the afternoon, which is exactly when it would be most appreciated. If the battery is full or nearly full, then the air conditioning can run while charging from the solar. If the battery needs a charge, then starting the generator would run the air conditioners and charge the battery from the generator and solar simultaneously.
Using our RV Air conditioning as a heat pump
My air conditioning units are heat pumps. This means that since I can run the air conditioners, I can, if I desire, also use them to create heat. Heat pumps are far more energy-efficient than my electric room space heater. So I could create electrical heat using the batteries. I don’t have any reason to do this because I also have two propane furnaces that are way more energy-efficient than any electrical heat source.
So how much electricity does an air conditioner consume?
It depends on how hot it is and whether I am sitting in the sun or the shade.
RV air conditioners consume about 900 watts (each) per hour to run. (2021 edit: I was wrong. My air conditioners can and frequently consume over 900 watts of electricity. I have real-world test results both while parked in the shade without the sun hitting the solar panels and when sitting in the sun). In the same conditions, with a big solar panel array, air conditioning needs can be lower because the solar panels shade my roof.
Note about starting an RV air conditioner. (Our air conditioners used to pull much more than 3000 watts during start-up. Here is a link about how to tame the start-up spike. Micro-Air EasyStart
So, since each 100 amp-hour battery holds about 1200-1350 watt-hours of usable energy when full, and assuming the battery is full when I start, each battery can run one air conditioner for 1 to 1.5 hours, depending on compressor cycling.
Assuming I had the solar running at full tilt in the same conditions, I would be producing around 1400 watts per hour (1400 watts per hour assumes no shading and ideal conditions). So, easy math says if I am consuming 900 watts per hour (2021 edit: more like 1500 watts per hour) and making 1400 watts per hour, I can charge the batteries at the same time as running the air conditioner.
(edit 2023: You may have noticed I said 900-1500 watts per hour, which is way less than the 2017 watts of electricity that my air conditioner is rated at. The difference is that the compressor does not run continuously but rather cycles on and off. This was not true in Las Vegas in August 2017, but that was an extreme condition with temperatures of more than 110 degrees after sunset. At these temperatures, the compressor was on all the time.)
These calculations will not be replicated in real life except during ideal conditions. There are too many variables. One tree shading part of one panel can affect the output of three panels. Shade kills the output of solar panels dramatically.
Before we installed the solar, I hoped that the solar could run one air conditioner at full blast with no net drain on the battery. (edit 2022: this proved not to be correct. Almost always, even with direct sun on the panels, there will be a net drain on my battery.)
It also depends on the wind.
When it is windy, which is always the case when we are driving, then the air moving across the skin of the RV cools, and the exterior RV skin temperature is always cooler than when it isn’t windy. The air conditioner doesn’t have to work as hard as air conditioning is easier.
Additionally, solar panels benefit from the wind and produce more energy when cooled. My maximum is still only about 1400 watts per hour, and this is easy to achieve with cool panels. Plus, when we are driving, we have the dash air conditioner running, which dramatically reduces compressor cycle time. So we run the rear air conditioner when driving.
My RV required an electrical remodel
When Tiffin designed our RV in 2008, they never anticipated that anyone would want to run the air conditioning on batteries and solar. It simply wasn’t on their radar. They were pushing the design when they included a residential refrigerator. To do this, Tiffin installed extra batteries and solar panels to help run the refrigerator. Anytime air conditioning was needed, the answer was to start the generator or plug into shore power. Air conditioning on batteries and solar was not part of the design.
Ninety-nine percent of RVs coming off the assembly line today in 2023 are still designed the same way or with less capable electrical systems than our RV had in 2008. This includes our previous 2013 Tiffin, which is electrically inferior to our 2008.
RV power math: 50 amp = 100 amps and 30 amps = 30 amps
This section pertains to plugging the RV into power at the campground. Just like your home, this service is supplied in alternating current (AC). Shore power or my generator feeds the “50 amp main” supply to the circuit breaker panel.
This supply is divided into two branches, commonly named red and black, as associated with the wire color. Both the red and black wires can supply 50 amps for distribution. Thus, when you have 50-amp service, you have two sources of 50-amp power. Thus, 50 amps = 100 amps of power. In my RV, and I would venture to say all RVs with 50-amp service, one air conditioner is on the red wire, and the other air conditioner is on the black wire.
When plugged into a 30 amp supply, then both branches share the 30 amp service and deliver the 30 amp to distribution. Thus 30 amps = 30 amps. The same is true for 20 amps. 20 amps = 20 amps
What we needed was a redesign inside the circuit breaker panel.
Here is a general overview. Alternating current electrical power comes into the circuit breaker panel from three different sources. The three sources are shore power, generator, or inverter. Shore power can deliver 100 amps (AC) of power to the circuit breaker panel. The generator can deliver 55 amps of power to the circuit breaker panel. The inverter from the batteries can deliver 27 amps of power. The 2008 circuit breaker layout would not allow me to run air conditioning on batteries and solar– so I rewired it.
One way you could wire the RV is to have a manual switch that selects the power source. Nearly all RVs with factory-installed inverters are designed with a transfer switch that chooses between the generator and shore power. Our default condition is that when the generator is on, it is the electrical power source.
Inverter power is delegated to a secondary role and is only used when the generator or shore power is off. This is accomplished via a sub-panel. The sub-panel is powered directly from the inverter when operating on battery power or from the shore power/generator, which is our power source. The power source would need to be from the sub-panel to run the air conditioning on batteries and solar panels.
Electrical flow in the circuit breaker panel
This is how my RV works—it is very likely that your RV does not work the same way!!! If you don’t understand it, don’t monkey with it.
Shore power or generator power enters the circuit breaker panel via the 50 amp circuit breakers (one red, one black) and energizes the red and black bus. From the red and black bus, part of the power (30 amp red and 30 amp black) is then routed to the inverter from a circuit breaker labeled “inverter out”… The power passes through the inverter and is returned to the circuit breaker sub-panel on the “inverter in” circuit breakers. (30 amp red and 30 amp black).
The sub-panel routes the electricity to the sub-panel circuits. Without the change to the sub-panel, I would never be able to air the conditioner on batteries and solar. I needed my air conditioners on the inverter’s portion of my electrical distribution.
If electricity from the generator or shore power is not available, then the inverter will convert battery power (DC) into (AC) power and supply the sub-panel with electricity to operate sub-panel circuits. My microwave and refrigerator operate from the inverter and thus will run with or without shore power. (assuming the batteries are full enough to operate the inverter)
Remodeling inside the circuit breaker panel
The circuit breakers that operate the air conditioners were on circuits only supplied by generator or shore power. Thus, the air conditioners could not operate from the inverter (even though the inverter was on and big enough). Because the air conditioners were not on the panel powered by the inverter, they could not be used.
Hence, to achieve air conditioning from batteries, I rewired the inside of the circuit breaker panel to move them to the portion powered by the inverter. Now, they can operate from the inverter.
RV power over allocation — caution
An older small house usually has a 200-amp (AC) power service. RVs almost always have a maximum of 100 amps (AC) service and, as outlined above, in many cases, have less than 100 amps (AC). It is easy to use more than 100 amps (AC) in an RV.
My re-wire creates a potential for an over-allocation of electrical power. I looked carefully at this issue; Tiffin had already over-allocated the electrical circuits on the sub-panel. By adding the air conditioners, I have increased the potential of turning on too many devices, thus tripping the circuit breaker and interrupting power. You cannot ask for too many amps simultaneously, or the circuit breaker will trip. So even though I am over-allocated, I am unlikely to trip my circuit breaker. The reason is that the items that could be used when operating on a battery are unlikely to be used when operating on a battery only.
Where are the power hogs?
My power hogs are the inverter (when operating as a battery charger), air conditioners, water heater, engine heater, electric space heater, convection oven/microwave, clothes dryer, hairdryer, and instant pot. The refrigerator also needs to be included in this discussion. It does not consume lots of power all at once, but it is a large power load and an essential item.
Of the above items, the only things I can never operate from the inverter are the engine and water heater. These items are only hooked to the main bus, not the secondary bus. I can only use them when hooked to shore power or when running the generator. I cannot run them powered by the inverter.
My power hogs that are able to operate when I don’t have external power are air conditioners, electric space heaters, convection ovens/microwaves, clothes dryers, hairdryers, and instant pots.
I will rarely use the air conditioners and convection ovens for battery power. I will likely never use the clothes dryer and electric space heater on battery power. (2022 edit: I was wrong. Sometimes, we run our clothes dryer from our batteries, but only occasionally when we have plenty of solar power. We also don’t hesitate to run the convection oven, hair dryer, or instant pot.)
If I attempt to operate too many of the power hogs simultaneously, I will trip the circuit breaker.
Important Items when on battery only
Used all the time = refrigerator. Occasional use = microwave and instant pot. Rare use = hairdryer and air conditioner. Almost never used = clothes dryer. Never used = electric space heater. (2022 edit: Sometimes, when we think we have shore power, we mistakenly run our electric space heaters from the batteries. We do this when shore power fails, and we don’t know if it has failed. It is very hard to tell when shore power has failed in our RV because, operationally, everything is the same. This results in our battery supply depleting in just a few hours.) Extended RV Dry Camping for twelve days on solar
Air Conditioning on Batteries and Solar Test Results
Air Conditioning on Batteries and Solar is very possible, but you have to know the system’s limits. Just because you increase the design’s abilities does not mean you are operating without limits.
Updated April 7, 2024, includes edits from 2021 and 2022, as noted
Can you run your RV Air conditioner on Solar and Batteries?
We have the test results. The quick answer is yes, you can. We have proved that it is possible. This update includes testing data with some surprises. These surprises are not always encouraging and show how hard this is and why it is this hard.
As I write these observations, we have been running our air conditioners from our batteries for five and a half hours over two different days. During monitored tests, we consumed 839 amp-hours of electricity. On average, this is 152 amps per hour, almost twice the consumption we expected. You might say that we found the limit by pushing as hard as we could. The pedal is all the way to the floor, and there isn’t anymore.
Running our air conditioners while driving
We first tested running our air conditioners, operating from solar and our batteries while driving in the middle of the day. The air temperature during the test was between 85 and 95.
The dash air conditioner was not working correctly (we didn’t know that at the time), and it was unable to keep up with the heat gain. The bedroom area in the back of the RV was also hot, but we did not run the air conditioner in the back during the test—simply because we couldn’t unless we had started our generator.
Had we been stationary, we would have had a less challenging test for one big reason: We would have covered all our windows to prevent sunlight from going through the glass. We were driving south when we ran our air conditioner from our batteries, which explains how hard the test was. The sunlight was streaming through our four-by-eight-foot windshield and the driver’s three-foot-by-four-foot window for the entire test duration.
Since we were driving, our air conditioner had constant airflow and wind moving across the unit, which increased its efficiency by a small amount. However, given the design of the air conditioner, the airflow did not go through the condenser coils, which would have made a big difference in aiding heat transfer.
Also, to make the test hard (and because I am cheap—even with electricity from my batteries), we waited until the RV was uncomfortably hot before turning on the RV air conditioner from the solar and batteries.
We also left our refrigerator on during the test, just as we would have had we used our RV in normal conditions.
A big problem is the inverter overhead.
Our inverter is a Magnum 2812 inverter/converter, and its maximum sustained output is 2800 watts. We pulled up to 2680 watts per hour during the test. This was a combination of the air conditioner, refrigerator, and inverter overhead. Converting DC electricity to AC electricity in the inverter accounts for 10% of the energy used during the test.
Thus, you can blame the inverter for the 268 watts of energy consumed per hour at this data point. The refrigerator alone, while cooling, consumes more than 266 watts of energy per hour (peaking above 400 watts occasionally). These numbers include static (24 hours a day) inverter overhead of about 23-40 watts). Even when doing nothing, our inverter consumes about 23 watts per hour. This is inverter overhead. It is Something I understand now that I have experienced – it is now very real.
This means that producing the energy to run the air conditioner comports with its maximum design draw, which is about 2017 watts per hour. The air conditioner will operate at 95 degrees on the high setting. (Energy consumption of air conditioners increases with increasing outside air temperature, as illustrated in this table from the Coleman operations manual.)
Air conditioner energy use at different temperatures
According to the above graphic, each five-degree increase above 95 degrees will increase air conditioner power consumption by about 120 watts. Air conditioner manufacturers are careful not to provide the exact numbers for increased energy consumption based on condenser temperature.
Other individual data points (all include inverter overhead)
- Front air conditioner on high – driving – cooling, refrigerator on – cooling = 2350-2680w
- Front air conditioner on high – driving – cooling, refrigerator on- not cooling = 2124-2171w
- Rear air conditioner on high – cooling, refrigerator off = 2050-2086w
- Rear air conditioner on low – cooling, refrigerator off = 1963w
- Refrigerator – cooling two computers and monitor on = 358w
- Refrigerator – cooling one laptop on = 300-353w
- Refrigerator – cooling, nothing else on = 266w-426w
- Rear air conditioner – fan only, refrigerator off = 254-286w
- Refrigerator on – not cooling, everything else off, = 87w
- Nothing on except inverter = 21w
These are individual data points, not measurements over a period of time. Also, data points taken while driving had different conditions than those taken when stationary.
Internet-based False Hope
There is a lot of information available on the Internet that, for me, created some false hope about how long I could run an air conditioner off my batteries.
Issues associated with operating your air conditioner from battery power
First, I have a very large air conditioner. (15,000 BTU) Second, I tested in a challenging situation. Third, I did not correctly anticipate inverter efficiency. Finally, you don’t just run an air conditioner — you have to run other things besides the air conditioner.
I will assume that others stating they can run their air conditioners at numbers well less than my measured 2000+ watts per hour must have smaller air conditioners. They also probably have less space they are trying to cool than I have. Perhaps they also have a different color RV that would reflect more heat (polished silver is best), and maybe they have a better-insulated RV.
I will also assume that others are trying to run their air conditioners in a much less challenging environment. If you want air conditioning at 80 degrees in the shade, the answer will be much different than in the direct sun at 95 degrees.
I have already addressed my oversight of inverter efficiency in the above test results analysis.
We did not turn off our other loads, just so that we could run our air conditioner.
One of our future tests will be at night when sleeping—we should be able to go all night long. It depends on how much of our battery charge we use before we go to bed. (Edit 2022: This worked great last winter in Key West. In our campground, while dry camping, we were the only ones with enough power to operate our air conditioner from our batteries while we were sleeping. Here is a link to the results. How did we live on Solar when at Key West?
Limits to all solar electric systems, including our solar array
At first, operating our air conditioner with solar and batteries previously was an incomplete test… we don’t have solar, so we did battery tests to determine if the proposed solar would accomplish what we wanted it to do. Obviously, the possible consumption of 2680 watts per hour from the battery cannot be offset by less than 2000 watts of solar.
The inverter overhead associated with the 2680-watt load will still be required with solar. If we could get 2000 watts from solar, we could produce about 2/3 of the consumption. Perhaps this argues for a bigger solar array, but I don’t think so. We expect the solar to carry most of the load — not all the load.
Now that we have a fully functional solar array, and we knew this before installation, I should point out again that our solar array is almost always oriented in a fashion that inhibits it from performing at or even near laboratory specifications. We limited our expectations with this assumption. We are lucky to extract 75% of the laboratory-specified ratings. You will probably have the same result unless your solar array tracks the sun. This is one of the reasons we installed eighteen hundred watts of solar panels but only allocated and anticipated fourteen hundred watts of delivered energy.
Over temperature in your battery/inverter compartment is a real possibility
One of the surprises, other than how much load the air conditioners place on batteries, is how hard the inverter was working to convert the DC power into AC power. In the future, we might decide not to run the air conditioners while we are driving because this puts a large load on the inverter, creating heat that we currently don’t have a way to vent.
The maximum temperature we saw in the battery compartment was above 100 degrees. The temperature sensor is about 9 inches off the floor – attached to the battery. Our inverter is attached to the ceiling. This means that the temperature at the inverter level was higher than the temperature sensor. When we saw the temperature rise, we ended the test. Heat is not good for inverters or batteries.
Airflow in the battery/inverter compartment
Airflow in the battery compartment is much more restricted than I had thought it was. When the temperature hit 100F, I turned the air conditioner off. This is a large compartment (with lots of junk), and I didn’t think it was this airtight—I guess I was wrong.
When the compartment temperature hit 100, it was 95 outside, and we were getting close to Las Vegas. The reason the temperature was rising was that the inverter was producing heat. Remember the 268 watts of inverter overhead? The inverter was converting this waste into heat while converting DC to AC.
This is going to lead to another modification. I will install some vents near the inverter to help prevent high temperatures. Of course, in the winter, I will need to close the vents to keep everything warm. I am also thinking of a scoop that would provide some ram air cooling to the inverter compartment. This would also need to be closed in the winter. (Edit March 2023: I have yet to install these vents, and the location that I have chosen wouldn’t work when driving. So, instead, we open our compartment doors to increase the airflow inside the compartments. )
Most obviously, we are going to have to figure out why our dash air conditioner is not sufficient and why we need to turn on the roof air conditioner. I know it is common in big RVs to run the roof air conditioner, but I am not yet ready to accept this as a requirement. (Edit 2022: Our dash air conditioner was completely nonoperational. During our last visit to Red Bay, we got it fixed.)
I started writing this post right after we rewired our circuit breaker panel to enable the test. So, unless something major changes, I will consider this subject covered.
It is important to measure rather than guess
How do you measure how much energy is coming out of your battery? Check out this article about what I think is the most critical component in an RV electrical system. Battery Monitor
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Links
The critical component for air conditioning from batteries and solar
Air conditioning from batteries and solar would not be possible without adding this one critical component. This component tames the spike that happens when the compressor starts. Here is my link to installing my Micro-Air EasyStart.
This is what we used. We do not get commissions on the links; they are provided only to help our friends.
RV Electricity the Hard Way, without solar or lithium
Why do we have a Hybrid Mongrel Battery in our RV?
Installing our Zamp Obsidian Solar Array
You Have Too Many Solar Panels On Your RV!
Extended RV Dry Camping for twelve days on solar
How did we live on Solar when at Key West?
Magnum 2812 Inverter Converter
Ten Lithium Battery Myths and Answers
As discussed above, I started testing RV solar and batteries five years ago. I started writing this article in 2020; some comments were from a previous edition released in September 2020. Over the last three years, I have edited this article annually to provide the most up-to-date information.
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Not engrossed in the solar stuff but ❤️ The sunset!
The refrigerator is consuming way too much power. You need to look into that.
I just put the kill-a-watt on the fridge to collect more data. Since the compressor cycles on and off, the peak draw isn’t as important as how much the fridge uses over time.
So I have the following set-up:
2 x Victron Energy MultiPlus 24/3000/70-50 Inverters
8 x Lion UT1300 LiFePo4 Batteries (420Ah @24V)
8 x 200W Hi Tech Solar Panels w/tilt brackets
1 x Victron MPPT 150|100Tr Solar Charge Controller
1 x Victron Cerbo GX
1 x Victron GX Flat Panel Screen
1 x Victron BMV 712 Battery Monitor
2 x Victron Lynx Distributor 1000A DC
2 x Victron Orion-Tr Smart 12/24-15A DC-DC Chargers
2 x Victron Energy Orion 24/12-70 DC-DC Converters
With our set-up, we are able to run our 13.5K AC unit and it draws about 65A (@24V), this is just a bit more than the solar system can generate at “Solar Noon” and with the engine running and full sun we actually can put about 15-20A back into the batteries when underway. After the sun goes down and with the refrigerator running we use about 80A, so that eats up the 420A pretty quickly. This summer we were able to run the AC for a couple of hours in the evening, watch TV and everything else living pretty normally and we were waking up with anywhere from 30 – 45% remaining………We were full charged typically by 1-2PM with good sun.
Now while driving this is a different thing………..we run the AC in the rear and the dash air, don’t run the front AC. This keeps the rear compartment where the engine, batteries and inverter(s) reside, plus of course being ducted throughout our 36′ DP.
Thanks for the great article!!
I found the same problem with my old inverter (Xantrex Prosine) as on a 100 degree day it would overtemp and shut down after 1- 1.5 hours of use. This past summer I replaced it with a Giandel 4000watt inverter (standby on power is 6 watts)- it’s super efficient and has massive cooling capabilities. Still if running the air conditioner more than a couple of hours we just start the generator. Everything else easily runs off the solar 1280 watts and batteries (675 ah of LiFePo4). When boondocking we save about 2 kWh (170 Ah) a day by running our fridge on propane. It’s definitely a learning curve to learning to live with battery and solar power!
Wow, what a great picture.
Wow!, I never thought we can run our AC using batteries, I will definitely give it a try. This blog is really a worthy one. Thanks
Running an air conditioner from a battery is possible. The question is it practical?
Having a big enough solar array to keep up with the needs of the air conditioner is difficult… too hot, not enough insulation, and not enough roof space. If we added an additional 900 watts on the roof we could break even on solar input versus on air conditioner.
We have used our air conditioner, from our battery, starting at bedtime until the next morning. When we awake the next morning on comes the generator to get ready for the next day.
Like many RVers, I too, have discovered that almost always, you WILL run the roof a/c when driving. One of the reasons that I chose a Country Coach RV was their use of an 18,000 btu-rated dash a/c, the largest output available at that time.
But, it’s still inadequate & REQUIRES that I run the roof a/c to stay comfortable when traveling in the warmer months. The large interior volume of class A RVs requires additional cooling capacity and is probably why I have seen some RV with drapes installed behind the front seats.
Almost every RVer that I have talked with run their generator & at least one rooftop a/c while driving. Personally, I don’t see any advantage in running the rooftop air conditioners from batteries while driving. I use my battery capacity to run my rooftop a/c in the bedroom area for a few hours in the evening before calling it a day!
We almost never run our roof air conditioners when driving. Our dash AC seems to do just enough. We don’t require a curtain behind the driver’s seats.
We are not against it we just haven’t needed it. Our system allows us to run the AC from batteries but we don’t do that very often.
Like you, I also use the battery to run the AC all night if necessary when we are sleeping to keep the temperature cool enough to sleep
Another former “nasal radiator” here….mostly WestPac including a tour on the Midway after her blister mod flying Hornets. (Call sign was BUFLO)
I’ve crossed paths with your blog on solar and lithium somewhere in the past while doing my initial research….and I’ve somehow incorporated quite a bit of your same thoughts and considerations without consciously knowing they originated with you.
My system is just about done being field-tested now and I will be making my wiring runs and component locations more permanent soon. I went with a Magnum Energy MSH4024M and built my battery bucket @ 24VDC using two EG4-LifePower4 Lithium Battery | 24V 200AH in parallel to provide 10KWH of storage…..on the roof is 1,640 Watts of PV solar connected series / parallel to work at just under 100VDC / 22Amps down to a Victron MPPT 150/70 solar controller. My house DC is hybrid in that I retained a single “placeholder” flooded 12VDC fed from the 24VDC LiON battery bank via a Victron Orion 24V|12V-30A buck converter charger to support normal 12VDC house loads and provide a battery boost capability for the chassis battery if needed.
As far as the rig knows, nothing has changed for any of the house wirings at this point….the 12VDC loads remain as from the factory, and the AC panel hasn’t yet been modified.
My plan for the roof A/C is to insert a transfer switch in the source to the roof A/C that will prioritize between main panel AC and inverter AC, i’e., when on external power, the transfer switch passes power to the roof A/C unit via the original main panel CB (factory stock!!!) – if no power is being provided from the main panel, then the transfer switch passes inverter AC to the roof A/C via a CB on the inverter sub-panel.
The “Easy Start” has been installed in the roof A/C and works REALLY well! I’m sure to find the same heat management issues as you’ve encountered, but haven’t yet decided how to best solve for heat extraction from the basement electrical utility compartment…..cross ventilation is probably in my future.
Sounds like you have it well under control.
I think perhaps the only original part of my system is the hybrid battery setup. I didn’t go with 24 volts because I didn’t want to replace my inverter.
You didn’t mention the RV you stacked all this gear on. I assume that you are going to use it very frequently.
I’m curious about several things:
1. How does one acquire the skills and confidence to undertake such a massive electronics overhaul? (I would have neither.)
2. Was the cost worth it? Or does this just represent a cool hobby and the expense becomes part of the fun? (Most hobbies cost $$$, and said cost is justified by the joy.)
3. Would any of this work on a 5th Wheel? (Remember mine?)
How does one acquire the skills and confidence to undertake such a massive electronics overhaul?
The answer is I had to hold the flashlight for my dad, under the car. After that electricity was easier to work on (and less dangerous).
I my supersized RV solar electric system worth the cost?
I could downsize everything by half and be just fine for an overnighter anywhere. Perhaps I could go nonstop in the summer.
For us, quiet and remote are worth the upfront expenditure.
It was such a joy meeting you both and couldn’t wait to get home and tell my husband all about what you do. Definitely the high point of the afternoon.
I anxiously await to see if you choose to write about our special Superstition Mountain Museum and its historical attractions.
My husband and I both will definitely be following your future travels.
I hope you had an Easter filled with many blessings.
Breeze
It was our pleasure meeting you.
Hi Scott,
The RV is a 2004 Trek 28RB. I stress-tested the system last summer with a trip to Texas following my installation of the ATS in the roof AC circuit….the ATS prioritizes the main panel source and falls back to the inverter sub-panel when main panel (external AC or Generator power) is not present. 11 hours of operating the roof AC in 110-degree ambient temps left me with a 25% state of charge at the end of the day.
This is a good comment to point out that all RVs don’t work the same way. Some inverters/converters (newer than mine) can combine the power from both a small shore power or external generator source with battery power to run an air conditioner or large load thus keeping the battery draw lower.
It is also a good time to point out again that if you don’t know how your RV works, then don’t try to change it.
Just finish a self-install solar system on the RV out of 2400 watts I am netting 1900. It’s important for people to know that you are lucky to net 75% of the rating if your panels are flat (in the summer) and 50% winter.
Chad
Yes, understanding something (in theory) is different than experiencing something. Remember also that in the summer your prime collection period is much longer than it is during the winter. I designed my array to allow a tilt and am thankful that I don’t need to do it. Perhaps I might be more willing to tilt if I stayed in one place for longer periods.
I read this article with lots of interest…. but have to say, that almost no one thinks of the hazardous situation taken into account…
The fact that running on solar, and the energy needed for the RV taken from the invertor, would be similar to a domestic installation (home).
I have a TT (Keystone), which I will equip with a solar panel system…
But to avoid the monstrous cables… I will have a system running on 24 or 48 V instead of 12V.
This has a lot of advantages, let’s say ONLY advantages…and hybrid inverter, transfer switch…
Why doesn’t no one think of this, as for every post I read, they just stick to the 12-volt.
If you want more info, don’t hesitate to get in touch with me… I’m an electronic engineer pre-retired…
I carefully considered putting in a higher voltage DC system and opted to stick with the 12-volt system for only one reason. I already had a 12-volt inverter.
I run about 68+ volts down from the roof to the controllers and the controllers would have functioned better at 24-volts to the battery (actually it would have been close to 29-volts to the battery. But again I stayed with the 12-volt main battery bank because of the inverter.
You may have noticed that if the inverter fails then I am ready to convert to a higher-voltage battery bank.
Scott, great to see your articles. Once again, Very interesting, fascinating actually. Great article. Thanks for the great info on the easy-start device. I ordered one in prep for this year’s road adventure.
We are planning a little more boondocking than in the past and like the idea of being able to run an AC unit off a smaller generator.
We have nowhere near the solar/ battery capacity you have, so will be pretty limited in our ability to run a lot of power. I can run about 4 days with my 300AH batteries and 200-watt solar charger before I run out of battery. Longer of course with the generator…
One thing I notice, you don’t talk a lot, or perhaps any about cost of your conversion to solar. Curious to know what you figure your return on investment is, though. RVs have about a 10-15 year usable life, so over that time span would the investment you’ve made in a solar conversion pay for itself in energy cost savings?
Stay safe and happy trails. My best to Tami!
Burt, good to hear from you. ROI is a moving target. Is it low-cost off-grid camping versus full hookups? But then you can do that with a generator w/o solar. For us, it is associated with being quiet and peaceful vs noise from our generator.
Scott,
I have a 2018 Newmar New Aire and I (like you) am a compulsive tinkerer. I first outfitted my rig with 900 amp-hours of Lithionics LiFePO4 batteries. Then I added 1200 watts of solar panels. Then I added a Mabru 12kbtu/hr rooftop 12 volt dc powered air conditioner over the sleeping area of the rig. Other additions include Pepwave cellular router, Starlink High Performance In-Motion Dish, water softener and reverse osmosis drinking water filter, and a variable speed freshwater pump. My coach is now a boondocking or Harvest Host special. If you are interested, I can provide reports of my installation with lots of pretty pictures.
I read your report on your efforts to get dc powered air conditioning capability in your 2008 Allegro Bus which was published on the “Camper Report” blog. It reminds me of my own experience of installing equipment and later modifying it to get better results. You and I have both learned a great deal doing these complex projects. For the most part, your report is accurate. But since many folks are reading your report, and could be confused, you might consider these minor changes.
Comments:
“My system requires a large inverter. I have friends that have direct-current (DC) air conditioners (almost experimental models) that don’t require an inverter. They can run their air conditioners longer than I can from the same battery power because this design is more efficient. My big inverter wastes about 10% of my available power and converts the wasted electricity into heat”.
DC powered rooftop air conditioners are becoming quite common, particularly on overland Class B units. They are still rare on Class A units, but some early adopters are installing them. They offer several attractive features. First, they are very efficient because they use inverter technology for their compressors. Since they are directly connected to the batteries, they overcome the coach’s inverter losses. Some units use only 50 percent of the energy that a similarly rated ac powered rooftop air conditioner uses. Thus, they can be run for up to twice the time on a given battery capacity. They also can be mounted directly over a Class A coach’s sleeping area so that by closing the sleeping area doors, only a fraction of the coach needs to be cooled at night.
“I can run one of my air conditioners for about one hour on each one hundred amp-hour lithium battery.
This might be a bit confusing to readers. A 15kbtu rooftop air conditioner might take 130 amps at 12 volts DC to run when the compressor kicks on, or 144 amps from the battery after considering inverter losses. One 100 amp hour lithium battery can continuously deliver only around 1C (100 percent of amp-hour rating) safely per manufacturers specs, or 100 amps. So, you would need a minimum of two 100 amp hour batteries to run one unit.
“I have 1800 watts solar but can only deliver 1400 watts. Solar panels are only 100 efficient in a laboratory.
Basically, this is a true statement, but there is more to the story. Solar panels are only about 22 percent efficient in converting solar energy into electrical energy. Solar panels have a temperature coefficient. In general, the lower the temperature, the more power the panel can generate. If the outside temperature was very low, and the panels were oriented into full sun, they could generate more than their rated power. However, this is highly unlikely since when it’s cold, the sun is usually at a low azimuth and RV’ers don’t usually venture out when it’s that cold. Perhaps you could say that solar panels seldom achieve their rated output except in the lab and under very rare field conditions.
“Your picture of your MPPT Installation”
Your solar controller installation looks very nice. However, I don’t see disconnects on the solar panel side of the MPPT wiring. Perhaps they are just not shown in your picture. By code, there must be a 2 pole disconnect switch on each MPPT input. Both positive and negative wires between the solar panels and the MPPT must be disconnected by the 2P switch. The black negative wire(s) from the solar panels must not be grounded anywhere, and the two MPPT negative wire inputs should not be connected together.
By the way, Victron recommends that the solar panel disconnect be opened before opening the battery disconnect when shutting down the system. Similarly, the battery disconnect should be closed before closing the solar panel disconnect when re-energizing the system. If this recommendation is not followed, damage to the MPPT solar controller might result.
“This is how my RV works — it is very likely that your RV does not work the same way!!! If you don’t understand it then don’t monkey with it”.
“Shore power or generator power enters the circuit breaker panel via the 50 amp circuit breakers (one red, one black) and energizes the red and black bus. From the red and black bus, part of the power (30 amp red and 30 amp black) is then routed to the inverter from a circuit breaker labeled “inverter out”… The power passes through the inverter and is returned to the circuit breaker sub-panel on the “inverter in” circuit breakers. (30 amp red and 30 amp black)”.
Unless you have two inverters in your rig, with their ac outputs connected in a two (split) phase connection, your inverter will be 120 volts input and 120 volts output. If your inverter is a 3,000 watt (or 2,800 watt) model, ac power to it will be fed via a 30 amp single pole breaker. There will not be a red wire. The wires will generally be black (hot), white (neutral), and bare or green (ground).
Looking at the picture of your panel, it appears that although your shore power plug may be 50 amp rated, the main circuit breaker in your rig’s panel is only 30 amps. This could be an issue if you run your rooftop air conditioner on inverter because if you overload the inverter power circuit, you might trip the 30 amp inverter breaker and the 30 amp main breaker simultaneously. If this happens, the whole coach goes dark, even if you are on generator at the time.
“This supply is broken into two branches commonly named red and black, as associated with the wire color. Both the red and black wire can each supply 50 amps to distribution. Thus when you have 50 amp service you have two sources of 50 amp power. Thus 50 amps = 100 amps of power. In my RV, and I would venture to say all RVs with 50 amp service, one air conditioner is on the red wire and the other air conditioner is on the black wire”.
Saying that 50 amps (service size) = 100 amps is a bit confusing. It would be more accurate to say that that a 50 amp service consists of two 50 amp, 120 volt legs. Saying that you have 100 amps of capacity implies that you could connect a 70 amp load, which is obviously not true.
Scott, I hope these comments are of some value to you. They are certainly meant to be constructive and not just “smart a–” jabs. Keep up the good work. Your blog is great!
Chuck Gumeson
Thanks, Chuck, great comments. All appropriate. I will transfer them to my website unless you object. Please sign up for my weekly blog updates. Most will not be nearly as geeky as this blog post.
Great article! Physics shall NOT be denied. So.. this is why RV’ers chase the 70-degree temps?
Yes! We RV’ers chase the 70-degree but we don’t always find it…