Basic RV Electrical System Guide 2022
Basic RV Electrical System Guide 2021
When traveling by RV, what RV users care most about is the power system on the RV. All kinds of AC equipment such as AC air conditioners, induction cookers, refrigerators, audio multimedia systems and even electric water heaters, require the power supply system to work stably. In addition to AC appliances, there are also DC devices that draw power directly from batteries, such as DC air conditioners, DC refrigerators, DC LED lights, and DC monitors. If you are an RV user and hope that these devices can provide stable power for your every trip, it is very important to have a basic understanding of your RV power system.
When you fall in love with RVs and use RVs frequently, understanding the power system, internal structure and logical structure will be of great reference significance for you when choosing various products. Most importantly, if there is a problem, you will know where the problem is and troubleshoot it quickly. We know that not all riders are electrical engineers, we will use the simplest language to describe.
First, let’s take a look at the professional terms in the RV power system.
DC load power (W) = battery voltage (V) * load ampere (A).
If it is a 12V system, the battery voltage is 12V
AC load power (W) = AC voltage (V) * load ampere (A).
If it is used domestically, the AC voltage is 220V or 120V
Battery capacity (WH) = battery voltage (V) * charging and discharging ampere (A) * hours (H)
We heard that many RV users directly talk about how much AH is when talking about the battery capacity. In fact, this understanding has somewhat deviated. Let’s take the lithium iron phosphate battery as an example. The surface of the battery is nominally 12.8V / 460AH, then the capacity of this battery is: 12.8V*460AH=5888WH=5.89kWh, kWh is actually the same as our electricity meter at home, which is often said to be 5.89 kWh instead of directly reading 4.6 kWh.
Now that we have talked about 12.8V, let’s deepen the understanding of lithium batteries. The nominal voltage of a single cell of lithium iron phosphate is 3.2V. When we use a 12V system, we connect four cells in series, so 12.8V is obtained. Many RV users are also very confused about the full voltage and the discharge voltage. This is very simple. The nominal value of a single battery cell is 3.2V. Generally, the maximum voltage of the built-in protection board is 3.65V, and the empty voltage can be up to 2.5V, but the basic setting is 2.8V. The conclusion is drawn: 4*3.65V = 14.6V when fully charged, and the voltage is 4*2.8V=11.2V when the battery is less than 10%.
Here a question that most concerned about are: If we feel that the battery in my RV is not enough, can I buy another set to increase the capacity? We see that many users are chaotic. For example, if they have a 400AH battery and a 600AH battery, the ideal state is to reach 1000AH, but this is not the case in actual use. When lithium batteries are connected in parallel, they will be based on the maximum capacity to calculate the cumulative value. Similar to the above parallel method, the number obtained should be 800AH, and this parallel method is not scientific and is prone to problems. So why is it so? Let’s explain. Assuming when you charge a 400AH battery, the single-cell voltage is 3.2V/400AH (multiple blocks in parallel) and a 600AH battery, the single-cell voltage is 3.2V/600AH (multiple blocks in parallel), you are charging two sets of batteries at the same time, and the capacity of the battery is related to the voltage. The built-in protection board also judges whether the battery is overvoltage. Under the same conditions, when the 400AH battery is charged to 3.65V, it starts the protection, feedbacks the battery voltage to the charger, and lets it stop charging. At this time, the 600AH battery is only charged to 400AH, it cannot reach 3.65V.
If you must use lifepo4 batteries for parallel connection, you must ask the manufacturer whether the built-in BMS can be connected in parallel? What is the maximum number of parallel connections that can be made? Similar to our BL-1280 the built-in BMS can support up to 4set parallel and series connection. In any case, please be sure to consult in detail before deciding.
Charging power (W) = voltage (V) * charging current (A). The selected AC charger or MPPT, PWM solar control charger is nominal A. For example, the battery is a 12.8V lithium iron phosphate battery; because there are two stages in the charging process (lead-acid has three stages), the first stage is called CC mode (constant current). When the battery voltage is lower than 14.6V, the charger will charge with the maximum current until when the battery voltage reaches 14.6V, it will switch to CV mode (constant voltage). At this time, the charger voltage remains unchanged at 14.6V, while the charging current naturally decreases, until the charging current drops to 10% of the rated charging current, the charging is completed. Note that unlike lead-acid batteries, lithium batteries do not require a floating charge function (FC). The floating charge will affect the number of cycles of lithium batteries.
After understanding some basic common sense, we will know that there are actually two power systems in our RV, one is a 12V DC (battery) system, which supplies some DC loads, such as DC air conditioners, DC refrigerators, and USB chargers, 12V LED lights in the RV, etc. There is also a 220VAC or 120VAC power system (through an inverter) for some large electrical appliances, such as induction cookers, microwave ovens, ovens, multimedia audio-visual systems, etc.
Know about the power consumption of the RV, you can more clearly choose the type and capacity of the battery.
Judging from the configuration of more than 100 RVs we have contacted, there are now basically very few lead-acid batteries available. Lead-acid batteries are heavy, bulky, and wear fast; while lithium iron phosphate(LiFePO4) batteries have the advantages of high safety factor, small size, and high cycle times (generally greater more than 2000 times, long life), etc., that are chosen by more and more users. The density of the ternary lithium(LiMn2O4) battery is higher than that of lithium iron phosphate, so it has the advantages of lighter weight and smaller volume than lithium iron phosphate, but also very obvious weaknesses. The safety performance is not as good as that of lithium iron phosphate, and the number of cycles is 600. The price is higher than lithium iron phosphate.
What I have to mention here is that there is a key parameter that will be ignored by all RV riders, that is the charge and discharge coefficient of lithium batteries, usually expressed as ?C. We take the 12.8V/460AH battery as an example. If the marked discharge coefficient is 1C, which means it can withstand a maximum discharge capacity of 460A. The battery can withstand 1 hour to discharge the battery, and it does not damage the battery life. If it is marked as 0.5C, it means that it can only withstand a maximum of 2 hours to discharge the battery without harming the battery; some even only have 0.2C. If the battery cell is only 0.2C, then even if your BMS or protection board can withstand charging and discharging more than this current, it will cause damage to the battery.
The same is true for charging. Lithium iron phosphate batteries on the regular market now generally have a discharge coefficient of 1C and a charge coefficient of 0.5C; that is, it can support 1 hour to discharge, and 2 hours to fully charge. This will be an important reference parameter when choosing a lithium iron phosphate battery, of course, this statement also applies to ternary lithium batteries.
After understanding the battery type, we began to simply calculate the power consumption in our RV. For example, in a 102-liter DC refrigerator A, we calculate according to the nominal display 0.39KWH/24H, the 24-hour power consumption is 0.39KWH which we commonly use. A 12V DC air conditioner B, the power of the compressor is 300-900W, we calculate it according to half the time the compressor works (if the temperature drops, the compressor will automatically stop): 900W/2*1H=0.45KWH, which means if the air conditioner used for 1 hour, it is about 0.45 kWh of electricity.
These devices are all DC devices, directly derived from the battery, and the loss is very small. In addition, there are some LED lights, which are quite small loads and can be ignored. After calculated the DC load, we calculated the AC equipment. Usually, the most used by RV users should be induction cooker C, electric kettle D, we also give an example, the maximum power of the induction cooker is 2100W, because the induction cooker is AC equipment, so its power supply is inverted from the battery through the inverter, the conversion efficiency of the inverter is very important here.
The most popular ones on the market are the low-frequency inverter with integrated charging and inversion and the normal high-frequency inverter. In the state of 12V, the conversion efficiency of the low-frequency inverter is much lower. The conversion efficiency of the normal low-frequency inverter 12V3000W is about 80%, while the quiescent current reaches 150-200W, and the conversion efficiency of the high-frequency inverter is 88%, and the quiescent current is about 300W. If you are using a low-frequency inverter, the power consumption of a 2100W induction cooker is 2100W/0.8*1h=2.6KWH. In other words, the induction cooker consumes 2.6 kWh of electricity for one hour. The power of an electric kettle is about 1200W. Usually, we can boil a pot of water in 7 minutes. 1200W/0.8*0.12= 0.18KWH, which means that 0.18 kWh of electricity is required for boiling water.
Knowing this calculation method, do you understand the power consumption in your RV? Choosing a battery with a reasonable capacity will bring enough power for your RV trip.
How to properly configure the charging method of the life battery in the RV?
There are basically three parts to charging the living battery in the RV:
1. Car motor charger
2. MPPT/PWM solar control charger
3. AC charger
There are two types of car chargers
A. Dual battery isolator: The charger that charges the “car battery” from the engine compartment at the same time charges the life battery. This kind of application is very efficient and easy to install. It charges two batteries at the same time when charging, and separates them when only the life battery is used instead of the “car battery”. According to the power of the car generator, you can choose 80-120A. If your car generator supports a charging current of 120A, then 120A*12V*1 hour=1.44KWH, which means that the life battery can be charged 1.44KWH for 1 hour of driving.
B. 12 to 12v DC charger, the advantage of this product is that it supports a wide front-end voltage input, usually 10.5-16V, similar to a dedicated charger, it can be charged in CC/CV mode. But its price will be much more expensive than dual battery isolators, and generally does not support high power.
MPPT/PWM solar controller (MPPT is maximum power point tracking, usually 20-30% higher than PWM power generation).
There is a certain space on the top of the RV to install solar panels. According to our survey, the solar panels of the general RV are 400W-800W. Here we will share the most reasonable RV solar panel power generation design. Usually, we choose even numbers when installing solar panels, because we need to involve series and parallel. If your RV is a 12V system, the best working voltage of the MPPT solar controller is 24V-36V. Of course, many MPPT controllers also say that it can work at 3V higher than the battery, but the RV is not like an off-grid solar system. The lighting and installation angle are both extremely demanding for RV, so we choose a slightly higher one. We have also checked a lot of solar panels used in RVs, which are basically around 18V, so we suggest 2 pieces in series and then parallel. If you use an 800W solar panel, it is most ideal to choose the 12V/80A MPPT solar charge controller. We have seen a lot of solar panels installed, but the actual controller did not reach, and it still can’t generate much electricity. Because of the different lighting in various places and the different parking positions of the riders, it is impossible to give an accurate answer to how much electricity the 800W solar panel can generate. However, we investigated most of the RV users who installed 800W, and they can generate about 2 kWh of electricity in 3 hours from 11:00-14:00 noon.
Here, let me share with you the experiments we have done. In fact, we have seen many RV users install a lot of solar panels on roofs of different shapes and sizes. Most users will find that 800W solar panel installed, but only has a charging capacity of more than 200W or even more than 100W. Here is my experience, because most of the single solar panels on the RV have a voltage of around 17-21V, so many users and even RV factories connect two pieces in series and then in parallel. An important theory here is that if solar panels with different power are connected in series, the current is output at the smallest piece. In layman’s terms: 150W and 100W are connected in series, the actual effect is only 200W but not 250W, so when doing the test, the actual power generation of one group of 150W+100W and the other group of 100W+100W are the same.
We saw a lot of users installed some very small pieces on RVs. If this pieces is 20W and another piece of 100W, it can only be 40W, which will be a lot of waste. Will the parallel connection of multiple groups of different powers have an impact? For example, we have one group of 150W+150W, and two groups of 100W+100W. Seeing that the power is 700W, but the actual power generation efficiency has not been reached.
The reason is that the parallel of solar panels with different powers into the MPPT will affect the maximum power tracking. Therefore, the suggestion is to install an even number of boards of the same size on the top of the RV, so that the power generation effect can be highest. Composed of a double number in the smallest unit, for example, it is recommended not to install 100W in some places and 50W in some places. just install at 50W. In our actual test, if the installation is reasonable, use the MPPT with good performance, the power generation efficiency can reach more than 50% when the sun is not particularly good, and it can reach more than 85% when the sun is big occasionally.
Therefore, when choosing to install solar panels for RVs, you must pay attention to this detail. Don’t reduce the overall power generation efficiency just because you want to increase a small piece of usable space.
Summary: When installing solar panels on the roof of your RV, choose an even number of solar panels of the same model to achieve the best condition.
AC charger for RV battery
The AC charger is connected to the mains when parking the RV to charge the battery. Commonly, there are chargers that come with the inverter. Generally, the charging current is small. If it is a low-frequency inverter, it may also be marked as 50A-80A. The charging current 12.8V of a single charger is only 100A. What does charging current mean? If there is a 12.8V/460AH battery, it takes 4.6 hours to fully charge by using a 12.8V/100A charger. The calculation formula is 460AH/100A=4.6H. It should be noted that it must use a matching charger to charge the battery. The charger parameters of different batteries are different. For lead-acid, the voltage of CC must be 15.5V. Although the lithium battery has a protective plate for protection, it is still risky and dangerous.
A summary of charging:
1. Review your general information of habits, driving time and parking time
2. A simple calculation is required for the power consumption in the RV when parking
3. If the above three charging methods are installed in the RV, get to know about the approximate distribution of the various charging methods.
After explaining the three charging methods, I believe everyone has a certain understanding of the charging methods of RVs. Next, we will talk about inverters.
The choice of the inverter is the most critical for the RV. When the RV user is parked and resting, all the large electrical appliances in the RV run on the inverter. For example, AC air conditioners (including overhead air conditioners and household air conditioners), induction cookers, kettles, televisions and so on. If there is a problem with the inverter, it all becomes a fantasy.
1. Advantages of low-frequency inverter
Three times the peak power, strong load capacity, strong shock resistance, and a high-power charger Disadvantages of low-frequency inverter Large size, heavy weight, low conversion efficiency, large no-load loss, large heat generation.
2. Disadvantages of high-frequency inverter
Double times the peak power (some manufacturers have provided triple peak power), and the load capacity is weaker than the low-frequency. Generally, there is no charger or low-power charger.
Advantages of high-frequency inverter, small size, light weight (only about 20% of low frequency inverter), high conversion efficiency (about 10% higher than low-frequency inverter), low no-load loss (only about 15% of low frequency machine), low heat generation. The long-term working shell temperature is not higher than 40 degrees (when the ambient temperature is 25 degrees).
After comparing the advantages and disadvantages, we found that the low frequency inverter is stronger than the high frequency inverter in impact resistance, and will come with a high-power charger, which makes the installation much easier.
However, it is also obvious to find that the advantages of high-frequency inverters may be more suitable for use in an RV, because the inverters are mostly installed under the seat, under the bed, or in the storage box at the rear of the car; the location of the inverter installed is small and not ventilated.
Most manufacturers are not particularly professional circuit engineers. they only think that will be fine they can put down the inverter. In fact, this enclosed space is extremely unfavorable to the inverter.
After the ambient temperature rises, it cannot be dispersed for a long time, resulting in that the components inside the inverter are aging quickly. If they are maintained at high temperature for a long time (although the inverter has over-temperature protection), the internal components are also prone to failure, causing the inverter to be damaged and unable to output.
We have seen a lot of low-frequency inverters installed by RV users, when the air conditioner is turned on, the inverter over-temperature protection does not work in the middle of the night, or the charging module is broken. Some users suggested that if you don’t need a large load, you need to turn off the inverter, because if you don’t turn on the load, the low frequency inverter has a loss of 100-200W, and it consumes 0.1-0.2KWH electricity in one hour. This has created a very difficult decision for many users.
Therefore, when choosing an inverter, we recommend that a more reasonable configuration of the inverter will make your RV AC power supply smoother.
Which plan is more suitable for you? Let’s recommend a set of configurations (12V/3000W system):
1. 3000W high frequency sine wave inverter with bypass function.
Advantages: When the main supply is connected, the electricity in the RV will be directly transferred to the mains supply, the inverter will no longer work, and there will be no self-loss and heat generation. Usually not connected to the mains, the high-frequency sine wave inverter has the advantages of high conversion efficiency, low self-loss, and low heat generation. The actual 6000W peak power of 3000W inverter can start most of the large electrical appliances in the RV, overhead air conditioners, household air conditioners, kettles, audio-visual systems, etc.
2. MPPT solar controller 12V/24V/48V adaptive 60A.
Advantages: Why choose 12V/24V/48V adaptively? The reason is that in case you change the 48V system on a whim, you can still use it. The 48V/60A MPPT solar controller can support up to 876W (14.6V*60A) solar panels, but in fact, even if we install 800W solar panels on the RV, under normal circumstances, it cannot reach such a large power. But if your configuration is too small, you will not be able to achieve the maximum effect. The 60A MPPT solar controller can meet most of the DC load, even if the weather is not so good, the electricity generated is enough for the DC refrigerator.
3. 12.8V LiFePO4 dedicated mains charger 100A.
Advantages: When connected to the mains, quickly charge the life battery in the RV. We mentioned this charge and discharge coefficient when we talked about the battery above. If the lithium battery is 200AH and the charge factor is greater than 0.5C, it only takes 2 hours to fully charge the battery when it is connected to the mains. The advantage of the independent AC charger is that it has its own fan and over-temperature protection function, which is more stable and safer in the state of mains charging.
4. 12V to 12V dual battery isolator 120A.
Advantages: I personally think that this will be the best and fastest charging method. If our car generator has a charging current of 100A, when this dual battery isolator is installed, it can charge 1.2kWh every 1 hour when driving. For RV users, it is the most comfortable state to drive for 3 hours per trip and rest for one night at the station. If equipped with dual battery isolators, it can fully meet the electricity needs of one night. So please don’t ignore this key configuration.
It depends on the design of the electrical system in your RV, especially the selection and design of the AC charging and inverter determine if that operation is needed.
RV owners need to use the AC equipment in the car when they stay in the car, especially in summer, the temperature inside is very high and it needs to turn on the air conditioner for a long time, but many owners have refrigerators running 24 hours; this time the battery will not be enough, the power of the solar system in the RV is limited, or there is not always good sunshine to support the power generation, then it will be necessary to plug in the mains in the premises or basic to charge the battery and powering the load at the same time. In this case, should I disconnect my RV battery when plugged in? we need to talk about two cases, which have the difference between inverters with bypass function and DC to AC inverters.
1. With bypass inverter
If your inverter has bypass function, there is no need to do anything when plugged in to the grid. When the grid is detected, the inverter with bypass function will automatically switch to grid to provide the power for the load in the car, the BP series with bypass inverter has a switching time <19ms. We highly recommend using our BP series with bypass inverter + Ares series battery charger, when the bypass inverter switch to grid, also the Ares series battery charger will charge the battery, it is a very smart solution for RV power charging and electricity system. And the Ares series battery charger provides a maximum charge current of 12.8v 100amps, even if you have a 12.8v/1000ah battery, it only takes 10 hours to be fully charged, which is a very good choice.
Inverter with bypass function generally has two modes, a. Grid priority b. Battery priority . Choose the corresponding mode according to your situation. If you are using inverter charger, some models will also have bypass mode, such as our BP with charger series, but we also found some cheap inverter charger in the market, just DC to AC inverter + ac charger does not have bypass mode, please pay attention to the choice.
2.DC to AC inverter
Many caravan manufacturers or conversion plants, in order to reduce costs, in the caravan only installed DC to AC inverter, it is completely separate from the grid, and will be installed a converter at the same time. If grid plugged in before the inverter is off, and then the converter to the mains. Operate correctly, otherwise the gird plugged in will burn the inverter, but there is no relationship with the battery, it will not damage the battery .
Many RV owners design their RV electrical system based on information from the internet, but in reality you need to know about the equipment inside your RV and design your electrical system based on the equipment. We know that there is DC and AC power in an RV, and that the two types of power will be provided to different equipment to run. So what we need to know is which equipment in your RV is running on a 12 Volt DC system to determine how many power an inverter need to be used to power AC equipment, we here list some of the equipment that can operate in 12 Volt and is readily available in the market for RV use.
1. DC air conditioner (900W)
2. DC LED lights (20W)
3. DC monitoring system (10W)
4. RV electric bracket (150W)
5. Ventilation fan with LED light (23W)
6. USB charging socket (15W)
7. Range hood for RV (60W)
8. DC refrigerator 105L (50W)
If your RV is equipped with the above DC products, then you can simply figure out the other devices that use 110V or 230V AC. Usually now 12VDC 3000W high frequency pure sine wave inverter bypass is popular, it is different from the low frequency pure sine wave inverter, which has the advantages of light weight, high efficiency, low heat generation, static current, etc.. We all know that weight and heat generation is very important for the RV, compared with high frequency pure sine wave inverter, the installation of low frequency inverter is equivalent to the weight of an extra person on your car, of course, the weight of a child, which is almost 25kg. The quiescent current will consume the power of RV battery quickly, which will become very critical in the RV that lacks power itself.
As long as your power supply system and refrigerator can work normally, the cooling of the refrigerator will not be affected whether you are driving or parking. We have also done a lot of investigations and have helped RV refitting to complete the transformation of many RV power systems. Many customers are worried about their refrigerators, in the life of RVs, refrigerators seem to be more important than air conditioning.
Many RV owners drive RV to travel long distances, so they need to store some food in the refrigerator which is not available everywhere. If there is any problem with the refrigerator, the food will go bad. So, the concerns are justified. We found many RV owners have installed 200W-400W solar panel on the roof of the car, using DC air conditioners, but still cannot meet the running of the air conditioner, and the power of the refrigerator is 100W. Why? We inspected a lot of RVs and found that the installation of the solar panels didn’t meet the specifications. In order to install more solar panels on the roof of RV, which usually leads many different size of solar panels to be composed on the RV roof. It will not increase but reduce power generation. If it is connected in series, it will generate electricity with the minimum power current. That is to say, if you connect 50 strings in series with 100W, the actual power obtained is only 100W, and the other 50W will not work. Because of this, many refitting factories think taht we must connect all the solar panels in parallel, such as 100W+50W+30W, of course, it may solve some problems, but this will be unfriendly to the solar controllers, and even the connection cables will be difficult. Beacuse multiple cables connected, if professional tools not be used, there is a risk of unrellibale connection. If you don’t use an MPPT solar charge controller, it will not work better and unable to track the maximum power point, this will also lose a certain amount of energy.
We recommend all the RV owners to install solar panels of the same size as much as possible. If they are used in series to increase the PV input voltage and use MPPT soalr charge controller, more energy will generated.Installing reasonable solar panels will not affect your refrigerator whether you are driving or parking. As long as there is reliable electricity, your RV refrigerator will always work for you, bringing you fresh food and cold beer.
we saw David & Ninette’s video again. This is a blogger from YouTube. They are full time RV enthusiasts. Please note that they don’t play RVs occasionally, but live in RVs for a long time. David said this has already been 4 years. We can follow David’s YouTube channel: Tigner Adventures. David will tell you a lot about RV solutions, which is very important because he has verified.
We noticed that this issue of his video is mainly about the solar system of the RV. Someone left a message “this is one of the best videos on solar that I have watched”, so we must share thei video to everyone. We notice that AGM battery, battery shunt, AC charger, MPPT solar charge controller, solar pannel and BP series 3000W pure sine wave inverter are used in the video. We are very happy the CNBOU’s inverter has accompanied David and Ninette for four years. It is our honor that our products work normally within four years to provide all AC power for their lives.
David talked about how his RV power works, and make you know how much solar panel you need depends on how many Ah your battery system is and how many hours you need to fully charged. Of course he also talked about how much load this solar system can work, such as TV sets, microwave ovens, computers and so on. This is a very real case, worthy of your reference.
Thanks again to David, Please click on the source video address: do you need solar and do you understand the process.