Basic RV Electrical System Guide 2022

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.

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.

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.

Therefore, when choosing an inverter, we recommend that a more reasonable configuration of the inverter will make your RV AC power supply smoother.

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.

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.