RV Battery ( Enegry) : Selection, Assembly, Protection

As the energy storage centre of the RV, the life of the battery is one of the most important accessories in the RV ( RV Battery ). As a front-line brick mover in a power plant and an RV enthusiast, I will share some basic RV battery knowledge to facilitate players buying RVs. Many opinions are only from one family. Comments are welcome, and exchanges and discussions are welcome.

  A. RV Battery Selection, Assembly, Protection  

  1. There are many types of batteries. Which battery is better for RV?  

✔ Lead-acid batteries, gel batteries, wound batteries, polymer batteries, lithium manganate, lithium titanate, ternary lithium, lithium iron phosphate, graphene batteries, lithium-sulfur batteries, solid-state batteries, and many more.

✔At this stage, RV players have heard that more lead-acid and lithium-iron phosphate batteries are used. As for the future, which kind of battery can be commercialized and applied on a large scale, no one can say for sure. It will require continuous research and development by scientific and technological personnel.

✔ Gel batteries are also a type of lead-acid battery. Using lead-acid batteries with high-power electrical appliances such as air conditioners, lead-acid batteries are scrapped in three or four months. I have not personally tested the opinions given by senior riders. This is also easy to understand.

The lead-acid battery is not a power battery and does not support high-power discharge. At this stage, RV manufacturers come standard with lead-acid life batteries, and many riders replace them with 12v lithium batteries as soon as they pick up the car, which causes a certain amount of waste.

✔ Lead-acid batteries have a history of more than 100 years and are safe, but they cannot keep up with the development of the times. Lithium is only relatively safe. All kinds of batteries have their applications.

✔ RV players still choose the one that suits them according to their purpose. At this stage, iron and lithium are still used in RVs. Only a few players use ternary lithium batteries to move the battery and protection module assembly of new energy cars to the RV.

  2. Are RV lithium iron phosphate batteries safe or not?  

✔ In real life, everyone’s mobile phone is a 5V lithium battery, a power bank is a lithium battery, a notebook is a 19V lithium battery, an electric vehicle has a 48V battery, a base station battery also has a 48V lithium battery, and new energy cars and buses have 400V lithium batteries. , and even more ternary lithium new energy cars than lithium iron phosphate cars.

✔ It is mentioned here that whether 12V, 48V, or 400V lithium batteries are composed of single cells, 48V base station batteries and 400V new energy car batteries with industry standards and specifications are even safer than 12V small workshop batteries, which can be disassembled.

✔ Comparing the 12V battery pack produced by the workshop with the 400V battery pack of the new energy car, the battery connection piece and the protection monitoring module are not at the same level. It is more than a gap between heaven and earth. Don’t believe that a few skirmishers can be safer than the batteries assembled by the regular army.

However, the regular army does not look down on the small market of RVs, so regardless of the voltage level, RV lithium batteries are relatively usable, and even ternary lithium batteries for RVs can be used. Only The importance of assembling and protecting the monitoring module of the RV lithium battery is emphasized here.

✔ There is no absolute safety. Lithium iron phosphate is only relatively safe. Let me tell you about my personal experience. In Shandong, it has been tested at a minimum of minus 15 and a maximum of 42 degrees. It is normal; after the battery is soaked in water, there is no fire accident. Specific tests such as acupuncture, collision, and high temperature are unknown to individuals.

  3. Why do big RV manufacturers not use lithium batteries?  

✔ Because only RVs can be charged while driving, and buses and pure electric cars do not need to be considered. Lithium battery charging requires a constant current and voltage method, which motorhome generators cannot achieve.

✔ Complete lithium battery charging scheme: 1. Stable DC voltage > 2, monitoring feedback circuit > 3, protection board > 4, lithium battery. 1 and 2 are in the charger, 3 and 4 are in the lithium battery pack, the lead-acid battery does not need 1 and 2, and the lithium battery of the RV life battery needs, the RV driving charge cannot meet the first two points.

✔ The popular point is: lead-acid charging eats coarse grains, while lithium battery charging eats fine grains.

✔ Audi A8L adopts a 48V mild hybrid system for hybrid vehicles, which solves the problem of driving lithium battery charging.

However, a set of three-in-one rectifier charging protection modules is more than 90,000 yuan, and the Geely Great Wall set is also 50,000 yuan, which cannot be transferred to consumers.

Regarding this point, it is a message from a player to me, and some readers have given objections, but I hope to explain the reasons and solutions.

✔ The possible reasons why large RV factories do not use lithium batteries are: first, they are worried that the lithium batteries are not safe. They are responsible for the players while ensuring the rigour of the big manufacturers. The second is to let the players install the lithium battery and transfer the after-sale service. The fourth is that the big factory installs the lithium battery.

It is necessary to sign a waiver agreement, that is, to pay the fee twice for the purchase of the car and for the modification, that is, to pay for the car twice, to avoid tax evasion; It is a marketing routine. Lithium-ion battery options rely on low prices to attract popularity first.

  4. Are Lithium Batteries Expensive?  

✔ I think it is expensive.

First, players like RVs but are poor, so they think it is expensive. Second, there is no industry standard, information is asymmetric, and the prices of old and new batteries are not transparent. There is a huge gap in one kilowatt-hour of electricity; third, there is a lack of basic theoretical knowledge, especially for some elderly RV players, who can only buy batteries assembled by others; fourth, the actual hands-on ability is even worse, no welder, no assembly, and labour costs are very expensive.

✔ Some RV players assemble by themselves, and the 1000AH lithium battery is about 10,000 yuan. If you pay attention to the battery network, with the advancement of battery cell technology such as BYD and CATL, the energy density of the battery is further improved, and the price is further reduced.

✔ It is also mentioned here that the price of photovoltaic panels has also decreased significantly.

The hardboard is almost two or three yuan per watt, and the photovoltaic panels of the RV should not stay in the era of more than 40 yuan per watt more than ten years ago.

  5. What are some basic parameters of lithium batteries?  

✔ No matter how big the lithium battery is, it is composed of small cells in series and parallel. The voltage of the lead-acid battery is 2V, the lithium iron phosphate is 3.2V, and the ternary lithium is 3.7V. The quality of the battery mainly depends on the battery voltage and each cell’s capacity.

✔ Whether the internal resistance of the cell is the same, that is to say, the matching of the capacity and the consistency of the internal resistance of the battery.

✔ RV players who buy batteries can also look at the capacity distribution equipment of the battery assembly factory and ask about the internal resistance capacity to determine whether the assembly is reliable. Of course, many small assembly factories do not have capacity distribution or internal resistance measurement.

✔ In addition to the voltage and capacity of concern, there is also an energy density, weight, and charge and discharge rate C. Use the size of C to determine whether it is a powerful battery and whether it can be quickly charged and discharged.

The higher the energy density, the better, and the higher the charge and discharge rate C, the better, but at the same time, the price is also higher.

The energy density of 300WH/kg means that 10kg stores 3 kWh of electricity. 500AH, 0.2C charging, 2C discharging means that the maximum current can be charged at 500*0.2=100A, and the maximum can be discharged at 500*2=1000A.

  6. Why can the second-hand, third-hand lithium battery on the bus also be used in the RV?  

✔ From the above lithium battery parameters, we can know that power batteries power the buses. The charge and discharge rate C is very large, both of which are 10C and 20C discharge rates (it is said that the aircraft model has reached a rate of 70 to 80 C), the number of C If it is large, it can discharge with a large current, while the previous comparison of the RV is a small current discharge.

✔ It can be understood in this way that the bus is a battery that drives a car of people and a car body weighing several tons. It needs to discharge a lot of C, and the small 6000-watt inverter on the RV is not worth mentioning. C is very small. This also means that second-hand batteries can no longer be used in buses, but using them in RVs for a few years is no problem. Or to understand it this way, the lead-acid electric car at home can no longer be used after three years, but it is no problem to use small light bulbs for lighting.

✔ Let me also say here that it is not as good as increasing the capacity of the RV by increasing the lithium battery rate. Because the RV’s power consumption determines the RV’s power consumption, even if you are equipped with a battery with a 10C discharge rate, it is generally not even 0.5C. The reason why the power of the RV inverter is too small, even that the RV is equipped with a 6000-watt inverter. What kind of high-rate lithium RV battery (12v or 24v battery) is advertised, which can be quickly charged and discharged and is of little use?

✔ Therefore, many RV players go to buy second-hand and third-hand bus batteries to assemble RV lithium batteries by themselves. Many so-called first-hand batteries on the Internet are just flickers.

✔ Jack Ma’s purchase platform, many battery manufacturers, lithium iron phosphate batteries, 3.2V 20AH, 50AH, 120AH, 240AH, 500AH, etc. There are many monomers, seven or eight hundred yuan per unit of electricity exists in large quantities, second-hand and third-hand three or four hundred Yuandu electricity, with the development of technology, the price will be lower.

  7. Those manufacturers of lithium batteries?  

✔ Many battery cell manufacturers, BYD, CATL, Guoxuan Hi-Tech, AVIC Lithium, Wanxiang Qianchao, Lishen, etc. Generally, RV players only know BYD, CATL of CATL does not know much about the batteries of various manufacturers. It’s okay in the car.

✔ Base station batteries: There are many 4850 base station batteries, such as Shuangdeng, Nandu, Yiwei, Penang, Haisida, etc. Some RV players choose this because most of them are stolen in the computer room, so they are cheap. Because the base station battery lacks the management control monitoring system, the safety is less, and the RV players do not use it much.

✔ The performance and safety requirements of lithium batteries for RVs, as well as the harsh conditions of use, are less than 1/10,000 of those of buses. You can choose the brand of iron-lithium batteries.

✔ It is best to choose the one with a higher energy density. There are also very few players who choose three. Yuan Li, of course, has a higher energy density, but the safety is reduced. If the ternary lithium does not install the battery management monitoring system of the new energy car, it is not recommended to use it.

  8. It is very cheap to assemble the lithium battery for the RV alone, but it is impossible to assemble. Is there a large unit with high voltage?  

✔ The lead-acid battery cell voltage is 2V, the lithium iron phosphate cell voltage is 3.2V, and the ternary lithium cell voltage is 3.7V. It is a world problem to improve the cell voltage of the battery. This is caused by the chemical properties of the positive and negative electrode materials of the battery and the density of the electrolyte. It was decided that the laboratory’s highest single battery voltage today is only five or six volts.

✔ The 48V electric vehicle lead-acid battery in daily life consists of four 12V lead-acid batteries in series. When you open the battery compartment of the electric vehicle or replace the battery, you will find 4 pieces. This small piece of 12V comprises 6 2V monomers in series, and the monomer is a 2V lead-acid battery instead of a 12V piece.

✔ Any 48V battery on the market (including 12V and 220V batteries) is composed of small cells with a voltage of 2.0 or 3.2, or 3.7 in series and parallel. There is no 48V cell, but the cell’s capacity can greatly improve. Lithium iron phosphate 3.2 V 400AH, 500AH, and even 1000AH monomers are available. You can purchase and assemble them according to the needs of your RV.