How to choose suitable RV lithium battery?

How much capacity of battery does a RV needed? Many RV owners must be curious to know that. Bonnen Battery lead you to understand. Bonnen Battery has calculated the circuit system and user requirements on the RV in detail in a rough theoretical basis.

RV Power Consumption Diagram

Power Supply System

The power system on the RV mainly include these type: external power, generator, and solar power. Advantages of external mains: no noise, no restrictions on electricity consumption; Disadvantages: It is not easy to find a place to receive electricity when going out. Generator advantages: electricity available at any time as long as there is oil; disadvantages: louder. Advantages of solar power generation: no noise, solar power generation; disadvantages: low power generation efficiency, only enough for lighting or refrigerator power.

There are two types of storage systems: lead-acid batteries and lithium batteries. Advantages of lead-acid battery: safe and cheap; disadvantages: small storage capacity, heavy weight, inability to discharge deeply, and short life. Lithium battery advantages: safe, large storage capacity, light weight, deep discharge, long life; disadvantages: the price is higher than lead-acid batteries. However, because the life of a lithium battery is usually 5-6 times longer than that of a lead-acid battery, the total cost of a lithium battery will not be higher than that of a lead-acid battery in the long run. Therefore, Bonnen Battery strongly recommends that senior players choose lithium batteries as the energy storage for the RV. For example, Bonnen Battery 12V 100AH/200AH.

12V100AH RV lithium battery

Transmission and power system

The transmission system is mainly composed of various wires and cables or copper bars, and the wire diameter needs to be calculated according to the power consumption requirement.

The power consumption system includes 12V power and 220V-240V or 110V power. The lighting and refrigerator in the RV will generally be powered by 12V. The TV, air conditioner, socket and other commonly used household appliances are powered by 220V-240V or 110V.

Electrical demand estimate

Everyone needs to know that energy is conserved, and the total demand of our electricity system plus the loss of the transmission system cannot be greater than the maximum limit that the power system can provide. Therefore, we can use what kind of power supply or storage system is needed according to the demand of electricity. Moreover, it is safe to reverse what kind of wire diameter is required according to the demand for electricity. Below we take the example of the RV lithium battery capacity of the Bonnen Battery, which is mainly used for the estimation of electric white literacy. Please ignore it for professionals.

Using simple physics knowledge to help us estimate the electrical demand, P (power) = U (voltage) × I (current), for example: 1W = 1V × 1A. Watt (W) – power unit, usually kilowatts (kW) or 1000W. Kilowatt hours (kW•h) – 1kW•h=1 kWh (1 hour of work at 1 kW), volts (V) – voltage unit, ampere (A) – current unit.

First of all, you must figure out the power of your appliance. The exact value can be obtained by using the signboard behind the appliance, as shown below:

Common RV electric appliance power evaluation: air conditioning heating is generally about 2500W (electric auxiliary heating); air conditioning refrigeration is generally about 800W; induction cooker is generally about 2500W; electric kettle is generally about 1500W. Note: It is not recommended to use high-power appliances for RV. The power of a single appliance is preferably below 3000W. High-power appliances should not be used at the same time. This is determined by the maximum power that the generator or inverter that we can carry can provide.

For example, if you want to open the air conditioner for 10 hours in summer, you need energy: 800W×10h=8kW•h (8 degrees). The formula is: power × use time = Consume power.

The above calculation is the theoretical value, and other electrical appliances can be analogized analogically, and the total energy consumption of all electrical appliances is added as the total electricity demand. Power consumption requirements should be estimated at a large value to ensure that the reverse power supply is sufficient.

With the above estimates, you can calculate the total amount of electricity used by your individual appliances based on your individual needs and superimpose them to aggregate demand. Example:

Watch TV for 5 hours ≈ 280W × 5h = 1400Wh = 1.4kW • h = 1.4 kWh; use rice cooker for half an hour ≈ 800W × 0.5h = 0.4 kWh; use air conditioner for 10 hours ≈ 800W × 10h = 8 kWh; Demand: 1.4 + 0.4 + 8 = 9.8 kWh.

Energy estimate provided by the lithium battery for RV

Calculation method (take 100Ah as an example, that is, discharge with 100A current for 1 hour), (12.8V×100A×1h)/1000=1.28kW, according to the formula: (voltage × current × discharge time) / 1000 = supply of electricity.

Note: The above is pure theoretical calculation, Lithium battery is not recommended to use up all the power; lithium battery is recommended to discharge with 80% DOD depth, 1.28 × 0.8 = 1.024 kWh.

In summary, the common lithium battery is taken as an example: 240Ah ≈ 2.304 kWh; 500Ah ≈ 4.8 kWh; 600Ah ≈ 5.76 kWh; 800Ah ≈ 7.68 kW; 1000Ah ≈ 9.6 kWh.

Select RV lithium battery according to demand

Through the above examples, we know that our electricity demand is 9.8 kWh. According to the demand, we can see that the lithium battery of at least 1000Ah will reach our demand. Of course, this is only a theoretical calculation. We have neglected many low-power appliances, such as lighting, refrigerators, mobile phone charging, laptops, etc.; and did not consider the loss during transmission and inverter. The real calculations are much more complicated than our example. We won’t discuss it. It’s only for electrical new player self-estimation. When actually selecting the battery, we must consider the actual factors such as safety, price, life, use environment temperature, weight (affecting the weight of the RV), etc., and do not expand here.

Transmission system

Here, we mainly introduce the choice of various wires and cables. The most unstable factor in the circuit is the current. If the current is too high, it will cause heat, which will cause fire. The wire diameter is small, the safe current is small, and it is easy to generate heat. The joint is imaginary, easy to heat, short-circuited with wires, and extremely hot. Therefore, the most important thing in the transmission system is to calculate the current, and select the corresponding thickness of the wire or cable according to the calculated current and open.

Current calculation

For example: use a 220V power supply 3000W air conditioner, I = P / U is current = power / voltage, 3000W / 220V ≈ 13.64A. Note: 12V DC power supply, 220V AC power supply can be checked according to the national standard to know the safe current carrying capacity of copper core cable.

Although we can see that the 1.5 square wire can already be carried, considering the service life and heat generation of the wire, we can enlarge the choice and give the safety margin.

Wire selection

As we all know, home decoration often uses 1.5 square wires for lighting, 2.5 square wires for sockets, and 4 square or 6 square wires for air conditioners, because the thicker the wires, the larger the safe current carrying capacity and the smaller the heat. In order to save costs, some RV manufacturers tend to have thin wiring and rough joints. There may be no major problems in short-term use, but if used for a long time, there may be potential safety hazards.

I am here to give a simple theoretical calculation, without considering the simultaneous coefficient and power factor, only for reference. Professionals please ignore. In short, we select the corresponding wiring and air-open according to the calculation current. We remember that the thicker and safer the wire is, the more the wire joint process must be done. The virtual connection and the short circuit are likely to cause excessive current and cause fire.

Inverter selection

You need to select the inverter according to your power consumption. If you need a battery to drive the air conditioner or induction cooker, choose at least 3000W inverter. If you only need to use a rice cooker or electric kettle, the inverter is at least 2000W. Inverter must choose pure sine wave, do not choose correction wave. The wire that the lithium battery leads to the inverter must be thick (specifically, it can be calculated by itself), the space is limited, and the inverter is no longer discussed.

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