How big of a battery does an RV need

October 29, 2022 US Team

China, the opposite of European and American people’s RV usage habits, is almost “light gas and heavy electricity” in RV life. In contrast, European and American countries are “heavy gas and light electricity.” This result orientation is that our domestic RV users always feel There is insufficient electricity in the RV, so what should I do? The solution is to buy an RV with a complete gas system; another solution is to increase the RV battery capacity and improve the circuit system. So, how much battery capacity does an RV need to be enough? It must be what many RV novices want to know. Let’s learn about the circuit system on the RV through a senior RV user-Yang, Calle. This theoretical basis is obtained after a detailed calculation of user needs.

Power Systems

The power system on the RV is nothing more than these types: external mains, generator, solar powered generator. Advantages of external mains: no noise, basically unlimited power consumption; Disadvantages: it isn’t easy to find a place to connect to electricity when you go out. The advantages of generators are unlimited electricity use at any time and having oil; the disadvantages are loud noise. Advantages of solar power generation: no noise and the sun can generate electricity; disadvantages: low power generation efficiency, only enough electricity for lighting or refrigerators.

Electricity storage system

There are two types of power storage systems: lead-acid batteries and lithium batteries. Advantages of lead-acid batteries: safe and cheap; disadvantages: small storage capacity, large weight, no deep discharge, and relatively short life. Advantages of lithium batteries: large storage capacity, lightweight, deep discharge, and relatively long life; disadvantages: safety is worthy of attention, and the price is high.

Transmission and consumption system

The power transmission system mainly comprises wires, cables, copper bars, etc. The wire diameter needs to be calculated according to the power consumption demand.

The electricity system includes 12V electricity and 220V electricity. The lighting and refrigerator in the RV are generally powered by 12V, and for the TV and air conditioner, it is recommended that you purchase 12 volt batteries. Socket and other common household appliances are all powered by 220V.

Electrical Requirement Estimation

Everyone should know that energy is conserved, and the total demand of our power system plus the loss of the power transmission system cannot be greater than the maximum amount that the power system can provide. Therefore, we infer what kind of power supply or storage system is needed according to the electricity demand. Moreover, it can be deduced what kind of wire diameter is safe according to the electricity demand. In the following, we take the calculation of battery capacity as an example, mainly used for electric literacy estimation; please ignore it for professionals.

Use simple junior high school physics knowledge to help us estimate electrical requirements, P (power) = U (voltage) × I (current), for example: 1W = 1V × 1A. Watt (W) – a unit of power commonly used in kilowatts (kW), that is, 1000W. Kilowatt-hour (kW h) – 1kW h = 1 kWh (1 hour of work done with 1kW power), volt (V) – voltage unit, ampere (A) – current unit.

First of all, find out the power of your electrical appliance. The exact value can be obtained from the sign on the back of the electrical appliance.

Electric power estimation for common RVs:

Air conditioning heating is generally about 2500W (electric auxiliary heating).
Air conditioning refrigeration is generally about 800W.
The induction cooker is generally about 2500W.
The electric kettle is generally about 1500W.

Note: High-power electrical appliances are not recommended for RVs. The power of a single electrical appliance is preferably below 3000W, and high-power electrical appliances should not be used simultaneously. The maximum power determines this that the generator or inverter we can carry can provide. What does an inverter do?

Let’s take the air conditioner that everyone cares about most and has the highest power as an example. If you want to turn on the air conditioner for 10 hours in summer, the required energy is 800W×10h=8kW·h (8 kWh), based on the formula: power×use time= Power consumption.

The above calculation is a theoretical value, and other electrical appliances can be analogized similarly. The total energy consumption of all electrical appliances is summed up to obtain the total electricity demand. The power consumption demand should be estimated at a larger value to ensure sufficient power supply for the reverse push.

Through the above estimates, you can calculate the electricity of your electrical appliances and add them together to obtain the total demand according to your personal needs.

Example:

Watching TV for 5 hours≈280W×5h=1400Wh=1.4kW·h=1.4kWh; using a rice cooker for half an hour≈800W×0.5h=0.4kWh; using the air conditioner for 10 hours≈800W×10h=8kWh; total electricity consumption Demand: 1.4+0.4+8=9.8 kWh.

Choose batteries according to your needs

The above example shows that our electricity demand is 9.8 kWh. According to the demand, we can see that the 12v lithium battery of at least 1000Ah or more will meet our user’s demand. Of course, this is only a theoretical calculation. We have ignored many low-power electrical appliances, such as lighting, refrigerators, mobile phone charging, notebook computers, etc., and we have not considered the losses in the power transmission and inversion process. The real calculation is much more complicated than our example. We will not discuss it here. It is only for electric novice self-estimation. When choosing a battery, we also need to comprehensively consider practical factors such as safety, price, lifespan, ambient temperature, weight (affecting the weight of the RV), etc., which will not be expanded here.

Transmission system

Here we mainly introduce the selection of various wire and cable air switches. The most unstable factor in the circuit is the current. Excessive current will cause heat, which will cause a fire. The wire diameter is thin, the safe current carried is small, and it is easy to heat. The joints are connected virtually, easily heat up, and short-circuited wires and extremely large heat. Therefore, the most important thing in the power transmission system is calculating the current and selecting the corresponding thickness of wires or cables and air switches according to the calculated current.

Current calculation

For example: using 220V to supply a 3000W air conditioner, I=P/U means current=power/voltage, 3000W/220V≈13.64A. Note: 12V DC power supply and 220V AC power supply can be calculated according to this calculation. Check the national standard to know the safe current carrying capacity of copper core cables.

Choice of wires

We all know that 1.5 square wires are often used for lighting, 2.5 square wires for sockets, and 4 square or 6 square wires for air conditioners because the thicker the wire, the greater the safe current carrying and the less heat. Some RV manufacturers tend to have thin wiring and rough joints to save costs. There may be no major problems in short-term use, but long-term use may not be safe.

My example here is a simple theoretical calculation; without considering the simultaneous coefficient and power factor, it is only for the reference of electric novice estimation. Professionals, please ignore this. In short, we choose the corresponding wiring and air switch according to the calculated current. Remember, the thicker the wire, the safer it is. Of course, the wire joint technology must be in place. Virtual connections and short circuits are likely to cause excessive currents and cause fires.

Inverter selection

It would help if you chose an inverter according to your power consumption. If you need a battery to drive an air conditioner or an induction cooker, choose an inverter with at least a 3000W power inverter or more. If you only need to use a rice cooker or electric kettle, an inverter with at least 2000W or more. Some manufacturers have original 300W inverters. I can only laugh. The inverter must choose a pure sine wave, do not choose a correction wave. The wire from the battery to the inverter must be thick (you can calculate it yourself), the space is limited, and the inverter will not be discussed.