RV solar panels and RV lithium iron phosphate battery

Nowadays, solar-powered RVs are becoming more and more popular. Most RV customers install solar panels on the roof of their RV.

When searching for small solar power system, there will be different solar panels with different prices. Some even look the same, but the prices are quite different. So how to choose reliable solar panels among them?

Solar modules are divided into monocrystalline, polycrystalline, and amorphous silicon. Nowadays, most solar panels are mainly monocrystalline and polycrystalline materials. The photoelectric conversion efficiency of the three materials is monocrystalline silicon (up to 17%) > polycrystalline silicon (12-15%) > amorphous silicon (about 5%). But crystalline silicon (monocrystalline silicon and polycrystalline silicon) in low light has no power generation, and amorphous silicon low light types are good (in low light, the energy would have been very small). In summary, using monocrystalline silicon or polycrystalline silicon solar cell materials is appropriate.

Monocrystalline solar panels & polycrystalline solar panels

Before purchasing camping solar panels, we must first confirm whether we are going for monocrystalline or polycrystalline panels.

Monocrystalline silicon solar cells’ current photoelectric conversion efficiency is about 15%, with the highest efficiency reaching 24%, the highest of all types of solar cells. Still, the production cost is so high that it is not yet widely and universally used. Because monocrystalline silicon is typically encapsulated with tempered glass and waterproof resins, it is robust and has a lifespan of 15 years and up to 25 years. Therefore, monocrystalline panels are currently the mainstream of the market.

The manufacturing process of polycrystalline silicon solar cells is similar to that of monocrystalline silicon solar cells. Still, the photoelectric conversion efficiency of polycrystalline silicon solar cells is much lower, with a photoelectric conversion efficiency of about 12%. In terms of production costs, they are cheaper than monocrystalline silicon solar cells, and the materials are easy to manufacture, which reduces power consumption. The overall production costs are lower, so they are highly developed. In addition, the lifespan of polycrystalline silicon solar cells is shorter than that of monocrystalline silicon solar cells. Monocrystalline silicon solar cells are also slightly better in terms of performance-to-price ratio.

So, to make better use of solar energy and play the role of solar panels, it is recommended to opt for monocrystalline solar panels.

Selection of the solar module output

The maximum power of solar panels Pmax = open circuit voltage × short circuit current, which represents their ideal power, and the power rating of solar cells is usually measured in Pm. In practice, the rated power is less than the maximum power, mainly because the output efficiency u of the solar panel is only about 70%. Due to the intensity of the received light, the power is also different at different times. According to the experimental data, its average power is P = 0.7Pm. If the solar panel is to drive the load directly and the load is to work stably for a long time, the rated power of the load is Pr=0.7Pm. If the power of the solar panel is selected according to the power of the load, the power of the battery is Pm = 1.43Pr. That is, the solar panel’s power should be 1.43 times the load power.

When choosing the performance of solar panels, the power consumption of the load should be chosen appropriately so that the power generation and power consumption are balanced. Of course, solar panel power generation is also limited by many factors, such as seasons, climate, geographic environment, and spare time.

Steps to choose the solar panel

  1. Weight, the lighter, the better. Since the weight of the RV itself, various appliances, and necessities already take up a lot of weight, it is recommended that solar panels be lighter while maintaining efficiency.
  2. The relationship between temperature and efficiency. When ordinary glass is used as the surface encapsulating material, the light-transmitting and heat-conducting properties of the glass will increase the temperature of the solar cells, which will gradually affect the power generated by the solar panels as the temperature rises. (When the temperature exceeds 25℃, the solar panel’s performance will decrease by 0.3% for every 1℃ increase in temperature.) Using ETFE surface encapsulation material, air circulation is created between the solar panel and the roof space. Reducing the temperature reduces temperature and ensures efficiency.
  3. Energy generation efficiency, the cell is the key. In addition to the usual monocrystalline silicon, polysilicon, and thin-film materials, which lead to different efficiencies of solar cells, the quality level of the cells also strongly impacts the efficiency of the panels. Common cells include A, B, and C. Grade A cells are sound and may have some scratches; Grade B cells can have defects such as slurry leaks, false markings, and broken grids. Class C cells are primarily recycled cells that may have chipped edges, large false marks, broken wires, and heavy contamination. However, these solar cells are circulating products that comply with the regulations. However, B- and C-level cell prices are low, and some companies use them. This also explains the big difference in market prices for the same 100-watt solar panels.

In summary: There are several aspects to consider when buying solar panels for your RV:

①. Choose lightweight solar panels to reduce the load on the vehicle.

②. The better the encapsulation material of the solar panel (surface material, aluminum frame, back panel, etc.), the better the heat dissipation, voltage, and corrosion resistance of the solar panel, and course, the price;

③. Choose the monocrystalline silicon with the highest conversion efficiency and pay attention to the grade of the monocrystalline silicon.

How to Extend the Life of RV Lithium Batteries

Lithium iron phosphate batteries are widely used in RV/caravan/camping/boat because of their high energy density, high open circuit voltage, high output power, no memory effect, fast charging and discharging speed, and other excellent properties.

How to use lithium iron phosphate battery? Not only safe and reliable, but it also can increase battery life.

1. Not discharged frequently and deeply

LiFePO4 batteries have almost no memory. Many users often use the battery to a minimum (relative to the minimum voltage protected by the protection board) and then charge it. This is not recommended.

Although the LiFePO4 battery discharge rate can reach 100% (at a certain temperature).

2. Do not overcharge the LiFePO4 battery for a long time

Some users often want to charge the battery for a while after fully charged, which means the battery capacity is higher.

Long-term overcharging of the RV battery will cause serious damage.

Lithium iron phosphate battery overcharging assumes the following: The battery protection board design is unreasonable.

Since our LiFePO4 battery has a BMS battery protection board, there is no need to worry.

3. Choose the right charger

The charging voltage and charging current of the charger should not be too high.

4. Effect of working temperature on lithium iron phosphate battery

The LiFePO4 battery has a wide application temperature range (e.g.: -20℃—–60℃).

It can also be used at low winter temperatures, but its capacity will be greatly reduced.

When the temperature is returned to room temperature, the capacity of the lithium battery can be restored.

LiFePO4 battery is extremely temperature sensitive. Long-term sub-zero use will greatly reduce battery life.

Long-term exposure to excessive heat (e.g., over 60 degrees), even if no explosion occurs, will greatly reduce battery life.

5. How is the LiFePO4 battery maintained?

When the LiFePO4 battery is not used or needs to be stored for a long time.

It should be charged every 5 to 6 months. And it is advisable to charge 60% -80%. Not suitable for full charging.

Of course, keeping yourself in a dry environment is also important.