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Detailed guide to solar panel battery - basic knowledge and how to choose
What are the components of a solar energy storage system?
Solar energy storage system usually includes the following components:
① Solar Panels
The solar panels function as sunlight harvesters and convert the solar energy into DC electricity.
② Inverter
The purpose of the inverter is to convert DC electricity produced by the solar panels into 240V AC electricity, which powers appliances and electronics.
③ Batteries
Batteries store the energy generated during the day through solar panels. The energy stored in batteries provides power during the night or in the absence of grid energy.
④ Charge Controller
The charge controller regulates the flow of electricity between solar panels and batteries to ensure that the electrical power stored in the battery does not exceed the range of current and voltage parameters that the battery can withstand. Their function ensures a safe charging/discharging process and boosts the lifespan of batteries.
⑤ Other Components
Numerous components are required to build a solar storage system, including circuit breakers, switchgear, electrical conduit, mounting hardware, battery enclosures, AC/DC disconnects, and safety equipment.
What are solar panel batteries?
Solar energy storage works by adding a battery to the solar system. The battery storage in a solar system serves two primary purposes:
① Have backup power in case of grid failure
② The stored solar energy can be used to generate electricity at night so as to reduce their electricity bills by utilizing Time-of-Use rates
Introduce four types of batteries that used with solar panels
Solar batteries primarily have four types:
① Lithium-ion
Lithium ion solar battery is popular among residential homeowners. There are three reasons for this:They have a longer lifespan and require less maintenance. They are lighter and smaller compared to lead-acid batteries.
In addition to these features, these batteries can discharge to 20% SOC, which means they have a higher usable capacity. However, lithium-ion batteries carry the risk of thermal runaway, and they may catch fire if not installed properly.
② Lead-acid
Lead-acid batteries are the oldest type of solar cells. It comes in two different types: sealed lead-acid batteries and water-immersed lead-acid batteries. Lead-acid batteries are the least expensive of the four types of batteries.
However, in terms of functionality, lead-acid solar batteries generally have a shorter life span, have a lower discharge capacity compared to other storage options, and also require regular maintenance.
③ Nickel–cadmium
NiCd batteries are able to operate at extreme temperatures without complex battery management system. This is why they are popular in commercial scale projects. However, due to their high toxicity, they are banned from use in many countries.
④ Flow
Flow batteries are a new storage solution for solar battery technology with long cycle life. Moreover, they are water-based and non-toxic.
However, its technology is still in the development stage and is more expensive than other options. The storage capacity is small and takes up a lot of space.
Which battery is best for solar panel?
Lithium-ion batteries such as LFP (LiFePO4) and NMC (LiNiMnCoO2) are preferred in solar energy storage systems. LiFePO4 batteries have a long cycle life, making them ideal for off-grid installations.and they are also perform exceptionally well in regions with extreme temperatures.
How long do solar batteries last? What is the longest lasting solar battery?
Most solar batteries on the market today will last somewhere between 3-10 years. Three types of batteries are commonly used in solar storage: lead-acid, lithium-ion, and flow. Of these three options, flow batteries last the longest, but they cost a lot, have a low energy density and occupy a lot of space.
Lithium-ion batteries will also last long. It may last 5-10 years(the premise of one cycle per day). But keep in mind that quality maintenance efforts can definitely impact how long your solar battery will last.
How to calculate how many Wh of solar battery and solar panels do I need?
Three necessary calculations must be made to determine a suitable solar storage system, which are given below:
Load Wattage:
First is the estimation of load wattage, which is the total amount of electricity required to power the appliances. For a device that uses 100 Watts and runs 10 hours per day, the load wattage can be calculated by the below equation:
100 Watts x 10 Hours = 1000 watt-hours
Solar Panel Specifications:
Solar panels are rated in watts according to the electricity they can produce in a single hour of direct sunlight. The amount of sunlight exposure should not be overestimated as its availability varies according to the season and weather of the region.
For example, if sunlight is available for 5 hours per day, the Wattage requirements for solar panels can be calculated by the following equation:
1000 watt-hours ÷ 5 hours = 200 watts (a 200 watts solar panel)
Battery Requirements:
Once power requirements and solar panel specifications are determined, the next step is the estimation of battery storage.
For choosing the correct solar battery, the calculation of Amp Hours (Ah) rating of the battery is carried out by following the equation:
1000 watt-hours ÷ 12 V = 83.33 Ah
What are the pros and cons of lithium-ion solar batteries?
Lithium-ion solar batteries are promising energy storage mediums. LiFePO4 is a type of lithium-ion batteries available on the market suitable for solar energy storage systems.
Pros of lithium-ion batteries
Lithium-ion batteries are compact and demand no maintenance. They have a higher energy density and a longer lifespan. Lithium-ion batteries can provide between 2,000 and 4,000 cycles over 80% DOD.
Cons of lithium-ion batteries
Li-ion batteries are relatively more expensive than their counterparts. They also require a stabilizing circuit to ensure safe operation.
Introduce the different specifications of the common lithium ion battery for solar panel
| Specifications | Description |
|---|---|
| Solar Battery Capacity/Ratings | The power rating is the capability of the battery to supply energy. It is measured in kilowatt-hours (kWh). |
| Solar Battery Voltage | Batteries are marked with nominal voltage. It is the average value of the working voltage during the whole discharge process. Lithium-ion batteries have the highest cell voltage of all types of batteries, between 3.2-3.7V. |
| Round trip efficiency | A solar battery’s round trip efficiency is a ratio of the energy charged to the battery to the energy discharged from the battery. It is typically between 85~98% in lithium ion battery. |
| Charge/Discharge | The charge or discharge c rate is expressed as a ratio of the battery capacity (C) to the charge or discharge time period in hours. |
| Storage Procedure | Recommended temperature range for storage: -20°C to 60°C. |
| Battery Life Expectancy | Battery lifetimes are measured with three metrics: expected years of operation, cycle life, and expected cycles. The expected lifespan can be estimated by dividing the number of cycles by the number of days per year. |
| Operating Temperature | The Operating Temperature of Lithium-ion is between 20°C and 60°C. |
| Safety/Environmental Concerns | All solar batteries must meet specific safety requirements to be certified for installation. |
How efficient are solar panel batteries in winter?
In cold weather, the charging and discharging performance of lithium-ion batteries is affected. The solution to this challenge is BMS (battery management system), which uses the power to warm the battery pack before starting the charging process.
This makes lithium solar batteries an excellent performer in the winter season compared to their counterparts.
How many batteries does it take to power a house with solar?
Solar batteries are becoming essential for homeowners depending on their intended use of solar energy storage systems.
Considering an average solar battery size of 10 kilowatt-hours (kWh), the estimate of the number of dedicated batteries can be described as follows:
① Saving money: A house will require 2-3 batteries to cut the cost of electricity bills.
② Resiliency: In case of sustaining power when the grid is down, then grid resiliency is achievable only with 1 solar battery.
③ Self-sufficiency: A house can become self-sufficient with 8-12 solar batteries when the purpose is to go off-grid completely.
How much do lithium ion solar batteries cost?
The current average cost of lithium-ion solar battery varies with the brand and specifications.
Popular lithium ion solar battery brands
| Battery brand | Store energy | Warranty | Price |
|---|---|---|---|
| Tesla Powerwall 2 | 13.5 kWh | ≥10-year | $12,000 |
| Enphase IQ | 3.4-10.5 kWh | ≥10-year | $3,000 and $8,000 |
| LG Chem RESU 10H | 9.8 kWh | ≥10-year | $10,000 |
| BYD Battery-Box HVS | 5.1-12.8 kWh | ≥10-year | $3,000 to $7,000 |
| Tycorun Energy T-EES5510 | 10-20kWh | ≥10-year | $3289 |
How to choose the best solar battery for your needs?
The choice of the best solar battery type is defined by personal requirements, in addition to the technical features of the battery.
Below are the essential aspects to consider for narrowing down the choice of best solar battery.
| Personal Needs | Technical Features of Solar batteries |
|---|---|
| Geography and climate | Energy Capacity |
| Energy production | Round-trip Efficiency |
| Lifestyle | Battery Lifetime and Safety |
