What kind of battery does the solar street lamp use?

Li-ion Battery and  LiFePO4 Battery commonly used in solar lighting.

1, Li-ion Battery

Lithium ion batteries have the following advantages:

High energy density: different according to electrode materials, calculated by mass, up to 150 ～ 200Wh / kg (540 ～ 720kJ / kg); calculated by volume, up to 250 ～ 530Wh / L (0.9 ～ 1.9kJ / cm3). [2]

High open circuit voltage: It varies with electrode materials and can reach 3.3 ～ 4.2V.

Large output power: varies with electrode materials, up to 300 ～ 1500W / kg (@ 20sec).

No memory effect: Lithium iron phosphate lithium-ion battery has no memory effect, and the battery can be charged and discharged at any time without discharging electricity, which is easy to use and maintain.

Low self-discharge: <5% ～ 10% / month. The intelligent lithium-ion battery has a built-in monitoring circuit, and the working current of this monitoring circuit is even higher than the self-discharge current.

Wide working temperature range: can work normally between -20 ℃ ～ 60 ℃.

Fast charge and discharge speed

Therefore, lithium-ion batteries are widely used in consumer electronics, military products, and aviation products.

Lithium ion batteries also have the following disadvantages:

(1) Not tolerant to over-discharge: During over-discharge (discharge when the voltage is less than 3.0V), excessively inserted lithium ions will be fixed in the crystal lattice and cannot be released anymore, resulting in shortened lifespan, and deep discharge is more likely to damage the battery. Therefore, the use of extremely low power is a behavior that damages the battery, but as long as it is recharged to a high voltage several times, it is possible to reactivate the maximum storage capacity of the battery.

(2) Unable to tolerate overcharging: During overcharging, the electrode deintercalates too much lithium ions, and it is not replenished in time. It can cause the lattice to collapse for a long time, which irreversibly reduces the amount of stored electricity. Therefore, the lithium battery must be used frequently, to avoid maintaining a full charge state and to continue to plug in the charger connector, the stored electrons must be regularly flowed to maintain the long-term health of the battery.

(3) Aging and fear of heat: Unlike other rechargeable batteries, lithium-ion batteries will inevitably and slowly decline during the use cycle. Even if they are stored and not used, the capacity will decrease, which is actually not related to the number of uses (unless it is The lattice loss caused by the excessive charge and discharge cycle is more appropriate as the aging process is called loss), and it is related to the temperature. The possible mechanism is that the internal resistance gradually increases. Therefore, electronic products with high operating current are more likely to reflect the phenomenon of thermal decay. In addition, the influence of external temperature should also be avoided. Replacing graphite with lithium titanate seems to prolong life.

Therefore, multiple protection measures are required for lithium-ion batteries, such as protection circuits to prevent overcharge, overdischarge, overload, and overheating. Increase vents, diaphragms and other explosion-proof measures.

 

2. LiFePO4 Battery

Characteristics of lithium iron phosphate battery

Higher energy density

According to reports, the energy density of the square aluminum shell lithium iron phosphate battery mass produced in 2018 is about 160Wh / kg. In 2019, some excellent battery manufacturers may be able to achieve the level of 175-180Wh / kg. The film technology and capacity are made larger, or it can achieve 185Wh / kg. [4]

Good safety performance

The positive electrode material of lithium iron phosphate battery has relatively stable electrochemical performance, which determines that it has a stable charging and discharging platform. Therefore, the structure of the battery will not change during the charging and discharging process, and will not burn or explode. It is still very safe under special conditions such as charging, squeezing and acupuncture.

Long cycle life

The 1C cycle life of lithium iron phosphate batteries is generally 2000 times, or even more than 3500 times, and the energy storage market requires more than 4000-5000 times, which guarantees a service life of 8-10 years, which is more than 1000 cycles of ternary batteries Life, and the cycle life of long-life lead-acid batteries is about 300 times.

Safety and environmental protection

Lithium iron phosphate batteries do not contain any heavy metals and rare metals, are safe, non-toxic and non-polluting, and are absolutely green and environmentally friendly batteries. Because the lithium iron phosphate material is clean and non-toxic throughout the production process, all raw materials are non-toxic and non-polluting

 

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