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Types of lead-acid batteries for photovoltaic energy storage systems
- Jul 30, 2018 -

There are many types of lead-acid batteries, which are used in photovoltaic energy storage systems. There are three kinds of lead-acid batteries, rich liquid lead-acid batteries, valve-regulated sealed lead-acid batteries, lead-carbon batteries and so on.

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1. Rich liquid lead-acid battery

The sulfuric acid in the electrolyte of the lead-acid battery directly participates in the charging and discharging reaction process of the battery. In the traditional lead-acid battery, the remaining space of the electrode plate, the separator and other solid assembled components in the battery cell is completely filled with the sulfuric acid electrolyte, and the electrolyte is in surplus. Excessive state, so called "rich liquid" battery, the battery plate is completely immersed in the sulfuric acid electrolyte. The top of the flooded battery has a cover that can be ventilated and can block the liquid from spilling. Due to the evaporation and decomposition loss of water during use, it is necessary to periodically open the lid to add distilled water and adjust the electrolyte density, so it is customary to be called It is an "open" battery.

Rich liquid lead-acid batteries are characterized by low price and long life, and the disadvantage is that they require frequent maintenance.

2. Valve-regulated sealed lead-acid battery

Valve-regulated sealed lead-acid batteries, also known as maintenance-free batteries, are classified into AGM sealed lead batteries and GEL colloid sealed lead batteries.

The AGM type battery uses a pure sulfuric acid aqueous solution as an electrolyte, and most of it exists in the glass fiber membrane, and a part of the electrolyte is sucked inside the electrode plate. The AGM type sealed lead storage battery has a small amount of electrolyte, the thickness of the electrode plate is thick, and the utilization rate of the active material is lower than that of the open type battery, so the discharge capacity of the battery is about 10% lower than that of the open type battery.

AGM sealed lead batteries have a lower discharge capacity than today's colloidal sealed batteries. Compared with the battery of the same specification with rich liquid type, the price is higher, which has the following advantages:

(1) The cycle charging capability is 3 times higher than that of lead-calcium batteries, and has a longer service life.

(2) Higher capacitance stability throughout the life cycle.

(3) The low temperature performance is more reliable.

(4) Reduce the risk of accidents and reduce the risk of environmental pollution (since the acid is 100% sealed).

(5) Maintenance is simple and reduces deep discharge.

Colloidal lead-acid battery (GEL type battery), colloidal lead acid battery is the improvement of ordinary lead-acid battery for liquid electrolyte. The electrolyte is replaced with colloidal electrolyte, which is better than ordinary battery in the aspects of safety, storage capacity, discharge performance and service life. The electrolyte is made of silica sol and sulfuric acid. The concentration of the sulfuric acid solution is lower than that of the AGM type battery, and the amount of the electrolyte is more than that of the AGM type battery, which is equivalent to the liquid rich battery. The electrolyte exists in the colloidal state and is filled between the membrane and the positive and negative poles. The sulfuric acid electrolyte is surrounded by the gel and does not flow out of the battery.

The advantages of colloidal sealed lead-acid battery are as follows:

(1) The rate of leakage of acid is small. The GEL type colloid battery has no free electrolyte after the electrolyte gel, so the risk of acid leakage is much smaller than that of AGM type battery.

(2) Less water loss. Because it has more perfusion than dilute sulfuric acid and less water loss, the gel battery will not fail due to loss of water.

(3) Prolong battery life effectively. The injection of colloid increased the strength of the baffle plate, protected the plate and made up the defects of the clapboard, which made the assembly pressure less reduced is one of the reasons for its prolongation of battery life.

(4) Colloid lead-acid battery has strong resistance to overcharge.

(5) The recovery ability of the serious discharge is strong. The gel fills the gap between the separator and the plate, reduces the internal resistance of the battery, and improves the charging acceptance ability.

Therefore, the over discharge, recovery ability and low temperature charge and discharge performance of the gel battery are superior to those of the AGM battery.

(6) The self discharge performance of the body lead acid battery is good. The storage time of the battery can be extended more than 2 times under the same purity and water quality of the same sulfuric acid.

(7) Under the condition of serious power shortage, the colloid lead acid battery has obvious anti sulphidation property.

(8) Colloidal lead-acid batteries have good discharge performance at later stage.

3. Lead carbon battery

Lead-carbon battery is a kind of capacitive lead-acid battery. It is a technology evolved from the traditional lead-acid battery. It is added with activated carbon in the negative electrode of lead-acid battery, which can significantly improve the life of lead-acid battery.

Lead carbon batteries are a new type of super battery that combines the advantages of both lead acid batteries and supercapacitors:

(1) It not only takes advantage of the ultra-capacitor instantaneous large-capacity charging, but also exerts the specific energy advantage of the lead-acid battery, and has very good charge and discharge performance.

(2) Extended battery life. The addition of carbon (graphene) prevents the sulphation of the negative electrode, improving one of the factors of battery failure in the past and prolonging battery life.

(3) The cost of electricity is reduced. 

Lead carbon battery is the most advanced technology in the field of lead-acid batteries, and is also the development focus of the international new energy storage industry. It has a very broad application prospect. It is widely used in energy storage fields such as photovoltaic power storage, wind power storage and power grid peak shaving.