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The factors of affecting the life of batteries in photovoltaic power generation system

1. The positive active material softening off 
 
In the recycling conditions, the failure of battery is mainly due to that the positive active material (PAM) is softening and shedding. 
 
For lead-acid battery in recycling process, the active material of positive and negative electrode through the dissolution of the reversible re-deposition process, which changed the structure of porous lead dioxide electrode. Especially for lead dioxide electrode, it may give rise to apparent size increases, the change in particle and pore size distribution, porous structure of lead dioxide particles combined mechanical properties and electrical conductivity decreased as the cycle continues, this situation will further deteriorate, with the result of active substances in the region softening and shedding. 
 
2. The impact of discharge current on the life of battery
 
In the photovoltaic system, the battery discharge current is very small. In the condition of small current, the formation of four high-current is much more difficult than the conversion of four. This is because that the current conditions in small crystalline particles formed by four high-current conditions than the formation of four crystalline particles thick, coarse crystalline particles of 4 to reduce the effective area of 4, so that when re-filling accelerated plate polarization, lead to four into difficulties, as the cycle continues, the situation will be exacerbated with the result that can not be recharged into the electric plate, which finally led to the life end for battery. 
 
3. The battery capacity after the recovery of deep discharge
 
In the photovoltaic system, comparing with batteries used in other occasions, the battery discharge rate is low, usually ranging from 20 to 240, even lower. For a small current, the depth of discharge means that the active substances on a board will be more fully utilized. In many PV systems, the depth of discharge usually does not occur, unless the charging system failure or in a long period of bad weather. In this case, if the problem of rechargeable battery is not solved timely, the problem will become even more serious, it can lead to capacity loss. 
 
4. The impact of acid stratification on battery life 
 
The stratification of electrolyte is due to gravity's role in the process of charging and discharging for the battery, that is, charging has produced 24 surfaces of positive and negative electrode, its density is decided by gravity and sink. In the discharge, the positive and negative plate surfaces consumption of 24, so the surface of liquid layer density, low-density along the plate between the increase in the electrolyte, while the polar group of the upper part of a very high density of the electrolyte from the base to the downstream side of the electrolyte resulted in the movement of the upper low density and lower density. The stratification and generation of battery life and capacity will adversely affect the accelerated positive grid corrosion and shedding of live material, resulting in sulfation of negative plate. 
 
5. Electro-hydraulic density on the impact of lead-acid battery’s life 
 
The concentration of electrolyte is not only with the battery capacity, but also to positive grid corrosion and negative active material of the sulfate. High concentration of sulfuric acid accelerated positive grid corrosion and negative active material sulfate and lead to increased water loss. 
 
6. The impact of grid alloy 
 
Battery, due to long-term use, cathode grid in the electrolyte under the influence of the progressive corrosion raised grid to grow up to live a combination of physical and grid decreased, leading to gradual loss of battery capacity. This corrosion and grow up of positive grid are mainly caused by grid alloy composition, the electrolyte density and shape of grid ribs and other factors. 
 
In the battery charging process, the grid and active material to form non-conductive interface layer, these non-conductive layer or low-conductive layers and interfaces in the grid caused by a high-impedance, resulting in fever and board charge and discharge when the gate near the expansion, thereby limiting the capacity of the battery (so-called effect). 
 
7. The impact of the thickness of plate 
 
The thickness of plate should fall within the battery design in general, the cycle life of thick plate is longer than thinner plates, while the utilization of active material compared to some worse. However, it can help extend the life cycle of the loop. 
 
8. Assembly of the pressure shadow 
 
Assembled battery life with relentless pressure on the major impact of partition flexibility to poor assembly, very non-pressurized or pressure groups too small partitions and plates can not maintain good contact and the battery capacity dropped significantly. 
 
In the cycle, the active material with expansion, loose, fall off the end of the battery life of one of the reasons in advance, while the assembly of a higher pressure can prevent the active material in the deep loop in the process of expansion. If the assembly pressure is too low, it will also lead to premature clapboard with plate separation of the difficulties which caused by electro-hydraulic transmission, the battery internal resistance increases rapidly, easily lead to battery end of life. Therefore, using a cell assembly with high pressure can keep the assurance of long cycle life. 
 
9. The impact of temperature 
 
High-temperature dehydration of the battery dry, hot out of control, positive grid corrosion and deformation and so the effect of accelerating the role of low temperature will cause negative failure, temperature fluctuations will be accelerated dendrite short circuit, etc., which will affect battery life. Discharge in a certain range of ambient temperature, the use of the capacity increases with increasing temperature, with the lower the temperature decreases. At ambient temperature within 10 ~ 45, lead battery capacity increases with increasing temperature, such as valve-regulated lead-acid batteries discharge capacity at 40 than at 25 large discharge capacity of about 10%, but above a certain temperature range, on the contrary, if the ambient temperature within 45 ~ 50 under the conditions of discharge, the battery capacity significantly reduced. Low temperature (<5), the battery capacity decreases as temperature decreases, the electrolyte temperature decreases, its viscosity increases, the ion transport \ move by a lot of resistance, diffusion capacity to reduce the electrolyte resistance at low temperatures also increase large, the resistance of electrochemical reaction increased, resulting in decreased battery capacity. Second, low temperatures will also lead to decreased utilization of active material negative impact battery capacity, such as the battery in -10 ambient temperature discharge, negative plate capacity of just over 35% of the rated capacity. 
 
Under normal circumstances, if at 25 under the conditions of use, battery life of three years, then 30 under the conditions of use, it fell to 2.5 years, 40 when it fell to 1.5 years. That is 25 as the base is increased by 10, its life shortened by half.


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