When charging, lead sulfate forms lead oxide, and when discharged, lead oxide is reduced to lead sulfate. While the lead sulfate is a very easy crystallization, when lead sulfate concentration of electrolytic solution in the battery is too high or the static idle time is too long, will "hold" group, a small crystal, these small crystals of lead sulfate to attract around, like a snowball formation of crystalline inert large, lead sulfate crystallization after charging not only can not be reduced to be attached to the precipitation of lead oxide, electrode plate, electrode plate caused a decline in the work area, this phenomenon is called vulcanization, it is often said that the aging. At this point the battery will gradually decrease until it is unusable. When a large amount of lead sulfate is piled up, the lead particles are attracted to form a lead branch, and the lead bridging between the positive and negative plates causes a short circuit of the battery. If the plate surface or seal molded case has a gap, lead sulfate crystallization will accumulate in the crevice, and expansion of tension, the plate broken off or rupture, causing irreparable physical damage to the battery. Therefore, the main mechanism leading to the failure and damage of lead-acid batteries is the unavoidable vulcanization of the battery itself.
2, the reasons for the special working environment of electric bicycles
As long as the lead-acid batteries, in the use of the process will be vulcanized, but the lead-acid battery lead-acid batteries in other fields than the electric bicycle use has a
longer life, this is because the lead-acid battery electric bicycle has an easier curing work environment.
Deep discharge
The lead-acid batteries used in automobiles are only unidirectional discharge at the time of ignition, and the power generation opportunity is automatically charged to the battery without causing a deep discharge of the battery. The electric bicycle can not be charged when riding, often more than 60% of the depth of discharge, deep discharge when the concentration of lead sulfate increases, sulfide will be quite serious.
Large current discharge
Electric car 20 kilometers cruising current is generally 4A, this value has been higher than other areas of battery work current, and speeding overload electric vehicle work current is greater. Battery manufacturers have carried out cycle life tests on 1C charging 70% and 2C discharge 60%. After this kind of life test, the battery can reach 350 times of charge, discharge and cycle life, but the actual effec
t is very different. This is because the high current work increases the discharge depth by 50%, and the battery accelerates the vulcanization. Therefore, the battery life of the electric tricycle is shorter, because the body of the three wheeled motorcycle is too heavy, and the working current is above 6A.
Charging and discharging frequency is high
In the field of battery backup power supply, only when blackout
will discharge, if a year to stop 8 times, to reach 10 years of life, only 80 cycles charge life, and electric cars a year more than 300 times the charge discharge cycle is very common.
Short time charging
As the electric bicycle is transportation, not chargeable time, within 8 hours to complete the 36 or 48 volt 20 ampere hour charging, it must increase the charging voltage (typically a single 2.7~2.9 V), when the oxygen evolution voltage exceeds the charge voltage of single battery (2.35 volts) or hydrogen (voltage 2.42 volts), the battery will be due to excessive oxygen evolution and open the exhaust valve, causing water loss, the electrolyte concentration increases, increase the curing phenomenon of the battery.
After discharge, it can not be charged in time
As a means of transport, charge and discharge of electric bicycle is completely separated, it is difficult to discharge after charging and discharging conditions in a timely manner, after the formation of a large number of lead sulfate if more than half an hour without charging for reduction of lead oxide, sulfide crystals will form.
3, lead battery production reasons
In view of the specialty of lead-acid batteries for electric bicycles, various methods have been adopted by battery manufacturers. The most typical way is as follows:
绿驹电动车电池Increase the plate number.
The original design of the cell 5 tablets 6 to 6 tablets 7 tablets, 7 tablets 8, 8 or even 9 tablets preparation. The battery capacity is increased by reducing the thickness of the plate and dividing the plate and increasing the number of plates.
Increasing the specific gravity of sulphuric acid.
The proportion of the original sulfuric acid battery float is generally between 1.21~1.28, while the proportion of sulfuric acid electric bicycle battery generally in the 1.36 to 1.38 or so, this can provide a larger current, improve the battery initial capacity.
Increase the amount and proportion of lead oxide, the active material of positive plate.
Increasing the lead oxide increases the electrochemical reaction involved in the discharge, and also increases the discharge time and increases the battery capacity.
Through these measures, the initial capacity of the battery meets the capacity requirements of the electric bicycle, especially the improvement of the large current discharge characteristics of the battery. However, as the plate is increased, the capacity of the sulfuric acid is reduced, the battery heating causes a great deal of water loss, and the probability of short circuit and lead bypass is increased. Increasing the specific gravity of sulfuric acid increases the
initial capacity of the battery, but the sulfidation is more serious. One of the most basic principle is sealed battery positive plate of oxygen, oxygen directly to the negative electrode plate, negative plate is absorbed and reduced to water, the technical indicators of the assessment parameters of the battery is called "sealed reaction efficiency", this phenomenon is called "oxygen cycle". In this way, the water l
oss of the battery is very small, and the "maintenance free" is achieved, that is, no water. Therefore, the capacity of the negative plate is required to be larger than that of the positive plate, which is also called the negative pole transition. The increase of positive plate active material will inevitably reduce the negative pole transition, the oxygen cycle becomes worse, the water loss increases, and it will lead to sulfide. Although these measures increase the initial capacity of the batteries, they can cause dehydration and sulfuration, while dehydration and sulfuration can contribute to each other, resulting in the loss of battery life.
There is a group of weld assembly problem. The place is easy to produce weld plate. Each battery cell has 15 plates, 15 solder joints, a battery of 6 cells, there are 90 solder joints, a battery consists of 3 12V batteries, there are 270 solder joints. If there is a spot weld, the cell capacity decreases, and the formation of single cell backward, cause the entire battery backward, the battery will cause serious imbalance, so that the battery failure in advance. Even if the weld control in 1/10000, an average of 37 per set of batteries will have a battery of weld, this is absolutely not enough to allow the. The lead calcium alloy grid battery in the welding time will precipitate calcium and cover weld, so, many grid battery
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