Battery life has been defined as the time period of which it lasts for service without any damage. Battery life is reduced by overcharging which causes overheating and excessive gas bubbling. In a car, the battery can be overcharged due to a faulty generator control which causes the generator to continue to charge the battery after it is fully charged. The too concentrated electrolyte also causes overcharging. Lack of water not only makes the
electrolyte concentrated but, it reduces electrolyte level also in the cell, and thus causes disintegration of the exposed plates.
If a battery is continuously undercharged, it becomes sulfated, which causes loss of active material. It also causes the plates to buckle and break. Excessive loads, such as those produced by propelling the car with the starting motor, are detrimental to the battery life.
The battery is completely damaged if the electrolyte freezes in it.’ The freezing points of various solutions depending on the state of charge are given in the following table:
|SPECIFIC GRAVITY||FREEZING POINT (°F)|
To compensate for the loss, distilled water must be added in the battery to prevent the dissolved materials. In freezing weather, it should be added just before the car is operated to avoid having it freeze before combining with the acid. The battery life greatly depends on the material and workmanship used in making it and on the care it receives in service.
Doing this will last your battery twice long.
FACTORS AFFECTING BATTERY LIFE
Charging a battery greatly in excess of what is required is harmful in several ways, as follows:
- Decomposes water of electrolyte into hydrogen and oxygen gas. Gas bubbles capable of washing-active material from the plates and carries moisture and acid from the cells as a fine particle of mist.
- Decomposition of water leaves acid more concentrated. Concentrated acid is harmful to separators and negative plate material at high temperatures over a prolonged period of time, charring the separators and making the negative material sandy and granular.
- High internal heat is created, which accelerates corrosion of positive plate grids and damages separators. Also, containers may be softened and distorted and sealing compound displaced.
- Overcharging alone or in combination with a previous condition of undercharging may cause severe buckling and warping of positive plates with accompanying perforation of separators.
- May cause damage by corrosion to cradle, cables and other vital electrical and engine parts by forcing liquid from the cell if charging rates are excessive.
A battery working with insufficient charge over a long time period may develop a type of sulfate in the plates which is dense, hard and crystalline and which cannot be electrochemically converted to normal active material again. Such lead sulfate being less dense than the active material from which it was formed will set up strains in the positive plates so that distortion or bowing of plates, called buckling may result. Severely buckled plates will pinch the separator at the plate corners or chafe the center of the separators. This may result in perforations of an unprotected separator and develop a short circuit of the cell.
- A battery-operated in an undercharged condition is not only unable to deliver full power but is liable to freeze during severe winter weather.
- Lead sulfate formed on the plates during discharging is relatively insoluble as long as the specific gravity of the electrolyte is kept above l.125. Subsequent charging may convert these crystalline deposits to filamentous metallic lead which may short the positive and negative plates through the areas of the separators affected. These small shorts may cause a condition of low cell voltage when the battery is charging. For this reason, the battery should not be allowed to stand idle in a more than 75% discharged condition for very long periods of time.
Lack Of Water
Water is one of the four essential chemicals of a lead-acid storage battery and under normal conditions of operation are the only component of the battery which is lost as the result of charging. It should be replaced as soon as the liquid level falls to the top of the separators. If water is not replaced and the plates are soon exposed, the acid will reach a dangerously high concentration that may charge and disintegrate the separators and may permanently sulfate and impair the performance of the plates.
Plates cannot take a full part in the battery action unless they are completely covered by the electrolyte. Sulfuric acid needs never be added to a cell unless it has been lost due to spillage. Then it should be replaced only. No satisfactory substitute electrolyte has been found for the simple mixture of sulfuric acid in water. Use no substitutes.
Hold-downs, if not properly adjusted may allow the battery to bounce around in the cradle. This may cause the bridges, on which the elements rest to notch the bottoms of the separators and may cause the plates to notch the bridge tops, causing a severe disarrangement of the element.
The bouncing of the battery may also crack or wear the container badly and cause the sealing compound to open up and leak acid. Leaking acid corrodes terminals and cables: and makes high resistance battery connections, thereby weakening the battery’s power and shortening its life. Hold downs; on the other hand, can be too tight, distort or crack the container and loosen sealing compound, allowing the loss of acid from the cells: and this may cause loss of battery capacity and battery life.
A battery should never be used to propel the car by the use of the starting motor with the clutch engaged except in a great emergency. This may produce extremely high internal battery temperature and damage the starting motor.
Freezing of Electrolyte
The electrolyte of a battery in various stages of charge will start to freeze at temperatures indicated below. The given temperatures indicate the approximate points at which the first ice crystals being to appear in the solution. The solution does not freeze solid until a lower temperature is reached, solid freezing of the electrolyte may crack the container and damage the positive plates.
A 1/3 charged battery is in no danger of damage from freezing. Therefore, keep batteries better than 3/4 charged, especially during winter. This plays a major contribution to the reduction of battery life.
|SPECIFIC GRAVITY (AT 27°C)||FREEZING TEMPERATURE|
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