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Battery: replacement and selection

When and why car battery needs replacement

Average lifetime expectancy of lead-acid batteries is 4 years, gel batteries can serve for up to 7 years. Amongst defects, leading to premature breakdown of these components, are housing damage, sulfation of plates, short circuit, electrolyte boiling out, polarity violation.

Breakdown of the battery can be caused by malfunction of the alternator or its belt, incorrect installation of car electric equipment, overcharge of the unit with large current, usage of incompatible electrolyte, defects of battery fasteners, improper battery charging during which polarity is violated, continuous storing of a discharged battery or repeated full discharges.

Most of all, component malfunctions manifest themselves through electric equipment failures, particularly, troubled engine starting. Decreased capacity, altered voltage values during charging and discharging also point at a defect. Besides, improper operation is indicated by too fast or too slow charging and discharging, overheating, gas formation and harsh scent from the unit. Replacement of the battery should be performed at a service station. Demounting of a defective device is laborious and requires removal of many components. Moreover, replacement of batteries with liquid electrolyte entails the risk of contacting with aggressive chemical compounds, which is very dangerous.

How to select battery

The car batteries are divided into low maintenance and maintenance-free ones. The first ones require regular control of density and level of electrolyte. The maintenance-free ones are sealed, require no servicing, are convenient and reliable, but have a higher price.

Also the batteries are divided by electrolyte state. It can be liquid, gel-like, or absorbed by a special porous substance (AGM). In the most popular batteries electrolyte is a liquid mixture of sulphuric acid and distilled water. The advantages of such devices are low price, small self-discharge and no decrease in capacity after incorrect charging.

In gel and AGM-batteries, special substances (silicon compounds and glass fiber respectively) are used to promote electrolyte thickening. This prevents its leakage and minimizes loss of active substances from electrode surfaces. These batteries have higher power and longer operational lifetime. Moreover, recombination of gases generated in chemical reactions occurs in these devices, which promotes reducing of harmful emissions.

Amongst disadvantages of the gel and AGM batteries their sensitivity to overcharge is worth mentioning; thus usage of a special charging device with small current and a stable voltage in the car mains are necessary.

When buying a car battery one should prefer devices from well-known manufacturers. Nowadays, such companies as Bosch, Varta, Exide and some others offer high-quality products.

Select the battery with a capacity, which is recommended by the vehicle manufacturer. Also consider dimensions of the unit, diameter and polarity of terminals, base height and cranking amps. Take into account that batteries for diesel cars should have significantly higher capacity and cranking amps than ones for gasoline cars.