Battries

Automotive battery

An automotive battery is a type of rechargeable battery that supplies electric energy to an automobile.^[1] Usually this refers to an SLI battery (starting, lighting, ignition) to power the starter motor, the lights, and the ignition system of a vehicle’s engine. An automotive battery may also be a traction battery used for the main power source of an electric vehicle.

Automotive SLI batteries are usually lead-acid type, and are made of six galvanic cells in series to provide a 12 volt system. Each cell provides 2.1 volts for a total of 12.6 volt at full charge. Heavy vehicles such as highway trucks, often equipped with Diesel engines, may have two batteries in series for a 24 volt system, or may have parallel strings of batteries.
Lead-acid batteries are made up of plates of lead and separate plates of lead dioxide, which are submerged into an electrolyte solution of about 35% sulfuric acid and 65% water.^[2] This causes a chemical reaction that releases electrons, allowing them to flow through conductors to produce electricity. As the battery discharges, the acid of the electrolyte reacts with the materials of the plates, changing their surface to lead sulfate. When the battery is recharged, the chemical reaction is reversed: the lead sulfate reforms into lead oxide and lead. With the plates restored to their original condition, the process may now be repeated.

Fluid level

Car batteries using lead-antimony plates would require regular watering top-up to replace water lost due to electrolysis on each charging cycle. By changing the alloying element to calcium, more recent designs have lower water loss unless overcharged. Modern car batteries have reduced maintenance requirements, and may not provide caps for addition of water to the cells. Such batteries include extra electrolyte above the plates to allow for losses during the battery life. If the battery has easily detachable caps then a top-up with distilled water may be required from time to time. Prolonged overcharging or charging at excessively high voltage causes some of the water in the electrolyte to be broken up into hydrogen and oxygen gases, which escape from the cells. If the electrolyte liquid level drops too low, the plates are exposed to air, lose capacity, and are damaged. The sulfuric acid in the battery normally does not require replacement since it is not consumed even on overcharging. Impurities or additives in the water will reduce the life and performance of the battery. Manufacturers usually recommend use of demineralized or distilled water since even potable tap water can contain high levels of minerals.



Car Battery Testing

The only way to gauge a battery's performance is to test the voltage output it is offering. The output voltage levels that it provides with and without load can give you an idea of battery health.

So to test a car battery, arm yourself with a voltmeter and set the dials on the 0-50 V range. Disconnect the battery from the car connections by following the details in the car manual to the word. While doing so attach a 9V alkaline battery to the car PCM as otherwise it loses its programmed settings.

Connect positive red lead of voltmeter to positive of battery terminal and the black lead to the negative terminal. Check the voltage level. If its in the range of 12.6 to 12.8, your battery is doing well and adequately charged. Anything below that like 10 V or lower means it is in need of charging.

Now reconnect the battery and start the car. Keep it in idling mode and check the voltage reading between the same points again. If it is around 10V, then the battery is okay. Anything below 10 V means that either the car battery needs charging, or some other problems are causing the voltage decline.

Next thing to check is the fluid levels in the battery. To do this you must disconnect the battery again of course. Open up the battery cover and peep into the compartments of cells inside. The electrode plates should be submerged in the electrolytic fluid. If they are not, you must add distilled water to the cell compartment only uptil the fluid level rises about a one fourth of an inch above the plate. Another reason causing low battery charging may be, due to car alternator problems. Get it checked with the mechanic as soon as possible