Every mechanical creation needs a source of energy to power its movement. In case of the car's electrical system, the power source is the battery, which supplies electric power to everything from the headlights, stereo, air conditioning, to the ignition system. So you can imagine what may happen when the battery dies out. Modern cars have on board computers to monitor and control each and every function. With a dead battery, almost nothing works in a modern automobile. So if you don't want to be in a situation where you have to literally push your car home, then you should know when to replace the battery. Like every car part, even batteries have a limited lifespan.
All car batteries are electrochemical cells, bunched together in series, providing around 12 V of battery output. Each one of them is made up of lead and lead oxide electrodes dipped in diluted sulfuric acid. Electric current storage and supply is carried out by the chemical reactions that occur inside. These batteries are rechargeable and are charged by the alternator, which in turn is driven by the car engine.
Symptoms of Imminent Failure
To know how well a battery is performing, you need to know its testing method. Armed with a voltmeter, check out its voltage output, with and without applied load. If it drops substantially below 12 V without load, you can be assured that there is a dip in performance. A major reason for the drop in performance is sulfation, which is crystallization and deposition of lead sulfate inside the battery, in the course of operation.
Besides the dip in voltage output, a sure sign of a battery in need of replacement is a cracked outer case, which exposes the electrolyte stored inside, to the external atmosphere. Besides this, there may be corroded terminals and broken electrode plates.
The Ideal Timing
There is no fixed rule as such, about when to go for a replacement. A lot depends on the usage, quality of the battery, weather conditions of usage, and the level of maintenance you engage in. If you notice any of the bad signs and symptoms listed above, it is time for you to start looking for a replacement. When the battery is past its warranty period, it is not even economically reasonable to spend on repairs. It's best that you invest that money in buying a new one instead.
If you consult expert mechanics, they will recommend a battery change every 3 to 4 years. That's the amount of time for which they normally maintain good performance levels. It is the average life expectancy. The chemical reactions that occur inside the battery limit its life and after a point of time, voltage levels drop due to internal wearing out.
The best way to decide the replacement timing is to inspect the battery on your own and look for signs. If you see damage and a drop in performance levels, it's best to get it replaced as it won't cost a lot and it's not worth taking a risk. To conclude, the average life is four years and if your battery is past it, you should directly go for a replacement.