Your vehicle has a battery for a very good reason – it offers the initial power required to crank the engine and get the vehicle running. After that, the alternator takes over, offering the power for your accessories, as well as recharging the battery. If your battery has gone bad and then recharged, and you’ve realized that it will not hold a charge (the battery is good for a little while, but then the charge dissipates), there’s an issue somewhere in your system that must be diagnosed and repaired.
How the battery system works:
In a normal system, it works like this: Your battery gives power to the starter and the main relay. The main relay energizes the fuel pump and computer. The battery also feeds the initial electric spark to the spark plugs. Once the engine is cranked, the alternator starts turning, which produces the electricity necessary to recharge the battery and to power the engine and other parts.
The alternator should always offers enough electricity to recharge the battery and power your other parts. If it does not, then the electricity requires comes from the battery and because it’s not being recharged, it will eventually die. Of course, automotive batteries has a limited lifespan – they should be checked often after they’re about three years of age (although it’s advisable to have them checked at least twice a year no matter how new they might be).
If your battery won’t hold a charge, it means there are issues within the system that are either keeping the battery from being recharged, or draining the battery when the engine is off.
Common reasons why this happen:
- Bad Cell: Batteries will eventually die no matter what you do. They will develop a bad cell that keeps them from holding a charge and will have to be replaced. This is part of normal car maintenance. Have your battery tested every Spring and Fall to ensure that you’re able to keep from being stranded by a failed battery. Batteries most commonly “die” during hot and cold weather.
- Low Water: Some batteries have fill holes that let you to maintain them, although most modern batteries are maintenance free and don’t let you to add water. If you have a maintainable battery, topping off the water level may solve the issue.
- Faulty Alternator: If the alternator is not charging the battery while the engine is operating, the battery will not hold a charge. This is most seen if you jump the battery and the engine runs for a while, only to die again. It is also observable by watching your headlights – while the engine is running, check the lights. If they begin bright but slowly fade, chances are good that the issue is the alternator, not the battery.
- Corroded Battery Cables: Battery cables and terminals can also suffer from corrosion. As it builds up, this corrosion keeps solid contact, and can limit the charge being supplied to the battery from the alternator. Regular maintenance of your battery can stop this.
- Loose Alternator Belt: If the alternator belt gets loose (old and stretched), it will not propell the alternator properly, which means that the charge the alternator generates may not be enough to recharge the battery.
- Parasitic Drain: It might equally be that your battery and alternator are just fine, but there’s something else draining the charge. This could be something as simple as keeping the lights on, or having an accessory plugged in to an “always on” power outlet, or it could better yet be a stuck relay or something else that’s pulling power from the battery when the engine isn’t running.
How it’s done:
The mechanic will test your vehicle battery, alternator and starter. The mechanic will also check for parasitic drain and other issues that might make your battery not hold a charge. It may be necessary to change your battery in order to diagnose other system-wide problems (if the battery has developed a bad cell).
How important is battery diagnoses?
If your battery won’t hold a charge, it’s not safe to drive your vehicle. Even if your alternator is working fine, turning the vehicle off for something as simple as stopping at the gas station will mean that the engine won’t crank and you’ll have to jump it off.
SEE ALSO:WHAT TRIGGERS ON THE BATTERY LIGHT