Batteries usually have a life expectancy of about 3 to 5 years, this can vary. If your Battery is serviceable the water level should be checked while your vehicle is in for service. Maintenance free Batteries are not serviceable. Running your vehicle with a weak Battery can cause many problems. If the correct amperage is not being produce by your Battery then it will use the Alternator to charge, which will drain your Alternator and Battery. If you have known issues with the Battery Charging it's not recommended running or cranking your vehicle until the Battery is replaced. Some Computer controlled devices can be damaged if ran with a weak or bad Battery or Alternator. This can all be avoided. Batteries or Alternators may or may not give your prior warning to the expiration. Your vehicle should not be operated with either the Battery or the Alternator not working correctly. Battery terminals that are loose or damaged can produce low amperage and sometimes will not crank your vehicle. Battery Cables can do the same. If your charging light comes on or the gage shows that it has dropped below what it normally runs then you should take your vehicle to a Repair Shop then to avoid a towing. Voltage Regulators must be working properly as well.
Alternators
Alternators are the key to keeping the Charging System Charging. They are belt driven and charge your system while running the engine. Belts that break or become too loose will result in the Alternator failing to Charge which will cause your Battery to drain and possible failure to the Alternator and Battery may occur. Sometimes Alternators that go bad by them self without another cause will whine or squeal. If your Alternator fails and your Battery fails your engine will not run without them.
Starters
Starters may or may not give you a warning sign of having problems. Usually you will get a click when you try to crank and sometime you can hear the Starter trying to engage but fails. Your Vehicle will not go without the Starter performing it's job to crank the engine.
