It isn't always easy to tell if it is the battery, the alternator, or the starter.
If the car is trying to turn over - sounds like whirrrrrr in a steady flow - it isn't likely to be the battery.
If the car lights are bright it probably isn't likely to be the battery.
If the car is trying to turn over - sounds like whir...........whir.........whir...... - it could be the battery.
No matter how you look at it, it is going to be something. If the alternator packed it in, it may have taken out the battery along with it. If the starter packed it in and you kept trying to turn the car over repeatedly you may have killed the battery.
Are the connections clean and tight? .
A good battery should read around 12.9 volts on a voltmeter with the car off.
A good alternator should read around 14.4 volts on a voltmeter (on the battery terminals) with the car on.
If the voltage drops below 9 volts during start up, the battery is failing,
We can test your battery for free and tell you if your alternator is working.