battery for car bad or good?

look at the voltage as you try to start the car

If it drops off a lot then there is a good chance the battery needs replacing

However before you get a new one do as previous answer

Look at the voltage before you start the car (it should be around 12v)

now start it and check the voltage again - it should have gone up 1-2V

If it dont then most likely the alternator needs replacing

(or if you can - change the controller on the end of it

This is a lot cheaper than a whole alternator and you may not need to remove the alternator to change it - try a scrap yard for a replacement alternator then just remove the controller from it)

If the battery is 5 years old, replace it.

If the battery is 4 years old, it's getting old and when the temperature gets low the battery had problems delivering current. Best to replace it as car batteries never deliver as much current when cold as they do when warm, and you do not want to be stranded somewhere with a cold battery.

If the battery is 3 years old or younger, get a warranty replacement.