How to tell if my battery is going bad?

[LuckyTaxi]

My dashboard indicator shows I have between 9V and 18V (I would say it's around 12V).
Lately, I've noticed that my car doesn't want to cut over when I start it up. It's much more noticeable in the morning but I notice it a bit if I'm going out for lunch or I leave work to go home. It'll cut over on one crank but it seems very sluggish to me. I also noticed as I'm turning the key and the engine does it's thing, all my lights go dim but eventually once the car is running, everything seems fine.

Bad starter or battery going bad?

 

[LTC8K6]

If the battery is 5 years old or more, you probably need a new one anyway.

If not, then you can get it tested for free at Auto Zone or Advance Auto.

You can also test it yourself if you have a meter and know how to use it.

You want about ~12.5 volts with the car off and about ~14 volts with the car running.

 

[LuckyTaxi]

car off as in, turn the ignition one click over so that just the radio works? and then see where the indicator hits?

 

[LTC8K6]

That will work if you trust your dash meter. It's often hard to get a precise reading on a dash meter, though.

You should really use a multimeter set on DC Volts and measure at the battery terminals with the key off.