I just did my volt guage and I have a yellow top battery. When the car isn't on and the radio and everything is on my meter reads 13v and when I am driving it reads 14.5v. I have 2 12inch subs 3 TVs and a 600 watt amp!
Is this normal?

 

13.0 is a bit on the high side with the engine off, but it may be normal for a new or very good condition battery. Normal is 12.6 to 12.8 volts.

14.5 is normal with the engine on. That is the charge voltage for the maxima. It may be a slight bit lower when it is warmer out because it's easier to charge a warm battery than a cold battery.

 

So what is the normal range for battery voltage to fluxuate during startup, sub use, and driving? I'm installing a battery volt gauge soon and would like to know what to look out for.

 

Fully charged battery is 12.7 volts or more, 80% charge is 12.42 volts, 60% charge is 12.2 volts, 40% is 11.9 volts, 20% is 11.6 volts.

With engine running and charging voltage should read between 12.8 volts and 15 volts. Batteries can charge faster at higher temps and have can discharge faster. A warm battery is better for starting the car, therefore keep it in the engine compartment. Start up voltage will depend on the condition and size of battery, internal resistance, and wireing condition and quality.

Battery voltage with stereo running will depend on many things such as accesory drain, stereo drain, lights, heat, A/C, etc. You also must consider the quality and condition of the wireing.

If voltage while driving drops below about 13.2 you are likely overtaxing the alternator. But if this only happens at idle or for low bass notes I wouldn't worry about it. Otherwise look into upgrading the wireing or other electrical system upgrades.

 

Exactly what I was looking for, thanks.