Will running my car radio for an hour using ACC drain my battery?

Question

I have a 2002 Mustang with the upgraded Mach sound system.

Answer 1

Hello, to answer your questions, you should add more information.
But let's assume things you didn't mention, maybe this helps you to calculate with the same method.
Case 1:
I Assume you have a battery no more than 75 Ah capacity. This means that a fully charged specimen (approx 12.7 Volts quiescent) discharged with 25 Ampers till 10.5 Volts (no 12V batteries may be drained below this voltage !), takes approx. 120 minutes. this is called the 'reserve capacity' of your battery. During discharge, the voltage of the battery drains. With a 75Ah, 680 Ampers CCA (EN) starting current (these are very general, baseline features), you have a chance to start your engine when the battery voltage is above approx. 12.0-12.1 Volts.
To reach this state of charge, you can load your battery approx. 45-50 minutes. We calculated with 25 Amps during discharge, we can count with an average voltage of 12.3 V available for your radio. 12.3 X 25 Amps equals an average available momentary power of 300 Watts. This consumption (current flowing from the battery) depends on the volume and the power requirements of the amplifiers. For a 4X50 Watts head unit, the required power is less than 300 W (but more than 200 W -> losses). So with a typical 75 Ah battery at fully charged is capable to power your radio for more than 45-50 minutes.

Case 2: you have a spiral cell battery in your Mustang, like an Optima Red Top, or an Exide Maxxima. They have larger starting currents (min. 800 A in EN standard), but they have only a capacity of 55-60 Ah. They have very good cyclic properties and offer less distortion in hi-fi application because they can better supply heavy transient loads (like basses in the music). What's important, that e.g. an Optima 1050 60 Ah battery has a reserve capacity of approx. 120 minutes, an Exide Maxxima has approx 95 minutes when new. Thus, with a spiral cell battery this approx 300 Watts still OK for 45-50 minutes, for spiral cell batteries the starting ability does not depend so badly from voltage -> when a bit oversized for the application, even below 12 V is possible to start.

Be warned: the cyclic use of starter batteries heavily degrades the life cycle (capacity, starting ability) of these batteries !!! You can do it once or a few times, but don't do it often. After a draining, immeadiately recharge your battery ! A starter battery must be kept always fully charged !
For charging a battery lower than 12.5 Volts, a charger must be used !!!
A CAR'S CHARGING SYSTEM IS DESIGNED TO MAINTAIN YOUR BATTERIES STATE OF CHARGE, NOT TO CHARGE FROM SCRATCH !!! A drained battery (voltage below 11,7 V) wouldn't be fully charged when you did 1000 miles !

For regular 'off-line' usage install a second AGM cyclic battery (they have a weak starting ability, but they can be used cyclically) and power your hi-fi from this battery. There are switch solutions which can manage these batteries (they are being charged too, when you start the engine, not just the starter battery).

So for sum: your battery will be drained, but you should be able to start the engine and you *must* recharge your battery after that !!!

Answer 2

1

Answer 3

Yes, it will, for the reasons outlined by Blazs. I have two batteries in my car (one for just the amplifiers), and I can drain the rear battery in less than 30 minutes, with the engine running (and charging both batteries).

Of course, I have a Kicker ZR1000 amp, bridged into four 12" subs. But, without the engine charging the batteries, the rear battery will have less than 12v in it after 10-12 minutes, when the subs are putting out 154 db's, that is.

If you want to play your stereo when the car isn't being driven, leave the engine running, or hook it up to a battery charger. If you don't do one of those two things, you will be buying batteries AND alternators (though usually, only one goes bad at a time) at least 3-4 times per year.

Answer 4

If you have only the radio or CD player on then the battery drain is very minimal. An hour of this would never drain your battery to the point where the car wouldn't start. If you have all kinds of add ons such as amplifiers and other electronic gear going it will create a heavier load but it should still not drain the battery with only an hours usage.

Answer 5

I don't think so, because back in the days of drive-in movies, after they got rid of the speakers you attached to the windows, you just tuned your radio to a certain channel to get the sound for the film. That's longer than an hour, of course, and nobody's car was running.
Tony C--how does that waste gas? The motor won't be running, and the radio is powered by the electrical system, isn't it?

Answer 6

Dude, you'd be hard-pressed to get better info' than "Blazs (Skoda 120GL)" laid out.

I skimmed that post and actually LEARNED stuff I never hit in 20 years of mobile electronics. Listen to what he's saying (if you're gettin' technical)... that's very good stuff.

His response is my vote, but in the sake of "answers" and not forums, I must respond....


If you are running in accessory-mode, you're pulling juice from your batt. If your sound system is pulling quite a bit, along with anything else like fans, vanity/dome lights, headlights, and other stuff, you can kill your battery MUCH faster than in an hour.

"Blazs (Skoda 120GL)" for the win (FTW) ... great answer.

Answer 7

depending the strenght of charge on your battery prior to the radio working and how good your battery is. take your car to auto zone and have them test the battery and alternator. This should give u 100% knowlege on wether or not you have a good battery or if you had your radio playing to long

Answer 8

If it is a stock system, even upgraded, I dont see any problem with the battery draining. Even if it has a low wattage sub I dont think you would have a problem.

Answer 9

No your just gonna waste gas. Your altenator recharges our battery as long as the engine is on.

Answer 10

Your promblem is not the battery it is the Mustang