playing music while engine is off

**extrarice311** · June 3rd, 2013 11:57 PM

if you have a full sound setup (separates, coxials, subwoofer and amp) is it safe to play and listen to music with the engine off? or will this lead to discharging the battery prematurely. Is it necessary to have the engine running so that you wont drain your battery while playing music.

Any thoughts on this guys?

**jhnkvn** · June 4th, 2013 03:32 AM

Originally Posted by extrarice311

if you have a full sound setup (separates, coxials, subwoofer and amp) is it safe to play and listen to music with the engine off? or will this lead to discharging the battery prematurely. Is it necessary to have the engine running so that you wont drain your battery while playing music.

Any thoughts on this guys?

Depending on your system and battery, I won't recommend playing more than 30 minutes inside a car. If you do it often, you'll lead to premature discharging of your battery as most typical car batteries (ex. Motolite) aren't fans of constant deep discharging. For peace of mind, I suggest just turning your engine ON.. this way, your power source is your alternator and it'll save you the headache of jump-starting your engine if you DID drain your battery.

**the_wildthing** · June 4th, 2013 04:19 AM

Naku nangyari sa akin yan ayaw mag start kasi ang tagal na naka on yung stereo. Napa tulak tuloy si manong security guard. (I was at a paid parking lot at that time.) Factor din siguro medyo luma na yung battery.

Kung stock lang na stereo, no amps, walang masyadong problema kahit 1 hour, at ok pa ang battery mo. (I do this with the minivan all the time, but only low volumes.) Pero pag naka set up, lalo na malakas yung sound, malakas mag drain ng battery.

**1D4LV** · June 4th, 2013 10:20 AM

i think for a fully setup sound system, not recommended. it will eventually drain up your battery. imagine mo na lang kung gano kalakas kumain ng battery ang HU + amp mo....

**mcbry** · June 4th, 2013 11:24 AM

it's not recommended. lakas din kumain ng kuryente yung amp especially if you're playing boom boom sounds. still advisable to turn ON the engine while playing music.

**wezz_zzew** · June 4th, 2013 12:19 PM

You can do that as long as you have the number of Motolite Express Delivery. ^_^

**[archie]** · June 4th, 2013 06:15 PM

yung akin 15mins pwede walang start. don't want to go over that kasi weak na crank sa 15mins. sq basic setup.

**jhnkvn** · June 4th, 2013 10:43 PM

Even if you have amplifiers which output a lot of power doesn't mean your speakers are receiving the exact rated watts everytime. It simply depends on how hard you push your system.

Your power consumption is lower than you think on a basic setup. In normal listening levels, your tweeters and midrange is throwing less than 20W. Bigger displacement drivers such as subwoofers and woofers generally need more watts so they're typically the power-hoggers.

Of course, this is only a generalization. I can have a 8" woofer sounding "big" and being energy efficient just by careful box construction and impedence curve tricks.

**[archie]** · June 5th, 2013 05:23 AM

^kanya kanya lang Yan. since your a numbers guy, maybe provide us with accurate numbers para alam namin limit on playing without starting. Let's say normal listening on a 160 to 200 watt amp. rms of 30watts per ch. running on 3 ch setup. 1sn battery. average time to discharge?

**jhnkvn** · June 6th, 2013 10:38 PM

Originally Posted by [archie]

^kanya kanya lang Yan. since your a numbers guy, maybe provide us with accurate numbers para alam namin limit on playing without starting. Let's say normal listening on a 160 to 200 watt amp. rms of 30watts per ch. running on 3 ch setup. 1sn battery. average time to discharge?

There's no accurate limit because there are too many variables in place. This is especially true if I were to crunch numbers.

In the speaker, there's the factor of speaker impedence. Take my midbass for example: It's nominal at 4ohms but at 69hz rises at 40ohms. And that's just one speaker! What about the others (midrange, tweeters, midbass). There's also a matter of crossovers. The reason why most installers throw out the Focal KRX3 crossovers is because it's poorly designed: there's an ohm load swing in the bass driver around 150hz as such when the system is pushed, the impedance drop is to around .8 ohms stereo causing some amplifiers to go into protection.

In the amplifier, there's the factor of efficiency. This is where amplifier topologies come into play wherein Class A/B amplifiers are less efficient than their Class D counterparts. Not to mention efficiency differs from amplifier to amplifier! Many would also be surprised that our amplifiers are more efficient when near their clipping output and during clipping! Your Class D amplifier might be 90% efficient near its RMS ratings but only 60% efficient at low-listening levels. Remember that this is efficiency... not output. Don't confuse the two.

And lastly, there's the condition of your battery which I won't go into detail because it's standard car maintenance 101.

Let's say your total system wattage eats around 200 watts for your 2-way component set and your 10" subwoofer per hour. 200W is what your amplifier will be throwing out to your speakers.. but let's say it's 70% efficient which is a between 50 and 90. Your amplifier will be demanding 200W/0.7 = 285.71W from your car battery. We then divide this by your usual battery voltage thus 285.71W / 13V = 22A

Because Motolite is stingy in their specification sheet, let's take a look at some "audiophile" batteries such as Stinger's 1SM battery because it's easier to get specifications: Stinger SPV35 (Stinger Electronics | Product Details). Note that there's different ampere/hour ratings depending on rate of discharge (that's another variable) but assuming the battery's fresh, that battery has a 1/2 hour rate of 43.75A or 21.9 ampere/hours, what this means is that your battery will provide 44 amperes of power for 30minutes before dropping down to <11V. So assuming system consumption is at a minimum (ex. no flashing of lights, etc.), your battery can provide power for approximately an hour before discharge.

I hope the math does not confuse anybody. Even I hate doing them

At the end of the day, it really differs by how much you're pushing your volume. Like I said, you're not actually doing 200W or 300W on an everyday basis. Scientifically, decibels is a bad measurement because speakers' sensitivity differs from driver to driver (ex. horns can be rated at 100dB versus your conventional 85dB efficient speaker) but since it's not like people know their power consumption on a rated basis, I still go for "volume". I simply hope people aren't deaf and that their 95dB isn't "normal conversational level" :D