How long can you listen to the stereo with the car off?

[Mazdaspeed96743]

Hi guys. I have a 1994 Mazda MX-3 which is a 4-cylinder and I was wondering how long can you listen to the car's stereo with the car off and not having to worry about if the car is going to start up again. I only have a Clarion head unit running 55watts to the 4 speakers... Front door speakers are upgraded with Eclipse speaker with tweeter and I am running two 8 inch subs in the truck powered by the Head Unit. So the fader is set to "(Rear8)" so that you can hear the bass in the rear and some faint music comming from the front speakers. I was thinking of running a cross over for the front speakers so you can hear the song better than just boom BOOOM BOOOOM! but i'll do that later. So anyways, My car battery is stock and its pretty old and haven't have been changed yet so yeah.. Can some experienced person tell me how long can you listen to the stereo with the car off?

[nope-mx3]

I say until the battery runs flat
(or actually right before)

nope-mx3

[Typhoonk]

Check this out:

"Battery Storage Capacity Ratings

Two standard ratings are used to measure a battery's storage capacity.

Amp Hours

The Amp Hour rating tells you how much amperage is available when discharged evenly over a 20 hour period. The amp hour rating is cumulative, so in order to know how many constant amps the battery will output for 20 hours, you have to divide the amp hour rating by 20. Example: If a battery has an amp hour rating of 75, dividing by 20 = 3.75. Such a battery can carry a 3.75 amp load for 20 hours before dropping to 10.5 volts. (10.5 volts is the fully discharged level, at which point the battery needs to be recharged.) A battery with an amp hour rating of 55 will carry a 2.75 amp load for 20 hours before dropping to 10.5 volts.

Reserve Minutes

Reserve minutes is the number of minutes a battery will carry a 25 amp load before dropping to 10.5 volts. (10.5 volts is the fully discharged level, at which point the battery needs to be recharged.)"


found @ -> > http://www.1st-optima-batteries.com/amp_hours.asp

[Mazdaspeed96743]

Check this out:

"Battery Storage Capacity Ratings

Two standard ratings are used to measure a battery's storage capacity.

Amp Hours

The Amp Hour rating tells you how much amperage is available when discharged evenly over a 20 hour period. The amp hour rating is cumulative, so in order to know how many constant amps the battery will output for 20 hours, you have to divide the amp hour rating by 20. Example: If a battery has an amp hour rating of 75, dividing by 20 = 3.75. Such a battery can carry a 3.75 amp load for 20 hours before dropping to 10.5 volts. (10.5 volts is the fully discharged level, at which point the battery needs to be recharged.) A battery with an amp hour rating of 55 will carry a 2.75 amp load for 20 hours before dropping to 10.5 volts.

Reserve Minutes

Reserve minutes is the number of minutes a battery will carry a 25 amp load before dropping to 10.5 volts. (10.5 volts is the fully discharged level, at which point the battery needs to be recharged.)"


found @ -> > http://www.1st-optima-batteries.com/amp_hours.asp

Oh ic, So I can run my stereo on with the car off for 95minutes max.

[Mazdaspeed96743]

I say until the battery runs flat
(or actually right before)

nope-mx3

[Nd4SpdSe]

Considering that I have 2 optima red tops in parallel, i've been guestimating betweek 4-6 hours with the CarPC running...haven't tested that tho, pretty hard too.

With the basic battery that came with the car, I had the CarPC and the stereo running for about 2 hours (watching a movie) before the AC inverter started to freak out from low battery (10.4v). Running 2 in parallel, that should be an easy 4 hours.

[Mazdaspeed96743]

Thank you so much Nd4SpdSe.. You said it all!

[MX-SLICK]

If you just have a head unit and no amps you can have it on for probably 1-2 hours before i would worry about the battery getting run down. Probably even longer if the volume is not cranked. Dont bother with a crosss over, you are only getting about 15 watts to each speaker off the head unit (if that)...i know it says 50x4 but just like every other head unit that is an outright lie. Most headunits are rated between 10-20 watts RMS x 4 high distortion. Get an amp for those 8" subs, it will sound a million times better.

[Mazdaspeed96743]

Wow okay thanks again. Yeah usually I crank the volume up to level 25 out of volume 33 max. And thanks about the amp thing. I think I might buy my friends crappy 300watt VR2 amp for only $25.00 and power it with that

[Nd4SpdSe]

Well, to see Star Wars Episode 3 Thursday night and i forgot to turn off my CarPC. 3 hours later, after the movie, I get into the car and hear the cpu fan of the computer. I turn the key and the car started without hesitation....one of the reasons why i decided to go dual-paralled batteries instead of seperating them with an isolator

Just a bit of history, as i've said, when I had the basic batter that came with the car, I was getting over 2 hours, however, as time went on, in about a years period, my battery life went down to less than 30min before getting the low voltage warning. I couldn't even watch a full Simpsons episode (on antenna from 6:00-6:30, I used to goto the movies weekly with some friends, but i would leave right from work and get there early, cause home was completely in the opposite direction) before the inverter would shut off from low power

[Mazdaspeed96743]

Aww, you lost 30minutes of battery life?. damn that sucks gee well thank you so much for letting me know

[Gro Harlem]

i got a redtop....i never had any ill effects if i ran my stereo w/the car off for a few hours. car started right back up like nothing happened!

If you have a normal non-optima I would be more careful. Just leaving the friggin domelight on overnight can kill a normal battery...happened to my 323 this winter :grr:

[Nd4SpdSe]

Aww, you lost 30minutes of battery life?. damn that sucks gee well thank you so much for letting me know

technically I lost an hour and a half of battery life, I went from 2 hours to 30min on the basic battery

If you have a normal non-optima I would be more careful. Just leaving the friggin domelight on overnight can kill a normal battery...happened to my 323 this winter :grr:

The 626 a few weeks ago, I left the headlights on when i went to work. I came out 3 hours later to get lunch and the battery was completely dead, no power in any way (yet, I accidentally left the CarPC running in the Mx-3 for 3 hours while at the theaters watching Star Wars last week, and the car started without hesitation or a blip from the CarPC, gotta love dual Optima ) My parents/sister have been known to kill the battery by leaving the dome light on in the 626 overnight as well.

[Mazdaspeed96743]

Me gotta switch to optima

[Legato626]

Well my old battery my 15in 200watt 6 speaker 5volt eclipse sound system would DIE in like 1 or 2..... Pissed me off when i am working at my shop and my car wont start i have to push start the mother....

After getting up and getting ready for work and my miata has a flat tire so i jacked up the miata got the tire off and got in my mx-3 turned the key....click...ok again turned the key.......click.......well s---. So i said screw it spent 130 bucks got a red top and i never will die again. Siting in my shop for 9 hours installing my new front end i go and start my car. Feels good to know the best 130 bucks i ever spent on my car was a damn battery.