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#5677 - 11/24/04 05:08 PM Re: Car Amplifier
painttoad Offline
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Registered: 10/25/04
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Loc: peoria il
not more "electricity" so to speak
you'll still not have more than 12 volts but the reserve will be there

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#5678 - 11/24/04 05:16 PM Re: Car Amplifier
gonk Offline
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Registered: 03/21/01
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Loc: Memphis, TN USA
Found this at Optima's site regarding battery runtime and "amp hours":

Quote:
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.)
The D34/78 is rated for 55 amp hours and 120 reserve minutes, so one battery will yield 2.75A steadily for 20 hours (55 amp hours divided by 20) before reaching 10.5V and being classified as "fully discharged." It will carry a 25 amp load for two hours before needing to be recharged.
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#5679 - 11/24/04 05:20 PM Re: Car Amplifier
gonk Offline
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Loc: Memphis, TN USA
It's been a while since I messed with electrical circuits, but they are similar enough to pumps that I can keep up somewhat... Adding batteries in parallel would provide more amps at the same voltage, right?
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#5680 - 11/24/04 05:32 PM Re: Car Amplifier
painttoad Offline
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Loc: peoria il
i think you are right gonk(i'm not gonna pretend to "know something" if i'm not sure)
but i'm doing it all for reserve in my truck i have an 160 amp alternator that cannot power the truck and stereo so, basically they provide the ooooooommmph for a peak (reserve)i was sold on my amps because the are "unregulated" whereas if you can put more in you get more out (to a limit of course)

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#5681 - 11/24/04 05:40 PM Re: Car Amplifier
painttoad Offline
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Registered: 10/25/04
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Loc: peoria il
it's amazing gonk, i'm talking about 160 amps here and you are on another thread talking about 15 amps!
how can there be such a difference between the home and car power requirements.
this is a good question if somebody really knows(and don't say cabin gain 'cuz if there is such a thing then why do i have to have 4 times as much in my truck compared to home in something 1/20 of the size)???

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#5682 - 11/24/04 05:46 PM Re: Car Amplifier
gonk Offline
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Registered: 03/21/01
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Loc: Memphis, TN USA
In the case that theendofday is considering, there is not an alternator available to provide that baseline 160amp flow (unless he runs power in from his car and leaves the engine running), so he would be using the batteries in parallel to produce all of the current for the system. If we take a trio of batteries in parallel, that would be either an 8.25 amp load for 20 hours (which wouldn't offer much) or up to 75 amps for only two hours. For brief demos in a store, that would probably be pretty effective - running at a very low level for most of the day with brief spikes up to a very high level would probably not drain the batteries until near the end of the day. For use in a 5.1 channel home theater, it may be fine for prolonged two-channel listening or watching TV at moderate volumes, but you may also find yourself stopping at the end of the first disc of the extended edition of Return of the King to recharge batteries before continuing with the second disc.
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#5683 - 11/24/04 05:47 PM Re: Car Amplifier
painttoad Offline
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Registered: 10/25/04
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Loc: peoria il
i spoke too soon,i went out to have a smoke and started thinkin' DC and with the wattage and current ratings out of my home amp it kinda collaborates with my car amps

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#5684 - 11/24/04 05:52 PM Re: Car Amplifier
gonk Offline
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Registered: 03/21/01
Posts: 14054
Loc: Memphis, TN USA
You're looking at amps at two different voltages. We're looking at 15A when it comes in at 120V, but with home theater equipment we don't really track how many amps may be zipping around downstream of the transformer or really even what voltage it's at (although the equipment's designers certainly do). In a car, you don't have 120V, you have 12V, so to achieve the same power (watts) you have to increase the current (amps) by a factor of 10.

Think about it this way - your 160A alternator is operating at 12V, while the outlet behind your entertainment center is connected to a 15A circuit breaker and is operating at 120V. The two are capable of providing roughly the same wattage - 1800W for the outlet inside, or 1920W in the car.
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#5685 - 11/24/04 06:10 PM Re: Car Amplifier
painttoad Offline
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Loc: peoria il
ok that helps!

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#5686 - 11/24/04 06:20 PM Re: Car Amplifier
JT Clark Offline
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Registered: 10/25/02
Posts: 466
Loc: IL
gonk, good explanations. This topic has really gotten going here. eek

Do you guys seriously think he should use the batteries? How is he going to recharge them? I thought this setup was supposed to be an HT setup. Meaning he should be able to just plug it in and only have to turn it on and off, basically. Besides the tweaking of the settings he'll need to do I mean.

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