Truck jams in your garage

[Musick17]

You guys ever hooked up a car stereo in your garage or something? If so, how'd you do it?

Reason for asking, I'm trying to make a cooler stereo. I ordered some marine grade speakers and amplifier that included a direct iPod hookup. The system runs off of 12v DC. I plan on using a rechargeable battery to run the system on camping/kayaking trips. When the battery goes dead I want an option to plug in and keep partying when available.

So my question. What are your thoughts on converting from 120ac to 12v DC? I want it to charge the batter while plugged in, as well as still continue to play the system. I know I can get power supplies to change from 120 to 12v, with varying amps. But does the amp hours of the battery I get determine the size of the amps needed in the power supply? Does it all depend on the amps drawn by the system total?

I am no electrical engineer. I've taken a construction electrical analysis class so it know ohms law and Kirchhoffs law.. And that's about it. I definitely have the technical know how to do the work myself. I just don't know how to calculate what's going to work.

Let's hear your experiences. Thanks everyone.

 

[black_demon69]

how bout a motorcycle battery and a cheap battery charger and may be a cord with a cigarette lighter connection to plug into cigarette lighter socket.

 

[RonD]

First figure out the power draw of the stereo.

If you have an amp that has 20watts per channel, that will be 40watts, BUT...big but, audio watts are not quite the same as electrical watts, since an amplifier is not as efficient as say a light bulb.
So you need to divide watts by .75 to get real electrical watts.
40/.75 = 53watts
This is also 53watts at FULL VOLUME, wattage used will, of course, drop as the volume does.
And then on the other side wattage will go up if you turn up the bass, takes more energy to produce low frequencies.

To get the amps you divide watts by volts
53w/12v = 4.4 amps

A 12v battery with 30 amp hours would last you approx. 6.5 hours

You would need at least a 5amp power supply to run from 120vAC



And don't be fooled by wattage as far as sound.
If you have 1 watt coming out of a speaker, what wattage would be needed for twice the volume?
2watts?
no
10watts, yes

To double the volume of sound you need to multiply wattage by 10
100watts is twice as loud as 10watts
1,000watts is twice as loud as 100watts

So you see the problem and the game the stereo sellers are playing, lol.
If you were to "upgrade" a 100watt amp to a 300watt amp your ear couldn't detect the change, it would be 2/10ths louder

20watts is very very loud, 100watts would only be 5/10ths louder or 50% louder, barely preceptable to most people

 

[alwaysFlOoReD]

I'm not really knowledgeable but I would guess that you want to have the power system to at least have enough amps to run the system without draining the battery. I would say the amp output of the charging system has to at least equal the amp draw of the music system.
edit; ^^^ better answer.

Richard

 

[tmcalavy]

Get a new deep cycle marine battery and run it off of that...just don't be camping near me in the great outdoors and running that cheet full blast, unless you're out of range of 12 ga. slugs and wearin' body armor.