Run an mp3 player on a car battery?

How big is the manufactures battery (yes there should a be an amp/hour rating for the battery?) How long does that battery last now when played continuously?

 

Hi VersionThirst.
Is this a torture thing, one song for a year, wow i hope you pick one you like, the bigger the amp hour the longer it will last, use a regulator circuit to power the MP3 player, one song for a year, wont you get bored ?

 

The battery rating is amp hours, not amps per hour. A rating of 1 amp hour means that the battery can provide 1 amp for 1 hour or 1/10th A for 10 hours, or 2 amps for 1/2hour.

If you expect the music to be heard by someone walking or bicycling by, you will need amplfication, and this will take more power than the MP3 player itself. I would expect about 1 Watt minimum. To run 1 W continuoulsy for a year from a 12V battery would require (at 100% efficiency) about 730 A hours. That is a lot of battery!

Also, the amp hour rating is at a specific current, much higher than you would be drawing. You will not get the same capacity drawing a fraction of an amp.

I don't think this is practcal, and if do want to continue, I hope your budget is large.

Bob

 

I could also see someone ripping off your batteries. They are not cheap and people will steal just about anything these days. Do you really want to spend that kind of money on something you have no control over?

Looks like you have some decisions to make.

 

with bob's 1W example for 570 hours, you would need [email protected]% efficiency. One car battery should handle that. But you will never get 100% efficiency out of a circuit. I think a typical car battery has a 70AH rating. I don't know how efficiency is calculated, but 70% of 70AH is 52AH. So it seems to me at least this is now plausible.

absolutely

 

Using an inverter will waste battery power, you cant just connect a speaker, you need to amplify it through a modest amplifier, again this will draw power, and not the same as the mp3, unless its a 12 volt car type amp, you need to drop the voltage from the battery's to a voltage the mp3 player can work at, a regulator circuit would do.

The time it lasts depends on the amps power reqirments, and the mp3 power requirments, combined sum in current to work out the total draw of power on the battery's.

If you build a regulator circuit for the mp3, and source a suitable amp you might be able to put something together, powering the mp3 is the easy and not power demanding bit, the amp is another story, more power more current less battery time, how loud will depend on the amp you use.

 

I think I would look at powered computer speakers. These should be good enough and they come prepackaged with an amplifier. You just need supply the DC power.

 

Top idea, i use them on a tuner from the mains, but despence with the mains, as its a power supply, 12 volts, and make a lead up for the battery's, inline fuse etc.

 

Car batteries will sulphate if left discharged. I suggest scaling for one month and re-charging each week.

It should be simple to turn off the device when it is dark, so saving power.

 

just a note on the night thing. as we are all aware sunrise and sunset change. why not put a "light detector" on it instead and that will be your on/off switch.
this won't work if you are putting it near a street light however

 

Donkey makes a great point, depending on where its sitting.

Duke: On the sulphate thing would a deep cycle marine battery be any different in this case? Maybe our adventurer would have better luck with something along those lines... though I would imagine the specs of the battery would be a bit different.

 

I do not know too much about batteries but starter batteries are intended to provide a large starting current and then be recharged immediately. Deep cycle batteries are not intended to provide high currents so may be better in this application.

 

Agree with duke37, you want a deep cycle battery for this purpose.

Bob