Jmai22

I'm trying to figure out how long i can leave my engine off and watch a movie using my optima yellow top battery. they are rated at 120 minutes drawing 25 amps. and 60 minutes drawing 50 amps. How many amps would you say my system is drawing if i have a RF 400a4 amp and a JBL 1200.1 amp, Sony x-over, and 1 farad RF digital cap??

pcmw

You can find an inductive amp meter. Or you could use a data logging multimeter to figure it out.

MW

APLUS

Not an expert in car audio but since I did take electronics communication for three years I might be able to steer you in the right direction. First you really can't tell how much current your drawing without knowing how much resistance there is (the wires) You need to know the gauge of the wires and the connectors will play a part also, whetehr there gold plated or regular. To figure all this out accuratly you would be better off taking it to a car shop and having them measure it with a multi meter. Anything else is just guessing.

Jmai22

dam didn't know it was that hard. i got a few replies from a 1 other forum and they suggested me to mount a digital volt meter. anyone know if a good digiital volt meter for under 30 bucks?? also whats a safe voltage i should start my engine before its too late?? would 11 volts be too low to be able to start my engine. that's what i was recomended

BananaGS

There is NO good multi meter under $30 that can measure "current" up to 100A or more.

Now, a cheap volt meter at Radio shack can tell you the VOLTAGE (not current) at the battery.

All you do is:
-measure the voltage at the battery at the begining of of test.
-Measure it again every 10 min of playing.

When your voltage drop down to 10.5V, that is too low. You are hitting your bottom end. Don't quote me on the 10.5V number, just my guessing.

Thus, you don't need an AMP meter to figure out when you should stop playing.

Also, depend on the type of the music (lot of bass or not) and the playing volume, the drawing current of your AMP is varied in every notes of the music.

Your study on "how long" is pretty much useless when you pop in a different music track anyway.

if the voltage goes low, Turn off your music, for a couple of minutes, you should be able to start your car, that is the beauty of deep cycle battery. hee hee. Notes, this is how you destroy a battery anyway.

Percy

Inductive clamp is the only way I know of. Most systems will run over 30 amps+ if they're over 200 watts, at full rated power. See if anyone that you know has a Fluke inductive clamp...or a current clamp.

Percy

Jmai22

how about those round meters that people put in there dashboard that reads the current voltage. would that give me accurate voltage readouts? within .5 +-

pcmw

Jmai,

There are several volt meters that are cheap. Even several digital models that would look really nice. However, volt meters will not tell you the whole story. If your issue is, can I start my car, then you are fine with the volt meter.

MW

Jmai22

is there something higher or better than a volt meter i should be looking for?? i really want to know the status of my car so i don't get stranded. any certain brand names i should invest in?

Percy

Best luck I've had is with Fluke products.

http://www.fluke.com

Percy

Kyle Harty

iTrader: (17)

If I'm not mistaken, most HU's will shut down while you still have enough juice to start the car. Someone correct me if I'm wrong, but there's a decent chance that would save you.

O. L. T.

iTrader: (17)

that fosgate amp is the real drainer. there are a few things you must realize about a car audio amp. They never draw constant current. most idle at 1.5 amps and play at around 12 to 20 amps constant with 35 to 40 amp peaks under severe notes, but only for a second.

with that, measuring the load would be only an estimate based upon the average of the variables. since every time you turn it on, something different would be playing and at a different volume, the sky is the limit on how long it could last, or how quick it could die.

Jmai22

i flipped through there and have used fluke product before. but i couldn't find anything that i can take apart like a standard volt meter so i can disassemble and place it in my dash.

TimDimman

Well, amphr / amp = hr so, your batteries amp-hour divided by the current draw of the system will give you the time you can use it, assuming everything is linear...

Dakota Digital makes some nice meters, but they aren't cheap. Most places will charge you for the sending unit, as well as the meter...

I'd just get an el-cheapo meter, pick an arbitrary V where you know you're vehicle will start, and just don't let it run down below that number.

You know, for the amount of money you'd spend on a meter, you could also purchase a handy "emergency" jump start module.

Tim