I was reminded about the volt meter built into the passport 8500 so I turned mine on a couple of weeks ago.

Since then (and since I got my sub) I have noticed that when the car is running I get some .1 sometime even .2 variations on the voltage reading. Now, I realize the meter might very well not be able to update itself often enough or whatever, but it SEEEEMMS like it MIGHT be related to when the sub hits. In my other cars the 8500 seems pretty rock steady with it's display. This is not the issue that concerns me most though.

The other thing I have noticed is that at stoplights (I am stopped, the car is running, but not revving) it drops from the 14.5 range to the 12.4 range. When I start revving again (the light turns green) it doesn't always jump back up right away.

Note: I don't drive the car VERY often and as a result it may sit for a week or more sometimes. I will often have to throw my battery charger on it to start it as the battery just doesn't have enough juice to get the starter to turn over.

I don't have a HUGE system, but I do have one. I have somewhere around 450 watts total out of my amp. More details on the system (including ALL part numbers) are in the link in my sig.

I'd rather not just go out and drop $$$ for a new battery if I don't have to. Am I just being too paranoid?

 

this is all normal for me. except that i've rarely seen anything above 13.9 for my S.

as i understand it, the alternator runs when needed.... so, at a stoplight and such, the requirements are low and the alternator will kick off (just like an AC compressor), and your voltage will dip down to battery level. as the power requirements of the car go up, the alternator will kick back in and make up for it.


and yes -- my volt meter on the 8500 dances all over the place on heavy bass.... i've had it jump down over a volt below normal when running at times... from 13.9 to 12.5 or so and bounce back up after the bass note. (this is happening in fractions of a second)
just think of it as your own mini rave...

 

Your battery should last well over a week without starting the car. My S sat for 2 to 3 (maybe more) weeks at a time in the winter without starting and it cranked over just fine even when it was cold out. Of course the battery was pretty new. I've had all kinds of cars sitting at the airport for a couple of weeks straight and not had a problem. The only times I did was when the battery was getting rather creaky.

I don't think that the voltage swings you see with the bass are abnormal but I do think that your car should be able to sit for over a week without killing the battery.

Probably should get a new one for next winter if you drive it in the winter.

 

It also depends how sensitive your voltmeter is. Some voltmeters (like my craftsman, take a reading so often (once every millisecond or something like that) and as a result, it will NEVER show you the same number, nor will it stay on the same number.

.1 or .2 is nothing. Alternator output varies, so no worries. Its when your volts start to dip by the full volts is when you have to worry. Remember the m3 I did? (Tarantula 1600.2, Tarantula 500.4, W7x2, Perfects 6.1x2) When the system was on FULL blast, the voltage would dip from 14.3 to 11.2 THAT is some serious draw!

 

oh -- yeah, i missed the not being able to start thing... doh.

how long are we talking? i know you store yours on occassion Pete...


and if it isn't a long period of time (say several weeks) -- then yeah, you could be seeing the early death of the battery.

but all the other stuff? that's pretty normal.

 

Cool. Thanks guys. I now feel like the poster child for idiot lights.


I don't drive the car in the winter, so no worries there. I remove the battery and put it on a tender while in storage.

The battery recharging issue might be just the fact that I only recently pulled it out of storage and started driving it again, so perhaps the battery doesn't always get a chance to fully recharge while driving. (Lots of small trips on the weekends sometimes.)

 

*nods*

no problem Pete.... better safe than sorry.

 

my Greddy voltmeter also shows fluctuations when the system is on.
even with system off when i pull up to a light or put the a/c on their is a large draw.

 

from my past experiences, a good way to tell a weak battery is checking the voltage right when you crank the motor. if it dips below, iirc, 10 or 9 volts, its time to get a new one.

someone correct me if i am wrong on the voltage dip at crankup.