alternator whine on stereo upgrade ideas, also battery ideas

["Rod Birch" <HOTROD930@xxxxxxxxxxxxx>]

Paul Wu said he installed a Sony aftermarket head unit in his 325 and now he
has alternator whine over his speakers.  Hmmm.  Do you have the premium
sound package originally in the car, perhaps it has an amplifier somewhere
in the car?  I'm not as familiar with your car as I am with stereos in
general.  Usually alternator whine is caused by either a noisy ground (every
device in your car has a "path" from the device to the battery, and with
BMW's with the alternator at one end of the car and the battery at the other
end you have some really noisy ground paths between the two along the metal
chassis), or a different ground for the radio vs. the amplifier.  In most
stereo installations where I'm mounting an amplifier, I'll actually run the
ground lead for the deck all the way back (16 ga wire is fine) to the
amplifier's same ground location.  They reference the same ground from my
limited understanding.  I never have noise with this.  Troubleshooting noise
is involved, with several possible ways for noise to enter, and a systematic
approach to eliminate sources is the only straight-forward way unless you
guess and get lucky.  I think it's possible that you're sending a much
higher
signal than the factory head unit was into the harness which is then the
"input" for the amplifier, if your car has one, and the amplifier in turn
just boosts all of the music along with the noise (it doesn't know the
difference), and that's what you hear.  Alternator noise usually does
indicate that the alternator is healthy, and sometimes it shows that the
battery is not, since the battery acts as a "filter" for the electrical
system with all of the surges and spikes.

I hope this is helpful, I don't know if your car has an amp or where to look
for one.  Sony's usually have very good filtering on their power supplies
(unless you chopped off the little black box on the power leads), so I don't
think it's just the unit itself, though a faulty unit could theoretically be
at fault.

Also, on the subject of batteries, the best batteries I've seen for any
application are the Stinger "Dry Cell" Power Masters, they literally are a
deep cycle battery and can be completely discharged over 400 times and still
come back to 100% like no other battery.  They discharge current like no
other, and I've got one in my 325's trunk, completely sealed, no gasses,
etc.  It's never even showed a hint of cranking slowly even after listening
to a 600 or so watt system for a few hours.  This battery seems to be less
of a "load" than conventional batteries and "gel cells", and it is the last
battery you should ever buy.  When I sold my last vehicle, I kept this
battery and installed it in my 325, tee hee, and I intend to do the same
next time.  The catch, here it is, is it's $189 retail for the small one,
and $239 for the big one, mounting may require the "sleeve", which is
another $35 or so.  You can check details at their website,
www.stinger-aamp.com .  I'm a dealer, so I can tell you that they have great
products, and I can save list members 10-15% off retail.  (Plug, sorry!)

It's worth checking out.  My rep tells me that they're conservatively rated
for Cold Cranking Amps of 600 and 700 respectively, but they have a much
quicker "recovery" time than conventionals, so they'll give you more
"chances" to start if they're somehow really low, if that makes any sense.

Another long message, I wonder if I'm wearing out my welcome!

- -Rod