Battery effects

Think about all the electronics onboard. All require a minimum voltage.
Your dying battery caused things like the ECU to receive less than the 12
volts it likes.
 >> Stay informed about: Battery effects 

On Thu, 23 Dec 2004 13:49:16 -0500, "johninKY" <gflong RemoveThis @nospam.kih.net>
wrote:

 >Think about all the electronics onboard. All require a minimum voltage.
 >Your dying battery caused things like the ECU to receive less than the 12
 >volts it likes.

OK I can understand what you are saying, but when the engine was
running the electronics were running on 14.4v. Overnight, last night
the battery volts dropped to 11.96v which would account for the poor
starting I had this morning. Once the engine was running though, the
voltage was restored, so surely the ECU and everything else were
getting the correct voltage?

Could it have been that ECU was reset whilst the battery was being
changed? If so then I need to do this more often as it has made such
a difference.<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Battery effects 

I experienced the same thing on my 1995 BMW 328i a while ago. Can't really
explain it, but the car was misbehaving badly for a week or so before the
battery died. Replaced battery and everything returned to 'normal'.
Most electronics runs on +5v and/or +12v so I would have expected a running
alternator to provide adequate power... but who knows.

"Tony" <tp DeleteThis @waypoint.vianet.com> wrote in message
news:kj0ms0tune2o6qpmdn9pld747h7lnenn3g@4ax.com...
 >I have a Forester S Turbo. Could a dying battery cause it to run
 > badly? I just had to replace the battery because it wasn't holding
 > it's charge and the car seems to be running a lot smoother since then.
 > I don't understand why this would be because the charging circuit was
 > OK, so whilst driving the voltage would have been normal.
 >
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Battery effects 

On Fri, 24 Dec 2004 08:14:48 +1100, "Jack" <none.RemoveThis@localhost.org> wrote:

 >I experienced the same thing on my 1995 BMW 328i a while ago. Can't really
 >explain it, but the car was misbehaving badly for a week or so before the
 >battery died. Replaced battery and everything returned to 'normal'.
 >Most electronics runs on +5v and/or +12v so I would have expected a running
 >alternator to provide adequate power... but who knows.
 >
 >"Tony" <tp.RemoveThis@waypoint.vianet.com> wrote in message
 >news:kj0ms0tune2o6qpmdn9pld747h7lnenn3g@4ax.com...
  >>I have a Forester S Turbo. Could a dying battery cause it to run
  >> badly? I just had to replace the battery because it wasn't holding
  >> it's charge and the car seems to be running a lot smoother since then.
  >> I don't understand why this would be because the charging circuit was
  >> OK, so whilst driving the voltage would have been normal.
  >>

I had a 99 Chrysler T&C for 3 years. In that time I had two batteries lose a
cell, so that the voltage was down to 11 volts. One of the symptoms was that, on
starting, the speedometer, tachometer and the other gauges wouldn't work. They
still refused to work until I had run the car for a while, stopped the engine
and restarted. So it seems that in some cars adequate voltage must be present on
startup -- the alternator can't make them begin working later even though the
voltage is up to snuff at that time.<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Battery effects 

Tony wrote:
 > On Thu, 23 Dec 2004 13:49:16 -0500, "johninKY" <gflong.TakeThisOut@nospam.kih.net>
 > wrote:
 >
 >
  >>Think about all the electronics onboard. All require a minimum voltage.
  >>Your dying battery caused things like the ECU to receive less than the 12
  >>volts it likes.
 >
 >
 > OK I can understand what you are saying, but when the engine was
 > running the electronics were running on 14.4v. Overnight, last night
 > the battery volts dropped to 11.96v which would account for the poor
 > starting I had this morning. Once the engine was running though, the
 > voltage was restored, so surely the ECU and everything else were
 > getting the correct voltage?
 >
 > Could it have been that ECU was reset whilst the battery was being
 > changed? If so then I need to do this more often as it has made such
 > a difference.
 >
 >
 >
Sound like you know something about auto electrics. I wouldn't
consider high load on alt as even if alt could put out 100A that is
about 2HP not enough to make a noticeable impact.

The 11.9V is a concern. A fully charged 12V LA battery should read at
rest 12.7V. I would check and see what kind of load there is on the
battery when engine is not running. At the sub 12V level a large
percentage of capacity is gone. Why, is the first thing I would be
checking on. There could be a relationship between what is
discharging the battery and the poor performance you first mentioned.

Mickey<!-- ~MESSAGE_AFTER~ -->
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On Fri, 24 Dec 2004 08:21:47 -0800, Mickey <mickey RemoveThis @webster.com> wrote:


 >
 >The 11.9V is a concern. A fully charged 12V LA battery should read at
 >rest 12.7V. I would check and see what kind of load there is on the
 >battery when engine is not running. At the sub 12V level a large
 >percentage of capacity is gone. Why, is the first thing I would be
 >checking on. There could be a relationship between what is
 >discharging the battery and the poor performance you first mentioned.
 >
 >Mickey

There is negligible load on the battery when everything is switched
off.

Using a Specific Gravity tester on the electrolyte, the battery was
showing an *almost* full charge on all cells after a short run. The
voltage was 14.7 when the engine was running and everything was
switched on so I know it wasn't a charging problem. The high current
discharge of the battery was OK and it tested at about 12.7v as you
suggest but it was loosing charge overnight, down to 11.9v over 12
hours.

I have already replaced the battery and the car runs a lot better now.

My original question was why this would make the car run so much
better. Logic says it can't be the voltage drop from the apparently
faulty battery because as long as the engine will start and is running
there is no voltage drop.

Merry Christmas to all<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Battery effects