Honda Car Forum

Ricky Spartacus wrote:
> "Matthew Russotto" <russotto@grace.speakeasy.net> wrote
> > Kaz Kylheku <kkylheku@gmail.com> wrote:
>
> > >You do understand that when you push-start a car, that causes the
> > >alternator to spin, which generates electricity, right?
>
> > You seem to be a little behind. If your battery is actually dead, the
> > alternator doesn't generate electricity when it spins.
>
> For one thing, if an alternator needs power to its field
> coil in order to work then how did the car run without
> the battery?

Automotive alternators can self-excite. Once they are running, some of
their own generated current is used to power the field. So if you
disconnect the battery at that point, the engine keeps running. I don't
think that's the case in every alternator design, certainly not
historically.

In article <dt72v002d6@news4.newsguy.com>,
Nate Nagel <njnagel@flycast.net> wrote:

> Ricky Spartacus wrote:
> > "Matthew Russotto" <russotto@grace.speakeasy.net> wrote
> >
> >>Kaz Kylheku <kkylheku@gmail.com> wrote:
> >
> >
> >>>You do understand that when you push-start a car, that causes the
> >>>alternator to spin, which generates electricity, right?
> >
> >
> >>You seem to be a little behind. If your battery is actually dead, the
> >>alternator doesn't generate electricity when it spins.
> >
> >
> > For one thing, if an alternator needs power to its field
> > coil in order to work then how did the car run without
> > the battery?
> >
>
> you probably can't push start an alternator car completely without a
> battery, unless there is enough residual magnetism in the field coils to
> allow the alternator to bootstrap itself.

At which point, the diodes will probably go up in smoke, leaving you
with a dead (if present) battery, *AND* a dead alternator.

Running an alternator no-load/micro-load is a great method of letting
the magic moke out of the diodes.

--
Don Bruder - dakidd@sonic.net - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more info

Kaz Kylheku wrote:
>
> Ricky Spartacus wrote:
> > "Matthew Russotto" <russotto@grace.speakeasy.net> wrote
> > > Kaz Kylheku <kkylheku@gmail.com> wrote:
> >
> > > >You do understand that when you push-start a car, that causes the
> > > >alternator to spin, which generates electricity, right?
> >
> > > You seem to be a little behind. If your battery is actually dead, the
> > > alternator doesn't generate electricity when it spins.
> >
> > For one thing, if an alternator needs power to its field
> > coil in order to work then how did the car run without
> > the battery?
>
> Automotive alternators can self-excite. Once they are running, some of
> their own generated current is used to power the field. So if you
> disconnect the battery at that point, the engine keeps running. I don't
> think that's the case in every alternator design, certainly not
> historically.

You are 'very' far out of date and way off on this one. GM made a 'one
wire' alternator that will self excite if the rpm get up high enough.
Once running, some alternators can feed off their own power output, but
this isn't 'self excite' at all.

On 'modern' vehicles, if you disconnect the battery, the open ended
alternator surge 'will' destroy the computer, ignition module, stereo if
turned on and any other electronic part active before the alternator
itself smokes out.

That just plain don't work no more, same as push starting a dead or
really low battery car. The battery has to have over 10 volts in it to
turn on the electronics and still have enough to turn the fuel pump on.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

In article <1140247829.116443.74670@z14g2000cwz.googlegroups. com>,
Kaz Kylheku <kkylheku@gmail.com> wrote:
>Matthew Russotto wrote:
>> In article <1140207201.324855.20210@f14g2000cwb.googlegroups. com>,
>> Kaz Kylheku <kkylheku@gmail.com> wrote:
>> >
>> >Yes, they need a field current. But that has nothing to do with the car
>> >being modern, does it? Are alternators considered modern?
>>
>> Yes. Before there were alternators, there were generators. These had
>> permanent magnets and did not require a field current to start.
>
>"Alternator" is another name for "AC generator".

When referring to the parts in automotive applications, the term
"generator" always refers to the fixed-magnet device using a
mechanical commutator, and "alternator" to the one with field coils
and rectifying diodes.
--
There's no such thing as a free lunch, but certain accounting practices can
result in a fully-depreciated one.

In article <1140261444.092350.247300@f14g2000cwb.googlegroups .com>,
Ricky Spartacus <rspartacus@gmail.com> wrote:
>"Matthew Russotto" <russotto@grace.speakeasy.net> wrote
>> Kaz Kylheku <kkylheku@gmail.com> wrote:
>
>> >You do understand that when you push-start a car, that causes the
>> >alternator to spin, which generates electricity, right?
>
>> You seem to be a little behind. If your battery is actually dead, the
>> alternator doesn't generate electricity when it spins.
>
>For one thing, if an alternator needs power to its field
>coil in order to work then how did the car run without
>the battery?

If you start a car and disconnect the battery, it will remain running
off the alternator. Once it is running the alternator does not need
_external_ power to its field coil. However, note that the battery
does provide some voltage regulation to the whole system, so
electrical devices may behave erratically if you don't have the
battery in there. (seen it myself)
--
There's no such thing as a free lunch, but certain accounting practices can
result in a fully-depreciated one.

In article <43f740c5$0$58092$742ec2ed@news.sonic.net>,
Don Bruder <dakidd@sonic.net> wrote:
>In article <dt72v002d6@news4.newsguy.com>,
> Nate Nagel <njnagel@flycast.net> wrote:
>>
>> you probably can't push start an alternator car completely without a
>> battery, unless there is enough residual magnetism in the field coils to
>> allow the alternator to bootstrap itself.
>
>At which point, the diodes will probably go up in smoke, leaving you
>with a dead (if present) battery, *AND* a dead alternator.
>
>Running an alternator no-load/micro-load is a great method of letting
>the magic moke out of the diodes.

The other electrical accessories are enough to keep the diodes from
going up in smoke. Been there, done that, when a battery wire terminal
corroded all the way through.
--
There's no such thing as a free lunch, but certain accounting practices can
result in a fully-depreciated one.

In article <43F74351.C8F17DC8@sympatico.ca>,
Mike Romain <romainm@sympatico.ca> wrote:
>
>On 'modern' vehicles, if you disconnect the battery, the open ended
>alternator surge 'will' destroy the computer, ignition module, stereo if
>turned on and any other electronic part active before the alternator
>itself smokes out.

No, it won't. I've had a battery terminal corrode through and nothing
of the sort happened. Granted, that was not a completely modern car
(electronic ignition, but carbeurated). I've also run a modern car
with a battery which was damaged and not taking a charge; while the
gauges acted erratically and the car idled badly, it was not instantly
damaged.
--
There's no such thing as a free lunch, but certain accounting practices can
result in a fully-depreciated one.

I have seen a mess of newer ones killed like mentioned....

Carb engines are different animals.

Mike

Matthew Russotto wrote:
>
> In article <43F74351.C8F17DC8@sympatico.ca>,
> Mike Romain <romainm@sympatico.ca> wrote:
> >
> >On 'modern' vehicles, if you disconnect the battery, the open ended
> >alternator surge 'will' destroy the computer, ignition module, stereo if
> >turned on and any other electronic part active before the alternator
> >itself smokes out.
>
> No, it won't. I've had a battery terminal corrode through and nothing
> of the sort happened. Granted, that was not a completely modern car
> (electronic ignition, but carbeurated). I've also run a modern car
> with a battery which was damaged and not taking a charge; while the
> gauges acted erratically and the car idled badly, it was not instantly
> damaged.
> --
> There's no such thing as a free lunch, but certain accounting practices can
> result in a fully-depreciated one.

In article <k7mdnSzcvb_wC2renZ2dnUVZ_tidnZ2d@speakeasy.net> ,
russotto@grace.speakeasy.net (Matthew Russotto) wrote:

> In article <43f740c5$0$58092$742ec2ed@news.sonic.net>,
> Don Bruder <dakidd@sonic.net> wrote:
> >In article <dt72v002d6@news4.newsguy.com>,
> > Nate Nagel <njnagel@flycast.net> wrote:
> >>
> >> you probably can't push start an alternator car completely without a
> >> battery, unless there is enough residual magnetism in the field coils to
> >> allow the alternator to bootstrap itself.
> >
> >At which point, the diodes will probably go up in smoke, leaving you
> >with a dead (if present) battery, *AND* a dead alternator.
> >
> >Running an alternator no-load/micro-load is a great method of letting
> >the magic moke out of the diodes.
>
> The other electrical accessories are enough to keep the diodes from
> going up in smoke. Been there, done that, when a battery wire terminal
> corroded all the way through.

Tell that to the alternator that died with a very visible (and
aromatic...) cloud of smoke, a pop that sounded about like a .22 going
off, and a "bacon frying" sound that was easily audible over the normal
engine noise when, instead of just twisting the ground cable on the
battery post as I was trying to do, I managed to lift it off the post
and fumble it instead.

There might have been ten seconds, if that long, of "no battery
connection" involved as I retrieved the cable end, got it lined up, and
stuck it back on the post, but by the time that was accomplished, the
smell of burnt electronics was overwhelming. Testing it on the local
Kragen's machine an hour or so later showed a bad diode trio, and the
pre-rebuild inspection later on revealed that one of them had been
reduced to a lump of char, another was split open, and the third was
just plain GONE - As in no sign of it to be seen other than a scorch
mark in the empty spot where it should have been.

(Yeah, I know... I shouldn't have been dicking with it with the engine
running - We've all got 20-20 hindsight.)

--
Don Bruder - dakidd@sonic.net - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more info

"Mike Romain" <romainm@sympatico.ca> wrote

> I have seen a mess of newer ones killed like mentioned....
> Carb engines are different animals.

Years ago, my 260K miles, 1988 Honda Accord fuel injection
battery cable was cut by the fireman who was at the scene of the
accident. The car idled smoothly for maybe 10 minutes until I'd
shut it off. I still drive it today.

I believe there is a button you can push on these alternator to
go full field. Otherwise, they're self regulated. Last I'd checked,
the voltage never exceeded 15V when idling with the battery
cable unplugged.