On Wed, 31 Oct 2012 22:38:07 -0700, "PrecisionmachinisT"
wrote:


"Existential Angst" wrote in message
...
Toward the end of determining how many "external" car batteries can I put
in parallel with the car battery, without over-loading the alternator??

I know the charging current draw would depend on the degree of discharge
of the batts, so figger 50% discharge.
Or even total discharge, ie, a dead battery.

I figger that if no lights, defrosters, etc are being used, the alternator
could handle two extra batteries, charge-wise.

Have I figgered right?

Is there such a thing as a "current limiter", so that the alternator would
never "short out", from too many loads?
--
EA


Your car alternator is probably capable of generating about 40 amps, which
basically means that it will re-charge a fully dead 40 amp-hour battery in
about one hour.

An average car battery holds ~ 40 ~50 amp-hours, do the math.

After about the trird alternater in a '90 Lumina APV mu mechanic laid down
the law -" When the reading lights get left on and the battery is
dead, charge it up enough to get it here and let it sit on the big
charger for an hour". It seems that after about 1985 factory
alternators are only capable of maintaining the battery, not charging
it from flat.
---

Gerry :-)}
London,Canada

wrote:

After about the third alternater in a '90 Lumina APV mu mechanic
laid down the law -" When the reading lights get left on and the
battery is dead, charge it up enough to get it here and let it sit
on the big charger for an hour". It seems that after about 1985
factory alternators are only capable of maintaining the battery,
not charging it from flat.


Not like the old 83A model on my stepvan. They cut weight every
place they can to try to meet the gas mileage requirements.

On 11/1/2012 8:49 PM, Michael A. Terrell wrote:

wrote:

After about the third alternater in a '90 Lumina APV mu mechanic
laid down the law -" When the reading lights get left on and the
battery is dead, charge it up enough to get it here and let it sit
on the big charger for an hour". It seems that after about 1985
factory alternators are only capable of maintaining the battery,
not charging it from flat.


Not like the old 83A model on my stepvan. They cut weight every
place they can to try to meet the gas mileage requirements.

I don't really think that's it--I just went and looked at replacement
alternators listed for Chevy Lumina -- of 10 or so the amp ratings
ranged from one at 85 to 140 w/ the bulk at 100-105A. I've never had
any problem in any vehicle of recharging a _good_ battery from
discharged condition as long as there wasn't something else wrong (like
a bad regulator, etc.)

Any one vehicle may be built w/ the lower amp-output, of course, but
these days w/ the advent of A/C and all the other electrical accessories
as standard equipment more often than not the alternator is far larger
than on vehicles of yore (say '60s/early '70s and earlier, particularly).

--

dpb wrote:

On 11/1/2012 8:49 PM, Michael A. Terrell wrote:

wrote:

After about the third alternater in a '90 Lumina APV mu mechanic
laid down the law -" When the reading lights get left on and the
battery is dead, charge it up enough to get it here and let it sit
on the big charger for an hour". It seems that after about 1985
factory alternators are only capable of maintaining the battery,
not charging it from flat.


Not like the old 83A model on my stepvan. They cut weight every
place they can to try to meet the gas mileage requirements.

I don't really think that's it--I just went and looked at replacement
alternators listed for Chevy Lumina -- of 10 or so the amp ratings
ranged from one at 85 to 140 w/ the bulk at 100-105A. I've never had
any problem in any vehicle of recharging a _good_ battery from
discharged condition as long as there wasn't something else wrong (like
a bad regulator, etc.)

Any one vehicle may be built w/ the lower amp-output, of course, but
these days w/ the advent of A/C and all the other electrical accessories
as standard equipment more often than not the alternator is far larger
than on vehicles of yore (say '60s/early '70s and earlier, particularly).


But they don't put those bigger models in on basic vehicles with no
AC, do they?

On 11/2/2012 9:46 AM, Michael A. Terrell wrote:
....

But they don't put those bigger models in on basic vehicles with no
AC, do they?

How many vehicles are sold in the US _w/o_ AC these days? Very small
percentage, I'd wager...

But the 85A was the _smallest_ in the list of compatible for the vehicle
class mentioned (out of nearly 20 choices) and there was only one of
them in the first 10 or so of the list (ordered by price) that I
actually paged through that was under 100A. That indicates that
anything under the 80-some A class is pretty limited to me...

I'm sure you can still find 50 and 60A ratings but even they shouldn't
have any problem charging a battery as long as the rest of the system
(and the battery) is in good shape.

IOW, I suspect something else was the underlying culprit in the
preceding comment of killing alternators...

--

On Fri, 02 Nov 2012 08:37:42 -0500, dpb wrote:

On 11/1/2012 8:49 PM, Michael A. Terrell wrote:

wrote:

After about the third alternater in a '90 Lumina APV mu mechanic
laid down the law -" When the reading lights get left on and the
battery is dead, charge it up enough to get it here and let it sit
on the big charger for an hour". It seems that after about 1985
factory alternators are only capable of maintaining the battery,
not charging it from flat.


Not like the old 83A model on my stepvan. They cut weight every
place they can to try to meet the gas mileage requirements.

I don't really think that's it--I just went and looked at replacement
alternators listed for Chevy Lumina -- of 10 or so the amp ratings
ranged from one at 85 to 140 w/ the bulk at 100-105A. I've never had
any problem in any vehicle of recharging a _good_ battery from
discharged condition as long as there wasn't something else wrong (like
a bad regulator, etc.)

Any one vehicle may be built w/ the lower amp-output, of course, but
these days w/ the advent of A/C and all the other electrical accessories
as standard equipment more often than not the alternator is far larger
than on vehicles of yore (say '60s/early '70s and earlier, particularly).
Those 100 to 140 amp units are only good for that kind of output for
a VERY short time - untill they get hot, and die.

wrote:

dpb wrote:

Any one vehicle may be built w/ the lower amp-output, of course, but
these days w/ the advent of A/C and all the other electrical accessories
as standard equipment more often than not the alternator is far larger
than on vehicles of yore (say '60s/early '70s and earlier, particularly).

Those 100 to 140 amp units are only good for that kind of output for
a VERY short time - untill they get hot, and die.


Those old alternators were designed & rated for continuous service.
Today's 100 amp is an old 37 amp with Schottky diodes instead of Silicon
diodes. They have a lower forward drop, and can handle more current in
the same size package.

On Fri, 02 Nov 2012 12:52:01 -0500, dpb wrote:

On 11/2/2012 9:46 AM, Michael A. Terrell wrote:
...

But they don't put those bigger models in on basic vehicles with no
AC, do they?

How many vehicles are sold in the US _w/o_ AC these days? Very small
percentage, I'd wager...

But the 85A was the _smallest_ in the list of compatible for the vehicle
class mentioned (out of nearly 20 choices) and there was only one of
them in the first 10 or so of the list (ordered by price) that I
actually paged through that was under 100A. That indicates that
anything under the 80-some A class is pretty limited to me...

I'm sure you can still find 50 and 60A ratings but even they shouldn't
have any problem charging a battery as long as the rest of the system
(and the battery) is in good shape.

IOW, I suspect something else was the underlying culprit in the
preceding comment of killing alternators...
A bad battery will do it - REAL QUICK.

On Fri, 02 Nov 2012 14:29:28 -0400, wrote:

On Fri, 02 Nov 2012 08:37:42 -0500, dpb wrote:

On 11/1/2012 8:49 PM, Michael A. Terrell wrote:

wrote:

After about the third alternater in a '90 Lumina APV mu mechanic
laid down the law -" When the reading lights get left on and the
battery is dead, charge it up enough to get it here and let it sit
on the big charger for an hour". It seems that after about 1985
factory alternators are only capable of maintaining the battery,
not charging it from flat.


Not like the old 83A model on my stepvan. They cut weight every
place they can to try to meet the gas mileage requirements.

I don't really think that's it--I just went and looked at replacement
alternators listed for Chevy Lumina -- of 10 or so the amp ratings
ranged from one at 85 to 140 w/ the bulk at 100-105A. I've never had
any problem in any vehicle of recharging a _good_ battery from
discharged condition as long as there wasn't something else wrong (like
a bad regulator, etc.)

Any one vehicle may be built w/ the lower amp-output, of course, but
these days w/ the advent of A/C and all the other electrical accessories
as standard equipment more often than not the alternator is far larger
than on vehicles of yore (say '60s/early '70s and earlier, particularly).
Those 100 to 140 amp units are only good for that kind of output for
a VERY short time - untill they get hot, and die.

I worked as a engineering tech with Autolite in the mid 1960. They originated
the commercial automotive alternator for Chrysler. I can honestly tell you that
if an alternator was rated at 60 amps at 14.2 volts it will put that out, for
about the first 5 seconds of testing, thereafter degrading quickly because of
heat and in most cases were not capable of continues max um output for longer
that 1/2 or 1 hour without sever over heating.
--
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To a conservatist's it truly is a free country,
YOU may do whatever they wish. KG
......