Slight OT ; Car alternator failing?

B

Billy

Guest
Hi all,

I recently had to buy a battery for my girlfriends car, it failed with the
cold temperatures lately (battery was also nearly 5 years old). In order to
get warranty on the battery i had to go down to the shop to check the
charging system in the car.
The guy hooked up an analyzer did some tests (starting voltage, battery
voltage unloaded, battery voltage loaded,...) and goofed up the first time;
when the analyzer asked to load the battery and run the angine at 2000rpm he
took a while to find the rear window heater and by the time he had the
engine revved up the analyzer sayd he had completed this step.
Result was that the analyzer said that there was a problem in the charging
system, that alternator voltage was to low when it's loaded. Of coarse there
was I said, the car was idling when the analyzer said to run at 2000rpm. The
guy was starting to make an appointment to replace the alternator, but I
convinced him to take the test over.
This time he did it right but then there was another problem, the analyzer
said that there is a to high diode ripple. I couldn't help feeling that I
was being fooled and refused to leave the car behind to replace the
alternator.
Now I would like to check the ripple myself, how much ripple can the battery
take, quite a lot I presume? Am I right that I can check this with a
multimeter set on AC voltage, or should I use a scope?
Btw, test results from the analyzer said that voltage unloaded was 13.65V,
and loaded 13.20V, those are quite normal values I presume?


PS : Sorry if I blabbed along the whole story, for those who hate long
stories, the main question is : what's the maximum ripple a car alternator
may produce?
 
On Thu, 05 Feb 2004 16:31:31 GMT, "Billy" <jurgen. %|NO**SPAM|%
priem@pandora.be> wrote:

Hi all,

I recently had to buy a battery for my girlfriends car, it failed with the
cold temperatures lately (battery was also nearly 5 years old). In order to
get warranty on the battery i had to go down to the shop to check the
charging system in the car.
[snip]
PS : Sorry if I blabbed along the whole story, for those who hate long
stories, the main question is : what's the maximum ripple a car alternator
may produce?
An alternator is an AC machine with 3-phase full-wave rectification,
so the ripple is fairly small, even with a resistive load, barely
noticeable with a battery attached. However, open diodes will show up
as excessive ripple.

Sounds to me like the technician at the shop you chose doesn't know
diddly-squat. Find another place that can test alternators...
preferably one that doesn't *sell* them.

A five-year-before-death battery indicates to me that the charging
system is most likely in good condition. I rarely get more than two
years on a battery here in Arizona... the heat kills them.

(If you are moderately electronically capable: measure the neutral
terminal with an average-reading voltmeter... it should be precisely
1/2 of the battery voltage. *Any* fault will cause this voltage to
deviate from 1/2... I designed a fault-light system for GM eons ago
that does this test.)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
On Thu, 05 Feb 2004 09:45:28 -0700, Jim Thompson
<thegreatone@example.com> wrote:

An alternator is an AC machine with 3-phase full-wave rectification,
I think its a 2-phase, at least mine (you can see some my mods on my
site under electronics at the end ... :)))

-- Regards, SPAJKY ÂŽ
& visit my site @ http://www.spajky.vze.com
"Tualatin OC-ed / BX-Slot1 / inaudible setup!"
E-mail AntiSpam: remove ##
 
On Fri, 06 Feb 2004 02:20:29 +0100, SpajkyŽ <Spajky##@volja.net>
wrote:

On Thu, 05 Feb 2004 09:45:28 -0700, Jim Thompson
thegreatone@example.com> wrote:

An alternator is an AC machine with 3-phase full-wave rectification,

I think its a 2-phase, at least mine (you can see some my mods on my
site under electronics at the end ... :)))

-- Regards, SPAJKY Ž
& visit my site @ http://www.spajky.vze.com
"Tualatin OC-ed / BX-Slot1 / inaudible setup!"
E-mail AntiSpam: remove ##
How many diodes? On this side of the pond we have six diodes, 3-phase
(Y-wound) winding.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
On Fri, 06 Feb 2004 08:21:12 -0700, Jim Thompson
<thegreatone@example.com> wrote:

On Fri, 06 Feb 2004 02:20:29 +0100, SpajkyÂŽ <Spajky##@volja.net
wrote:

On Thu, 05 Feb 2004 09:45:28 -0700, Jim Thompson
thegreatone@example.com> wrote:

An alternator is an AC machine with 3-phase full-wave rectification,

I think its a 2-phase, at least mine (you can see some my mods on my
site under electronics at the end ... :)))

How many diodes? On this side of the pond we have six diodes, 3-phase
(Y-wound) winding.
I have only 2 of them here; IMHO you have much bigger car than mine
needing stronger generator to fill up your much bigger accumulator ...
:)

-- Regards, SPAJKY ÂŽ
& visit my site @ http://www.spajky.vze.com
"Tualatin OC-ed / BX-Slot1 / inaudible setup!"
E-mail AntiSpam: remove ##
 
On Sat, 07 Feb 2004 02:29:53 +0100, SpajkyŽ <Spajky##@volja.net>
wrote:

On Fri, 06 Feb 2004 08:21:12 -0700, Jim Thompson
thegreatone@example.com> wrote:

On Fri, 06 Feb 2004 02:20:29 +0100, SpajkyŽ <Spajky##@volja.net
wrote:

On Thu, 05 Feb 2004 09:45:28 -0700, Jim Thompson
thegreatone@example.com> wrote:

An alternator is an AC machine with 3-phase full-wave rectification,

I think its a 2-phase, at least mine (you can see some my mods on my
site under electronics at the end ... :)))

How many diodes? On this side of the pond we have six diodes, 3-phase
(Y-wound) winding.

I have only 2 of them here; IMHO you have much bigger car than mine
needing stronger generator to fill up your much bigger accumulator ...
:)

[snip]

I have never seen an alternator that didn't have 6 diodes.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
On Fri, 06 Feb 2004 18:59:11 -0700, Jim Thompson
<thegreatone@example.com> wrote:

I have never seen an alternator that didn't have 6 diodes.
IMHO for 3-phase alternator is enough 3 diodes:
coils connected star topology (common is +) & 3 other ends connected
thru diodes to GND (-) ... no need for 6 ones ...

-- Regards, SPAJKY ÂŽ
& visit my site @ http://www.spajky.vze.com
"Tualatin OC-ed / BX-Slot1 / inaudible setup!"
E-mail AntiSpam: remove ##
 
On Sat, 07 Feb 2004 11:25:17 +0100, SpajkyŽ <Spajky##@volja.net>
wrote:

On Fri, 06 Feb 2004 18:59:11 -0700, Jim Thompson
thegreatone@example.com> wrote:

I have never seen an alternator that didn't have 6 diodes.

IMHO for 3-phase alternator is enough 3 diodes:
coils connected star topology (common is +) & 3 other ends connected
thru diodes to GND (-) ... no need for 6 ones ...

[snip]

Do it however you like. You asked a question, I answered. I am an
expert on alternators, check my patents on my website.

You somehow don't like my answers. Ask no more.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
On Sat, 07 Feb 2004 09:15:11 -0700, Jim Thompson
<thegreatone@example.com> wrote:

You asked a question, I answered. I am an
expert on alternators, check my patents on my website.
Ok, I will ... :)

I love to cook with wine. Sometimes I even put it in the food.
:)) , this is agood one ...

-- Regards, SPAJKY ÂŽ
& visit my site @ http://www.spajky.vze.com
"Tualatin OC-ed / BX-Slot1 / inaudible setup!"
E-mail AntiSpam: remove ##
 
"SpajkyŽ" wrote:
IMHO for 3-phase alternator is enough 3 diodes:
coils connected star topology (common is +) & 3 other ends connected
thru diodes to GND (-) ... no need for 6 ones ...
Not really. If you only use three diodes you need heavier field
windings, and the DC output will have more ripple. Using full wave
rectification is cheaper, and gives better performance.

--
We now return you to our normally scheduled programming.

Michael A. Terrell
Central Florida
 

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