battery problem

Pooco

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Sep 14, 2022
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Make
Chevrolet
Model
Impala
Year
2001
Miles
?
Engine
3400 V6
My daughters impala LS with the 3800 battery dies about once a week or every other week, i have installed a known and confirmed very good battery from my truck in it, same problem as her original battery. Car will start fine for days even when she will leave in the morning,then in the afternoon comes and it will need a small jump then be fine for days again. She only drives a short distance each day but always let's the warm up run for a while. What I have noticed is that the alt doesn't (turn on ) right away, after about 10 seconds it'll kick on and start charging. I know the older alternators could have this problem,charge fine while running then die overnight due to bad diodes, but I'm wondering if the newer alternators still could suffer from this type of problem?? My previous 2000 impala LS never had this slow acting alt, it was on as soon as the fired. When I get home today ill do a draw test and see what shows, im suspecting probly not see anything because its somewhat intermittant, what do you guys think about the older and newer alts having similar problems
 

grcauto

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It's a 21 year old car and you're talking as if it's next gen. How are you determining the alternator state?
 

billr

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I don't think the basic design of alternators has ever changed. When alternators (AC generators) first became popular for autos, in the early 1960s, they were essentially the same (but smaller) as the very first AC generators made in the late 1800s. I know they hadn't changed by about 1999, and would not expect they have changed since.
 

grcauto

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I don't think the basic design of alternators has ever changed. When alternators (AC generators) first became popular for autos, in the early 1960s, they were essentially the same (but smaller) as the very first AC generators made in the late 1800s. I know they hadn't changed by about 1999, and would not expect they have changed since.
He may be thinking of the smart charge systems rather than the alternator.
 

billr

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I gotta ask... what is this "smart charge system", how does it relate to the lead-acid SLI battery?
 

nickb2

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I am french, so may have to dissect every thing before I respond, if not,at least I tried.

In a chevrolet impala, no such thing as a smart charging. That came about a bit later. Variable charging started about 8 yrs after this model. Lots of guys throwing alternators at cars and trucks when they saw 12ish voltage on the gauge . Its normal, the pcm decides when it excites the field.

One of the best ways to know if you have a smart charging system, look at the data. If you see SOC in the data, it is a smart charging system.

hint.

So back to Billr question, what does this have to do with a lead acid SLI setup? Nothing.

I took time to read pooco question. And by dissecting this, it smells like a bad current draw, or amp dray or parasitic drain bla bla.

My daughters impala LS with the 3800 battery dies about once a week or every other week, i have installed a known and confirmed very good battery from my truck in it, same problem as her original battery. Car will start fine for days even when she will leave in the morning,then in the afternoon comes and it will need a small jump then be fine for days again. She only drives a short distance each day but always let's the warm up run for a while. What I have noticed is that the alt doesn't (turn on ) right away, after about 10 seconds it'll kick on and start charging. I know the older alternators could have this problem,charge fine while running then die overnight due to bad diodes, but I'm wondering if the newer alternators still could suffer from this type of problem?? My previous 2000 impala LS never had this slow acting alt, it was on as soon as the fired. When I get home today ill do a draw test and see what shows, im suspecting probly not see anything because its somewhat intermittant, what do you guys think about the older and newer alts having similar problems
 

nickb2

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@Pooco, when your daughter drives the car and then it sleep for awhile, is there a whole bunch of young ppl gadgetery inside? smart phone charger, gps etc?

If so, ask her to disconnect everything aftermarket in the car before she goes to do studies and eat and sleep etc. If you dont need to boost her after all that is disconnected, then start pulling fuses if you see anything over 60ma.
 

nickb2

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another hint, if you suspect a bad diode which for some strange reason is your parrasitic drain, that is easy enough, pull the alt fuse. Overnight, what did the battery do, keep volt up or did it go down.

You have to ap[approach this with a sherlock holmes mind.

Often with the young ppl, you just need to understand they dont know everything.

Take the car for a few weeeks, let her drive your truck. If you drive the impala fine and your truck dont start and have to go jump your truck, problem is not truck or car, problem is 18 inches behind the wheel. Trust, I have a 19yr old son. ;)
 

grcauto

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The difference is in the smart charge system it uses the computer to sense battery state and charge load which it uses a PWM signal to control. This allows the battery to be charged at a varying rate rather than on and off.
 

Mobile Dan

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I'm no expert with "smart charging" but I think those systems have some extra sensors mounted on the battery cables to monitor amp draw, and uses that information to determine how much the alt will charge.
 

billr

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Alternators/generators have been controlled with varying field control ever since the relay-style regulators were replaced with electronics; again, back in the 1960's. Computer control? Yes, older regulators are computers, but analog ones, not digital. That PWM technique is just a way to get the analog field power the alt needs more cheaply and with less power loss in the regulator.

Since the power loss in the regulator is fairly small anyway, there is little difference in the efficiency of an alt controlled by pure analog or PWM. I suspect "smart charging" is yet another expensive and trouble-some way to eke out micro-reduction in the use of combustion processes.

So, .back to the original effort. I like the idea of swapping cars for a bit, to see if it is driving pattern, coupled with non-stock equipment, that is the basic cause.
 

grcauto

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That current sensor which is used in the newer smart systems is fairly new. Much later than the 60's
 

billr

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Let's take this to the Lounge. We probably aren't helping the OP with continued discussion of charging system design.
 
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