# Slow Alternator



## Robby (Mar 1, 2013)

So far, your description is that of a normal, computer controlled alternator.
Members were seeing this when the Cruze was introduced here in 2011 and we have noted this on each subsequent model year.

When the battery becomes sulfated and resistant to charging you will see the continual high output that you described with your original battery.

For now, I'd say, operating as designed.

Rob


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## jblackburn (Apr 14, 2012)

What's the voltage of the new battery w/ car off? If you have push button start, hold the button with foot off the brake pedal til it turns green.

And yep, mine slowly builds up to 14-15 if needed.


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## snowwy66 (Nov 5, 2017)

Will post in the morning. Car just got parked for the night. 

I've been holding the button down to activate service mode. The old battery was 11.9 to 12.0. The new battery seems steady at 12.2 with or without the lights. 

On my next day off. I'll climb in the trunk and use an actual volt meter with the car off. I've ordered a new volt meter that does amps also so i can see what the draw is while the car is off. It has a clamp that goes around the cable instead of tieing volt meter in to the connection. ( stud to cable )


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## CRUISE-CRUZE (Nov 8, 2010)

For the ECO version, that electronic controlled battery charging mode never worked properly on my 2011 Cruze! I replaced 3 batteries and the dealer kept telling me "this behavior is normal". Well... it is not! It is NOT normal that the computer allows to "charge" only 12.2V in certain conditions then recovers at 15+V for short time! For a year and a half now, when I changed the last battery, I disconnected the ring (sensor) from the negative cable. That sensor sends the info to the computer and lets it to "decide" the voltage allowed to recharge the battery. Without it, the alternator is charging most of the time ~14.2V. When it's cold, the charge goes sometimes up to 15.1-15.2 then back under 15. The battery never had an issue since that. I was curious and just measured the voltage. Without driving the car for ~24h, the gauge indicates 12.4V. The car is outside, 8F right now so I think it should be ok.


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## snowwy66 (Nov 5, 2017)

jblackburn said:


> What's the voltage of the new battery w/ car off? If you have push button start, hold the button with foot off the brake pedal til it turns green.
> 
> And yep, mine slowly builds up to 14-15 if needed.


The problem is the DIC. It's not LIVE information. It's delayed. 

Connected a handheld voltmeter to battery AND ran obd2 alongside. They're more accurate and live. Both showed alternator functioning as it should. Battery however. Showed 12.4 after sitting all night.

Starting to think these glass batteries SUCK.


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## Taxman (Aug 10, 2017)

I don't see how the charge management system conserves energy. Think about the embedded energy in making a new battery every 2-3 years instead of 5-8 years. 

I'd just as soon see little or no charge on cold start for a while to keep the load off the engine until the oil's flowing nicely, followed with 14v until the battery is charged, then hold the fully charged battery at 12.8-13v for the rest of the trip. I bet the increased fuel consumption over current management software in our cars would be less than a gallon per 10k miles.

Hmm, is this something that one of our aftermarket tune vendors could easily change?


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## ChevyGuy (Dec 13, 2014)

Keep in mind that the BCM is able to monitor the current going into the battery. If we're only looking at the voltage, we're only getting half the story.

Note, if you'd added any connections to the battery (such as for a stereo), you might want to review how it's connected. Depending on the details, the BCM may be mistaking current going to your add-on as battery current. That will adversely affect charge management. The right way to do it is to either connect to the frame ground, or route the wire thought he current clamp so it can be subtracted from the current going to the battery.


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## snowwy66 (Nov 5, 2017)

BCM means body control module. Doesn't it? 

Obd only reads ECM. Or did things change?


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## carbon02 (Feb 25, 2011)

I found this table as interesting information on the Battery Open Circuit voltage vs. status of Charge. Lately some of us have had temperatures around 0F. Don't forget that 12.3-12.5Volts measured across the terminals is over 75% SOC (State of Charge).

Car battery SOC Vs Open-circuit voltage.


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## jblackburn (Apr 14, 2012)

carbon02 said:


> I found this table as interesting information on the Battery Open Circuit voltage vs. status of Charge. Lately some of us have had temperatures around 0F. Don't forget that 12.3-12.5Volts measured across the terminals is over 75% SOC (State of Charge).
> 
> Car battery SOC Vs Open-circuit voltage.


Ooh, good info!


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