thanks. I will check out that document.

 

My Ascender (Envoy). Does that ,sits above fourteen at times . Dealer is correct the computer does control it, says so right in myowners manual. I wouldn't worry about it.

 

Well, I guess today was "14.0 volt day !!"

quick update on '15 Impala from 57chevythunder:

We took a little trip today up the Big Horn Mountains just west of us. It is mostly a typical 2-lane winding mountain road, ranging anywhere from 65 mph to 25 - 30 on many curves, and moderately steep inclines, etc. First part of trip was about 1.5 hours, then 45 minute break, then about 55 minute return.

The ENTIRE trip, the voltmeter read exactly 14.0 volts. -all the time, every time. (that is, of course, after the 30 second startup mode of 14.5)

So what the heck mode was it running in today ????
(-and why, I might ask,,,,)

My gosh, this is getting crazy,,,,

Anyway, just though some of you might like to have my update on how it ran today.

(this whole thing is almost getting funny,,,,,)

 

15.0 for 38 miles... several startups today. first drive in a week.. daytime.
then 14.9, then back to 14.6 in 3 miles.

I'm at sea level - if that has anything to do with it (other than my lack of driving - generally short trips (<10 miles). I think I'm near 400 miles since Dec 14.

 

WOW Sledge, isn't this interesting,,,,

Okay see if my reasoning makes any sense at all: In your last outing, I assume that your car had not been driven for many days, is that right? -and if that is the case, then I suspect the battery was needing significant re-charging. And given that as a real probability I see on the GM technical document that in the "Charge Mode" the charging voltage should be between 13.9 and 15.5. So, by golly, I'd say your system was doing exactly what it should have done. (and seeing that it was starting to drop down into the 14's after your 38 miles, I would have to assume that your drive was just about the right length to get the battery back to full charge.)

In my case, the battery tender had been constantly floating the battery at 13 volts, so my reasoning is that my battery was already fully charged, and shouldn't have needed any significant amount of re-charge, other than of course that initial "start mode" top off. But maybe for it to have run at a constant 14 volts yesterday is ,,,almost,,,,, logical ???

Quite frankly, I was expecting to see ours back in it's 12.5 volt routine, BUT such was not the case. THANK GOODNESS !!!

So how can I summarize this,,,, At this point I'm okay with saying this: "The current GM "smart charging system" is apparently W A Y smarter than I am."

I'm okay with saying that,,,, really I am,,,,, really.

In a twisted sort of way, this is almost fun,,,,,

Oh, I just have to comment on your 400 miles since December,,,- We must be really "smokin" with ours at exactly 856 miles now, since January !! -at any rate, we sure do LOVE this new car. (this old guy is just going to have to accept that it is way smarter than I am,,,,)

 

OK, not to beat a thread to death, just had to add another two cents worth. On 12 Mar I removed the batt maintainer from the car. 13 Mar started a 400 mile trip. Started car 14.3V for @40 sec and dropped to 12.6 V. Stayed there for 175 miles. Each time I started car over the weekend 14.3V for @40 sec and dropped to 12.6V. While driving at nite 14.4V and stayed there (with head lites on) Next morning started car 14.3V @40 Sec then dropped to 12.6V for the full trip home. I'm starting to think outside temp has a big effect on the operation. All weekend temps were above 55 degrees or the new batt solved my problems.

 

Rookie, first of all let me say "Thanks for sharing". I wish more people would also share their numbers with us all. My gosh, to me that is the whole purpose of these forums. -I think I can identify with your concern about "beating a thread to death" but I don't see it that way at all. Hey, I say for those that only want a simple explanation like "don't worry about it, the computer runs the whole show these days" then that is fine. They can just skip through the thread and pick out whatever tidbits that works for them.

For the rest of us who appreciate more details, then I guess that is why you and I are still here posting replies. I find it very valuable to know how other people's numbers are comparing to my own, and totally appreciate the feedback. (-but I have also been a little concerned that people might think I have "stolen a thread" by posting so many details, and if I have been inappropriate, then I welcome someone to tell me, and I will understand. If that is the case, I apologize)

So how did it make you feel on your trip to see your charging system running in the "Fuel Economy Mode" for the whole trip?? (other than "Start up Mode" with each engine start, of course). I guess my summary is that it was working exactly like the BCM computer was telling it to. But darn it, I still don't like to see them run at less than about 13 volts. This Summer when we start taking some trips, I'm not going to like it running at 12.5 for extended periods of time. I just don't like it, but I am just going to have to get over it. (maybe I'll turn the headlights on, and force to run higher,,,,)

Just a couple of days ago, on a short trip mine was doing essentially the same thing as yours. (other than operating in Headlamp Mode (at 14 volts) for the first part while it was still dark). Apparently these new "smart charging systems" have a preference to operate in the Fuel Economy Mode,,,, It kind of seems like it to me.

And I think you are totally correct, in recognizing the "variables" that are involved, and as I read it temperature is certainly one of them. But what happens to me is that every time I think I should be able to predict what mode it will run in, it shows me that I am wrong. -oh well,,,

Again, thanks for sharing. I sure wish more people would do the same, so we could have more examples of their actual "real world" results.

 

Update about six months later: Well, it has been months since I have seen any voltage values down in the mid-12's. So, HOPEFULLY that irritation has gone away forever. Normal daytime driving values have now pretty much averaged in the 13's, which should be perfect.

Just thought I'd let everyone know.

 

Well, I must have jinxed it with my reply 6 days ago. Today I made a few short trips around town, and every time I checked it, it was running at 12.5 volts.

I sure am glad I always have it on the Battery Tender all the time it is not being driven. This evening I noticed it took a very long time for the BT to re-charge it and get it back into the maintenance mode. -which is a clear indication that the battery was partially in sulfation, probably at about 80 per cent state of charge. To state it another way, GM's "smart-Axx" charging system left me with my battery 20 percent discharged when I parked it tonight. Just think about how nice that is going to be for those cars that don't get driven for long periods of time!!

I still say that GM's "economy mode" is a very bad idea as it relates to battery health and longevity. But what do they care. Yes, I am very unhappy about it, and certainly stuck with their design.

I'd still love to have an in-depth conversation with someone at Deltran in the engineering department to see exactly what they think about operating a battery at 12.5 volts.

"Thanks a lot you smart-axx engineers!!" It is so sad that you almost "got it right" with all of the other charging modes making good sense. But your "economy mode" needs to be reworked. AT LEAST increase the value to 12.6 or 12.7. Then I'd be fine with it.

GRRRRrrrrrr,,,,,

 

Hi folks. I'm new here but I have read all the posts in this thread. I have a 14 impala with 41000 miles. It has started charging at 15.1-.2 volts all the time no matter what accessories or how long it it drove. Its driven everyday and not short trips. It used to vary between about 13.2 - 14.7 which I consider normal. A steady over 15 volts all the time now does not seem normal.