Battery gauge accuracy

kaypee171 · 11-07-2011, 05:40 PM

I have owned my 2000 manual for about 2-3 months. After the first month or so, I noticed I rarely have the state of charge graph below 4 bars from maximum. At first I attributed this to the way my driving style has changed since I learned to drive it properly. Now I am starting to wonder if my graph is not accurate. My first clue was when I inadvertently left the headlights on and drained the batteries. After jumping it and leaving it running/driving it gingerly, the battery was still struggling to get a good charge built up. Then I got in the car a day later, and the battery went from about half full to nearly full. Then today I dipped into the IMA pretty heavily to get up to freeway speeds safely, and my forced charge was on the entire 17 miles I was on the freeway. This despite never showing less than 2/3 full. I have never had any check lights come on, and my fuel mileage is pretty good (66.5 FCD mpg right now, fill up mpg usually within 3-4 of that). Should I be worried for the battery or that the battery level gauge is off?

Willie Williford · 11-07-2011, 05:50 PM

It went into a "recal" mode. The gauge loses its memory as to the state of charge of the IMA battery. There are numerous posts here about your inquiry, almost daily.
Try to use the "search" function.
HTH
Willie

Eli · 11-07-2011, 06:40 PM

Sounds perfectly normal to me. I'm not entirely sure what your question is, exactly?

The jump from half full to full is called a positive recalibration. It's normal, though undesirable.

All of the IMA gauges on the dash are to be taken with a grain of salt. They're very dumbed down, as the average driver wouldn't be able to understand what is going on if they were extremely accurate and told you every nuance about what the car is doing.

Case in point: You can have up to 11A of regen happening with NO bars showing on the regen gauge, from what I've seen.

It's funny because they dumbed them down for the "average" driver, but all it's done is confuse us technical people that want to know more about the cars systems.

insightbuyer · 11-07-2011, 07:41 PM

Those gauges are not accurate at all. I am starting to cycle the individual battery sticks. before I pulled out the hybrid battery, my gauge showed full bars.
When discharging each stick, each stick is only outputting about 1000MAH, so the battery is only 1/6 full, as full capacity is around 5000-6000MAH.

Eli · 11-07-2011, 08:10 PM

Quote:

Originally Posted by insightbuyer

Those gauges are not accurate at all. I am starting to cycle the individual battery sticks. before I pulled out the hybrid battery, my gauge showed full bars.
When discharging each stick, each stick is only outputting about 1000MAH, so the battery is only 1/6 full, as full capacity is around 5000-6000MAH.

The reason for this is because the BCM detected a supback pair that reached "full" voltage. That's the one you're trying to find!

A recalibration is just that, a recalibration. When the BCM sees that a voltage tap has reached full, your SoC gauge fills up and that's your new capacity. If your new capacity is below a certain amount, you will get an IMA light, either P1447-77 or P1449-78 signaling that your battery is on it's way out.

The SoC gauge is dynamic, not fixed. It constantly changes. I don't think it's infinitely scalable, but I do think it has a certain range.That's one of the reasons why I've wanted to get video logging setup in my car, so I can watch both the dash SoC gauge and the BCM Gauge SoC percentage to see if I can make any correlations.

This explains how it works.

kaypee171 · 11-07-2011, 08:21 PM

I'm sorry, but I never understood the need to dress someone down because they didn't recognize an issue from someone else's thread. I have read about recals, but I guess I didn't understand until now. Thanks for the condescension though Willie. You spent more time talking down to me than it would have taken to put a link to a recal definition.

Thank you, Eli and IB.

Cobb · 11-07-2011, 09:10 PM

Thx, this post has helped me too. I was about to ask about the relationship or delay between the 2 meters. Just watching the soc screen and the enginer light it looks like a good 30 second.

Sent from my Autoguide iPod touch app

AbCaRed00 · 11-07-2011, 10:11 PM

Quote:

Originally Posted by Eli

This explains how it works.

Very interesting... Can you please state the location of your source?

Cobb · 11-07-2011, 10:14 PM

http://99mpg.com ? Mike D2K?

boogetyboogety · 11-08-2011, 08:04 AM

Quote:

Originally Posted by kaypee171

I'm sorry, but I never understood the need to dress someone down because they didn't recognize an issue from someone else's thread. I have read about recals, but I guess I didn't understand until now. Thanks for the condescension though Willie. You spent more time talking down to me than it would have taken to put a link to a recal definition.

Thank you, Eli and IB.

I hardly think you were "dressed down" for not doing your due diligence on the purchase and maintenance of a unique piece of machinery. It is a bit frustrating, for those of us who have owned these interesting vehicles for years, done the research, and understand our vehicles and their idiosyncrasies, to read the same basic questions over and over and over from those who don't bother to take the time.

Willie is one of the most-experienced owners here in IC... it would behoove you to listen and research (there's that "search" again!) his sage observations and advice, instead of getting all 2nd-grade-level insulted at one of his friendly pokes...

And oh, welcome to IC...