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Discussion Starter · #1 · (Edited)
Hello everyone,

I accidently noticed today that battery voltage on my car is changing in "swing" style while I was driving.
So I had Scangauge 2 connected and displayed 4 parameters including battery voltage.
I noticed first that after start up the battery voltage went to 14V and stayed there for the first part of my trip (40 miles). Then when I exited from the interstate highway and proceeded on the local highway with lower speed (35-50 mph) I noticed the battery voltage started to swing.
Every time when I applied a gas or decelerated to complete stop the battery went to 12.6+/-0.2V. And every time when I glided at high speed (35-50 mph) without depressing the gas pedal the voltage stayed at 13.8+/-0.2V.
The transition time was different when switching high-to-low or low-to-high.
Low-to-high time was a matter of seconds but high-to-low was instant.
I didn't really monitor my battery voltage very often before because I found it quite stable until today.
But on my way back I noticed that battery voltage was pretty stable at 13.9+/-0.2V.
I did not notice the difference in car's behavior when battery voltage was swinging.
I also noticed that if I leave ignition key in 2nd position and let car sit for a few minutes with headlights on the battery voltage drops to 12.4V.
For all of you guru: I would like to know what maybe the root of this problem?
I had my battery tested recently at the dealer (during maintenance) and it was fine.
 

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Hello everyone,

I accidently noticed today that battery voltage on my car is changing in "swing" style while I was driving.
So I had Scangauge 2 connected and displayed 4 parameters including battery voltage.
I noticed first that after start up the battery voltage went to 14V and stayed there for the first part of my trip (40 miles). Then when I exited from the interstate highway and proceeded on the local highway with lower speed (35-50 mph) I noticed the battery voltage started to swing.
Every time when I applied a gas or decelerated to complete stop the battery went to 12.6+/-0.2V. And every time when I glided at high speed (35-50 mph) without depressing the gas pedal the voltage stayed at 13.8+/-0.2V.
The transition time was different when switching high-to-low or low-to-high.
Low-to-high time was a matter of seconds but high-to-low was instant.
I didn't really monitor my battery voltage very often before because I found it quite stable until today.
But on my way back I noticed that battery voltage was pretty stable at 13.9+/-0.2V.
I did not notice the difference in car's behavior when battery voltage was swinging.
I also noticed that if I leave ignition key in 2nd position and let car sit for a few minutes with headlights on the battery voltage drops to 12.4V.
For all of you guru: I would like to know what maybe the root of this problem?
I had my battery tested recently at the dealer (during maintenance) and it was fine.
Not to hijack but this POS Interstate battery I got has drained too eazy on me so I get these slow cranks and somewhat extended cranks on my 06 vtec v6. I almost wish I could go trade my battery in for a new Die Hard or Walmart's one. hell, I would even take an Autozone one compared to this POS!
 

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Battery charging is controlled through the PCM via the ELD in the under hood fuse box.

Being a hybrid, your car charges it's battery not via an alternator, but from an DC/DC inverter. This is all part of the hybrid system.

Your car also can start one of two ways, 12v through a conventional starter or using the IMA. Mainly it should start with the IMA.
 

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Discussion Starter · #4 ·
Thanks, Fred, for clarification.
But I asked about possible reason for such a behavior.
Today I observed exact the same behavior so it is not an accident but looks more like a trend.
I watched more precisely for speed range when this voltage swing is happening.
The bottom border is around 27 mph and match 4-to-3 gear shifting point.
The upper border is up to at least 55 mph on the 5th gear (I did not try to drive faster).
I plan to watch battery voltage tomorrow and report afterward.
 

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OP,

Me thinks you should be watching the traffic ahead more than the Scangauge before you paid too much attention to the Scangauge one too many times and cause a collision.
 

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I have the scangauge as well. From time to time I see the battery voltage goes thru the ranges as well, but then I came tothe conclusion that if the car keeps starting and the lights keep working then it must be working. For the record on my small city drives is when I see the voltage stay low. So I would guess the computer has a preset limit before it starts charging.
 

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Discussion Starter · #7 ·
OP,

Me thinks you should be watching the traffic ahead more than the Scangauge before you paid too much attention to the Scangauge one too many times and cause a collision.
Don't worry. I pay enough attention to the traffic. Luckly where I drive I have almost no traffic at all. I only glance at the screen of Scangauge.
 

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There's nothing you can do about what its doing so there's no reason to be watching it.

Honda is very cryptic, to put it mildly about the their theory of operation of many of their systems. They are the same towards their own techs, very little theory and how the system should operate. It's almost as if they want someone to have to figure out this stuff on their own.

What you're seeing may be perfectly normal and programmed in behavior.
 

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There's nothing you can do about what its doing so there's no reason to be watching it.

Honda is very cryptic, to put it mildly about the their theory of operation of many of their systems. They are the same towards their own techs, very little theory and how the system should operate. It's almost as if they want someone to have to figure out this stuff on their own.

What you're seeing may be perfectly normal and programmed in behavior.
Reminds me of some girls I know.

I'd love to find a good source for system description and theory. The best thing I've come across is some PGMFI training material found from tech2tech and it's old.. 2000ish. Is there any good reading out there from someone other than Honda that you know of since they don't want to share?
 

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Wish I knew of some. It's a pain having to take theory of operation of various systems from other manufacturers and trying to apply it to Honda's systems.

Every company does things a bit different, and sometimes those differences are the most important. They've gotten a little better with their "advanced diagnostics" but many of their diagnostic charts/trees always lead to "replace with a known good part" rather than using various tools and equipment to diagnose the failed part. Replacing with a "known good part" can get VERY expensive and if it doesn't fix it, what does one do then. Many of these parts are non-returnable.
 

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That is obnoxious. Like we all have a museum of "known good parts" to rifle through when something is being diagnosed. And what if the problem damages the known good part before it's found? Maybe it's to keep things from being overcomplicated and making a 10 step flow into 40. But it would be nice to have the choice and a more thorough description of the system since thinking outside the box is often needed. Guess I don't see the point of keeping everyone (especially those wearing a Honda patch) in the dark.
 
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