Understanding IMA behavior, HV battery condition

[eq1]

I've been driving my 2000 MT Insight, ~167k miles, for about 400 miles now. I assumed the battery was bad, going bad, when I bought the car. I've been mostly getting the car up to snuff in the maintenance department, before I try to recondition the HV battery stick by stick...

In general I've been trying to avoid assist. I used it earlier, got some recals, and at one point the IMA light came on. The DTC was P1449-78. I reset. Since then I've really avoided assist and have mainly kept the battery 'topped-off', at least in terms of the SoC dash gauge. The gauge has mainly been teetering between 19 and 20 bars; I can use a little assist and it will drop to 19, and then I can do some regen and it will top back up to 20. I can then do some more regen up to a point, and then it stops, I presume because the battery is as full as the BCM will let it fill...

So here's the behavior that's puzzling me. I used more assist than usual this evening - though still not much at all. Like an 8% uphill grade for maybe 5 city blocks, assist at maybe half to two-thirds on the assist gauge. When I got to the top of the hill, my SoC gauge started ticking down, down, down until it hit about 2 bars. The charge gauge went up to about 4 bars and stayed there, as the engine charged the battery for the next 30 or so miles of driving...

Overall, after the SoC gauge dropped to 1-2 bars, I drove about 40 miles. Over the first 30 miles or so the engine-charging stayed at about 4-5 bars, while the SoC gauge slowly climbed to about 10 bars. At some point this 'engine-charging' stopped, and the only charging was happening when I coasted in gear. Normally I can tap the brakes and the charge shoots up, or at least the charge gauge does. But I wasn't able to do that. I tried to make it do that in the last 10 miles or so; the only time it would do that was if I turned the car off and re-started it. The first braking regen would cause the charge gauge to shoot up (near all bars lit), but thereafter the braking wouldn't do anything, just coasting charge. At the end of my 40 or so miles, the SoC gauge came up to about 14 bars...

So, what among this is 'normal' behavior? Is this normal for a bad battery module, more or less normal for a good battery module? Or, perhaps the question is, What parts of this are normal for a good battery and what parts are normal for a bad battery? The last time I saw my SoC gauge drop I didn't have this long charging period; I think I got a negative recal and then a positive recal - all the gauge movement happened over a relatively short time. I'm wondering if this seemingly long time it's taking to charge back up means I'll actually have some juice in the battery from which to draw some assist...

Anyway, and insights appreciated. This was supposed to be a short question...

[Willie Williford]

That behavior seems normal for a "weak" battery, not a "deteriorated" one.
A negative recal will emit a IMA light un-normally. The SOC gauge is only a reference, and not an indication of the actual condition of the battery. The "hidden charge" is another monster to understand.
The charging system in the IMA setup has a mind of it's own (in my opinion.)
Get yourself a ODBIIC&C gauge and monitor the charging of the IMA battery and you will see what I mean. As far as th IMA battery going dead, I can say that I have ever seen one.
Others will chime in, but that is my opinion.
HTH
Willie

[Eli]

It's all "normal" behavior. But it shows that your battery may be weak.

The first event, with the SoC bars slowly ticking down to empty, is called a negative recalibration. Willie is a little mistaken; a negative recal doesn't normally throw an IMA light, it just depends on the context. The car is monitoring battery capacity when it looks to throw IMA lights. If discharge or recharge capacity is 10% or less, you will get the IMA light.

Not being able to get any regen could be a sign that the battery was getting too hot. That would be my guess if the SoC gauge was only at 14 bars when this was happening.

Being able to charge the battery up to 14 bars and still not have a positive recal is most certainly a good sign. Your battery may not be as bad off as it seems. It's possible that the car sat for a period of time before you bought it, causing the IMA light?

You'll just have to keep monitoring things. I commend you for paying such close watch to the dash cluster. Most people don't.

But yes, an OBDIIC&C Gauge would be a huge Insight into the condition of the battery.

[eq1]

Thanks to both of you. I've been reading a lot and trying to get a handle on things. I'll be getting a C&C... I'm just about to dive into rejuvenating my HV battery. I thought I would charge it up with the car as much as it would let me before I take it out and do each stick... I was hoping that perhaps the fact that the battery seemed to be charging for a while was a good sign, or a better one...

[Hybrid-Battery-Repair]

Originally Posted by eq1

The DTC was P1449-78.

A 78 code is a battery that is still functional, but is now functioning below 10% of its' original 6.5Ah capacity. By definition, the battery is well balanced, or you'd have other errors instead.

In our experience, all 20 sticks will need replacing for any 78 code ( P1449-78 P1433-78 P0A7F-78 ).

[JohnVirginia]

Originally Posted by Hybrid-Battery-Repair

A 78 code is a battery that is still functional, but is now functioning below 10% of its' original 6.5Ah capacity. By definition, the battery is well balanced, or you'd have other errors instead.

In our experience, all 20 sticks will need replacing for any 78 code ( P1449-78 P1433-78 P0A7F-78 ).

OK now I'm trying to make sense of 10% of its' original 6.5Ah capacity. Is the info at Frequently Asked Questions (FAQ) - DC Battery Specialists applicable to NIMH? Are batteries batteries when discussing Ahs? If reading this site is applicable my conclusion is since our batteries are in a 120 cell series connection (each cell rated at 6.5Ah), then the whole battery is 6.5Ah (nominally when new). What charge (amps)/discharge and hours are used to get this number for the Honda battery? There seems there could be an infinite (but countable)number of answers. What values of charge/discharge and hours are used to arrive at the BetterBattery 8Ah value? To compare batteries using this measure wouldn't you have to be using the same values?

Isn't the car capable of discharging at 100amps (before the 100 amp fuse blows?). So at this discharge rate (100amps), wouldn't the battery discharge almost instantaneously? 100 amps times .068 hrs (4.08 minutes, 244.8 seconds) equals 6.8Ah even when new i.e., 4.08 minutes of heaviest assist with no DC-DC outputing for other draws. If we go to 10% capacity, then we could only get .408 minutes of assist at 100 amps.

If the car is using 10 readings of voltage, one from 2 stick pairs, and maybe time and/or a reading of total current (amps) maybe during an assist, would this logically be compared to a similar value for a "new, nominal" battery to get the 10% (1449-7 code setting threshhold?

Too many questions, to long of a post?

[Eli]

I don't think Ron's statement is entirely correct. That isn't to say it's not correct period, but I'm pretty sure that a pack with a single bad stick can and will throw a P1449.

This is because it's based on the negative and positive recalibrations. If the bad stick becomes empty causing a negative recalibration when the good sticks are still nearly full, this will throw a P1449. Likewise if the good sticks become completely full causing a positive recal before significant charge is inputted, this can also throw a P1449.

Will answer some of your other questions when I get home, lol.

[eq1]

Quick update: So, as I had described, I have an iffy HV battery that threw a 1449-78 code about a week ago, I reset, and since then I've driven maybe 120 miles or so. I try to avoid assist. The other night a short, 5 block or so, 8% grade uphill assist took the SoC gauge from 20 to 19 to minus tick tick tick 2 bars. After that I drove about 40 miles, with engine charging the HV battery the first 30 or so, then coasting regen, which ultimately took the battery up to about 15 bars. The next day I was able to fairly quickly take it up to 20 bars.

Today I drove another 15 miles, went up the same hill, same route, and assist took it down to 19 bars, but that's it. I used assist some more, like getting on the freeway, but all in all, it never went below 19 bars, and I was ultimately able to top off the battery with coasting and braking regen down a hill a couple times.

Now I'm going to take the pack apart and look at each stick...

Overall, I don't think the battery is as bad as I had thought when I bought the car. I think it wasn't driven very much in the days or weeks prior to the sale, and that weakened the battery. My driving since then has probably revitalized it to a degree...

[JohnVirginia]

Originally Posted by Eli

I don't think Ron's statement is entirely correct. That isn't to say it's not correct period, but I'm pretty sure that a pack with a single bad stick can and will throw a P1449.

This is because it's based on the negative and positive recalibrations. If the bad stick becomes empty causing a negative recalibration when the good sticks are still nearly full, this will throw a P1449. Likewise if the good sticks become completely full causing a positive recal before significant charge is inputted, this can also throw a P1449.

Will answer some of your other questions when I get home, lol.

I seem to remember Ron saying on a post that batteries throwing a 1449-78 code in his experience usually had to have a large number (all?) of the sticks replaced and he did not make any money on those battery repairs. So, I guess it is possible, but not likely based on his experience, to have just a single stick bad?

[Eli]

Just remember that the car is almost sinister in the way that it hides IMA problems until the IMA light comes on.

The only way to know how your battery is doing is to log the charge/discharge as the car sees it.