I just bought a 2006 HCH, and only have a week and 300+ miles as my experience.
Just 28k miles on ODO. (Yes extreme low mileage but as far as I can tell this car was always driven, did not sit around long.)

My current ownership average is 42MPG, which is based on my "drive it like a SI" driving habit. So it seems great to get 40+mpg when driving with no care in the world, although I'm not sure if that's how it should be because my assist runs out very quickly (sometimes only sustained at max for a hundred yards).

I am having what I think might be a recal, but I am not sure because many descriptions of recal involve forced regen and I have not had one of those.

I have a long hill climb with 4miles of 55mph steady incline followed by 4 miles of 45mph steady decline. The elevation difference is 500 feet, meaning 2.4% grade up and 2.4% grade down. In the first 2 miles of the climb, the SOC steadily decreases from 7 to 5. 2 miles into my climb, my SOC meter goes from 5 to 3 instantly, then to 2, then assist stops and I have to climb the rest on gas only. It's not too bad since by that time I am already up to speed (55mph). Once I start the decline, the SOC starts steadily increasing from 2 to 3,4,5 bars gradually with the regen lights at 1/4. After 3 miles of mild coasting regen, the SOC goes from 5 bars to 8 bars instantly in a blink of an eye. about 0.5 seconds to go from 5 to 8 bars. Then, the regen bars disappear and the car does not regen at all the rest of the downhill coast.

So, is this a recal? I think that is happen is that: going uphill, the SOC meter thinks I have some charge left but suddenly realizes I have not much left so it goes from 5 to 2 bars instantly. Going downhill, the SOC meter thinks I have a lot of room to charge up but suddenly realizes that the charge is full so it goes to 8 bars and stops charging. So to me this sounds like the pack is unbalanced. Am I right?

I have done this long climb/descent drive 4 times (2 commutes which means 4 drives on this route) and the car has done this behavior all 4 times. The car has not shown this behavior any other time in stop and go traffic.

I purchased a Hybrid Automotive grid charger, discharge-ready version. I am hoping that a balance charge would make the IMA system function with more "bandwidth."

 

I'm not sure if those are the bad re-cals. Normally a bad recal will go from 4 or 5 bars down to 2 instantly (during an acceleration) because there are cells that drop off really fast under load.

In the past, recals would go to 0 bars, but Honda did an update and I believe they don't let the battery go below 2 anymore.

Recals are usually un-predictable. However, when mine got really bad, it started happening every time when getting on a freeway. I had to punch it to get going to speed, and that's when it put a heavy load on the battery and dropped all my power.

The thing you want to try is to see if you can do that commute without getting any loss of power (below 4 bars I believe).

To try this, you need to try to AVOID assist bars, especially more than like 2-3. If you avoid assist, and still get re-cals, then you might have an issue.

I'm guessing you have the latest PCM update but you want to make sure, because the newest update protects the battery better

 

That is exactly what I have though, goes from 5 to 2~3 bars instantly in the middle of a hill climb. Instantly = in 0.5 seconds.

I do think I have the updated software as it was owned by a guy who did all 9 years of service at the local dealership.

 

In my experience with 2 batteries, the grid charging (top off) does not fix the recals. To fix the re-cals you ALSO need to discharge down to 99 volts (which is actually 0% capacity), then top it off again. You may have to cycle it twice.

The last time I did this is approaching 2 years now. I actually fixed the issue. I am doing hard accelerations all the time when I need to.

I still can get down to 2 bars, but its linear without the sudden drops.

 

Discharges are now routinely taken down to <1V for the pack with the Insight folks. This has demonstrated some pretty amazing capacity recovery. Provided you are below 1A @ 120V, the reversals don't harm the cells.

I have taken individual sticks and subpacks down to 0.1V. Capacity recovery is on the order of 20-25% for a given load (20A test load in my case). Same with whole packs. The original fears of cell reversal have been summarily dismissed as unfounded. Mike D REVERSE CHARGED cells at 2A until they hit -1.8V several times. Cycle tests compared to unreversed cells showed no difference between the two. Again, low current reversals don't hurt these cells.

To chime in, this sounds like a recal. Generally, if you ever see your SoC reading two bars, you're in a negative recal.

From my experience "instant" is approximately 1 bar per second. The reverse can happen... you've been force charging in the 3-5 bar range, and it goes to max at 1 bar/second. That's a positive recal.

Essentially, for a negative, the BCM detects that either the entire pack voltage or 1-11 subpacks are showing low voltage for a given current. The car cuts the assist function, sets SoC to "0%" (or 25% given 2 of 8 bars) and enters forced charging mode. It can absolutely kill power and economy.

The opposite can happen... car is charging and the pack or 1-11 subpacks shows peak V for a given charge current. Car resets SoC to "100%" and maxes the bars.

28K is not the result of being driven regularly. Frequent short trips are hard on the pack. If you are no longer under warranty, I recommend you pursue grid charging and discharging. The quality of the original packs is better than the replacements, so you have a decent chance of getting the pack back to a much better state of health. It is likely significantly imbalanced based on your description of its operation.

The longer you wait, the worse it will get and the faster the battery will deteriorate.

Steve

 

Thanks for this real life example. I guess I'll have to discharge as well as balance charge to see tangible benefits. But also good to know that tangible and enduring benefits have been seen by people.

 

Permanent fixes to battery pack issues from grid charging/discharge are rare on the 1+ year time scale.

The faster you act, the better. Pack empty/Negative recals are tripped ultimately by the weakest cell(s). Pack full/positive recals are tripped ultimately by the strongest cell(s).

Pack longevity depends on keeping cells balanced within a true 20-80% range. When recals start happening, weak cells get driven below 20% and strong cells above 80%. Cells cycled in these ranges deteriorate faster. Deteriorated cells cause subpack voltages to sag or spike prematurely thus reducing apparrent capacity.

IMHO, IMA packs are not maintenance-free. they are poorly designed and poorly managed compared to a Prius battery. Quarterly grid charge/discharge can go a long way towards maintaining pack balance in the long run. Nothing magic about quarterly. Certainly at the first sign of deterioration (repeating recals), one should consider grid c/d.

Steve

 

P.S. FWIW, on both my '06 HCH2, I have NEVER seen 2 bars on a car that wasn't initiating a recal. Ever.

both of my cars have the latest updates that are supposed to better manage the battery.

 

Strange. Maybe I do have the old software. I asked the local dealer and they said they can't tell me over the phone just based on VIN.

 

Hmmm. Maybe your dealer is lying or mine is magical. They informed me by VIN that I didn't have the update when I scheduled for one of the recalls (DC-DC converter or something - can't remember).

Now that I think about it, I vote magical. They wanted so much to replace my compressor ($2,000), they must see their services as magical.

Steve