I will give as much detail as I can here so if someone has had this happen to them, or know if I should have this checked out at the dealer, please post here.

I have 6,300 miles on my 2007 HCHII that I've had for 4 months. My SoC is normally between 5 and 6 bars. I drive the car very conservatively. My last 5 tanks have averaged 51.8mpg with a lifetime 10 tanks averaging 47mpg. I've seen all the strange iFE meter recals and have been in regen now and then so I know what is considered "normal" with my car. So... I had some weird activity with the SoC today...

I was drivng my normal routine on side streets, no A/C but fan blowing (as usual, and I'm not on Auto and the A/C is truly off). It was a beautiful clear sunny day, temp about 86 deg. (according to the temp display). I have 5 bars on my SoC and I pull up to a light and the car goes into AutoStop... nothing unusual. I've only been driving about 10 minutes so no battery overheating situation or anything like that could be possible.

I'm sitting there for about 30 seconds when the SoC starts to go crazy! The SoC drops to 4 bars and the engine starts up by itself. A little unusual here because I've had it down to 3 bars and still stay in AutoStop and then start forced regen after I let off the brake and start moving. Anyway, so the engine starts up (while still sitting at the light and my foot on the brake) and I see 3 bars of forced regen and can hear the engine just putting in overtime trying to charge the battery. 5 seconds later the SoC drops to 3 bars, then another 5 seconds later drops to 2 bars, then finally to 1 bar. I'm still sitting at the light just watching this happen!

30 seconds later, the light finally turns green and I drive about a mile doing about 25-30 mph (posted speed limit) with forced regen. by the time I stop at the next light I'm up to 3 SoC bars. As I turn and continue down the street doing about 35 for another 4-5 minutes, I'm back up to 5 SoC bars. I coast as much as I can to continue charging the battery. By the time I get to my destination I am at 6 SoC bars and everything is back to "normal". I purposely went into EV-Assist once or twice before I got to my destination (after I had 5 bars of SoC) and that was working fine. Coming home everything was fine and nothing else strange happened.

So, does anyone have any suggestions or comments as to what this could be and/or if there is anything I should have checked out at the dealer?

 

See my post: IMA battery crash. I had the same thing happen to me for the first time about a month and a half ago. Since then, it has happened 4 times for me and twice for my wife. My wife uses the A/C, but I do not, and my SoC is almost always 6-7 bars (when not crashing).

I am a little worried about taking it to the dealership, because without an idiot light flashing, I don't know if they will see any codes indicating the problem. I think for as often as it has happened to me, I will at least take it there to log the problem. The funny thing is that it (so far) has only happened in benign suburban driving with little load--not mountain driving.

I think there are two possibilities for the sudden, unexplained crash.

1. Computer brain fart--call is what you will, for some reason the computer goes to Disneyland, wakes up in a panic, and then decides it needs to recalibrate.

2. Some sort of electrical event (a short?) where somehow, when the stars are in alignment (motor/battery/speed/load), something happens to waste a lot of electricity. My guess is that whatever is happening is a quick thing and it doesn't seem to flash any codes.

The first situation is certainly the more plausible option. My car also seems to do the iFCD recalibration samba more than others indicate. I see it 3-4 times every drive, regardless if the ICE is cold or warm. I wonder if there is the automotive equivalent of Ctrl + Alt + Delete where the dealership could reinstall the operating system or something.

 

In some of my older vehicles we used to disconnect the battery on a Friday night and reconnect it on Sunday evening. This was to reset the computers in the vehicle. I am guessing that disconnecting the 12v battery in the engine compartment may not do anything in a Hybrid since it has a battery pack in the back. If its possible to disconnect them both for an extended period of time I bet that would reboot all the computers.

I suppose we need input on this subject from someone who has actually disconnected all the batteries.

 

Is there not an on/off switch on the battery pack? I thought I read something about this a couple of years ago. It was referring to the 2003 HCH. Maybe your 2007 has one as well.
That would allow both batteries to be off-line.

 

I don't know anything about how the recharging system works in the HCHII, but I can tell you this about recharging NiMH batteries, which is the type used in the HCHII. The best practice is to discharge the battery completely before recharging it. This is very different from the familiar lead acid batteries, which never like to be fully discharged. Maybe you were observing the HCH going through a discharge cycle. I would consult a HCH trained service tech.

 

I think its "normal". You can try not allowing the car to autostop at stoplights when the A/C is blowing. It might be worth a shot to see if it saves the SoC bars.

 

But both of us are having the problem without A/C so that's not the issue.

 

I've never seen the bars go down during a forced regen so that is definitely odd. I have seen it go from 5-6 bars to 1 before. Actually it did this twice last month, both times I drove with windows down in the morning and A/C on in the afternoon and it did the drops in the afternoon (I also made new records mpg wise those same mornings too). I'm thinking the half A/C on and half off is confusing the computer - last trip was A/C on so it provided more boost with the battery but since I wasn't using A/C I got better mpg. Then the reverse happens, last trip was no A/C so it thinks the SOC is fine for that level of load until it realized halfway home the extra A/C use and drops my SOC display to 1 bar and does a forced 3 bar regen. Weirdness, temps were 85 in the morning and 104 in the afternoon.

 

I don't think that bit about NiMH batteries wanting full discharge before recharge is accurate. Yes, lead-acid don't want full discharge; and nickel-cadmium *do* want full discharge so as to avoid memory effect.

But NiMH are explicitly designed for trickle-charge and constant discharge/recharge applications. They're what's in cordless phones, for example, and in most non-laptop electronics w/ rechargeable tech (digi cameras, music players, RC cars, etc). They handle high discharge and charge rates well, and have no memory effect to penalize partial discharge.

Lastly, one can merely look at the car's behavior to see that the NiMH packs are intended for *constant* discharge/charge -- just watch the charge/assist meter to see that the computer is always shifting between the two. You wouldn't warranty a battery pack for a minimum of 80,000 miles and then design in an all-the-time behavior that would be destructive to the pack.

--doug

 

True... I believe what you say about NiMH is true (I've read it somewhere myself)... but we are just wondering why does the SoC suddenly, out of the blue drop from 5 bars down to 2 or 1 and start a forced recharge. Most of us that have posted here have NOT had the A/C on nor have had anything major happen before it does the sudden drop in SoC. It's like a surge, short, or a reset is triggered and discharges the battery quickly in 10-30 seconds!