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Every once in a while, usually in the first 10 minutes of driving, my 2009 HCH will indicate that it is charging the battery, yet the charge lever doesn't increase. Then I will come to a stop, the auto-stop engages, and then the charge level will start indicating more and more charge, adding about a bar a second. Recently, on the freeway for 5 minutes, it was indicating at least 3 bars of charging the whole time, but the charge level sat still. Then as soon as I got off and stopped at the light, the charge level added 5 bars (again, about 1 per second) and now indicated that is was fully charged.

I am worried that something may end up causing it to overcharge the batteries. Is this normal? Do other people's cars do this? Does anyone know of a TSB related to this?

Thanks.

Russell

Hi pdxhch

Welcome to CleanMPG.

No need to be worried about it yet. The behavior you described is quite normal under the appropriate circumstances since the actual SoC is a function of several variables rather than just a simple terminal to terminal voltage reading. I actually wish it were that simple but sadly it is not.

As we are getting into higher summer temperatures many HCH-II owners will observe such episodes and the car's instrumentation will often have to reflect what the BCM and MCM tells it to. This is especially noticeable for owners whose cars have been recently software updated. Honda is taking no chances and as such it has changed the rules of the game a bit.

Lastly, this NiMH chemistry is more tolerant of mild overcharge conditions than it is of deeper discharges so I would not worry about the frequent incursion into the 8 bar SoC. Instead, I would want to avoid slowly taking it down to 5 bars more than having it max out at 8 frequently. ;)

Cheers;


MSantos

Hi MSantos. My hunch, particularly post software update, is that "8 bars" is a moving target over time. In other words, when our previous HCHII was brand new, if the dash displayed 8 bars of charge, and I was able to directly measure the battery pack's voltage, I would get some fairly consistant value, say for voltage.

But 4~5 years down the road, after the software update, I would see strange fluctuations in number of bars. Sometimes there would be prolonged charging and no change in qty. of bars. And then suddenly: it would jump to 8 bars.

All of this left me suspicious of the actual state-of-charge. Would it be a fair assumption that 8 bars of charge on an aging pack might be significantly different than 8 bars of charge on a brand new, healthy pack?

Hi Mendel;

Quite right.

The actual SoC has always been a moving target because in actuality several variables have always been used to determine it. As the pack ages and certain charge/discharge episodes are detected, the SoC target line will be adjusted to reflect the new reality and with the new software updates, some of these variables have been given a larger weight which favors a healthier SoC range and lesser chances of dwelling in the lower SoC ranges for too long.

I know this doesn't always amount to much consolation but we urge most HCH-II owners to just ignore the 2-8 SoC dance a bit more. In the end, it remains a game of balancing energy flows and minimizing downstream losses (keeping regens and assists low) since the HCH-II (as with any other hybrid) remains a gasoline powered vehicle. ;)

Let me explain:
Even when incurring frequent 2-8 charge episodes, the overall net effect should still lead to "close" to optimal MPG because it is not like a bulk of the ICE driven regen is going into a black hole of sorts.
Sure, these episodes don't always happen at the appropriate times and can drive many folks insane... but if the driver is able and willing, then these charge episodes remain very manageable and the overall tank FE should not suffer much at all.

Cheers;


MSantos

So I shouldn't be concerned about it indicating for a long time that it is constantly adding significant charge to the battery? At a minimum it was 3 bars, but most of the time it was at 5 or 6 bars on the regen gauge.

And once the care is fully warmed up, it never does this.

Thanks.

Russell