Corolla 2.0 EV Battery

[Cjohnston1982]

Hi,  a couple of weeks ago I picked up a Corolla 2.0 Excel and I have noticed something different about the EV Battery setup. In a Prius and Auris 1.8 the Battery will charge on the motorway until it’s 2 bars from top which is “full”. However the 2.0 Corolla doesn’t seem to charge at all once it’s got to just 3 bars full even though it says it providing energy to the Battery. It I have noticed it’s much quicker to recover energy when braking though.

My MPG is between 50-60 which seems about right but I just want to know if anyone else has noticed this?

[AndrueC]

That seems to fit in with what I see on my 1.8. The only time I've seen it actually approach full charge has been when on a long (very long) downhill stretch. But I suspect this is by design. If the Battery actually becomes fully charged the car loses one of its key features - the ability to harvest wasted energy. Thus the ECU probably chooses to stop engine-driven charging before full to ensure there's always space for braking generation.

There are conversion loses involved in putting energy into and taking it out of the Battery. Thus it doesn't make sense to put an extra load on the ICE just to charge the Battery. It's a complicate balancing act. The ECU has to balance the increased fuel consumption from charging the battery with the reduced fuel consumption from discharging the battery, factoring in the losses involved in that process. Since it can't see into the future it has to make a best guess and at some point it probably just makes more sense to stop charging the battery from the ICE and leave space for deceleration harvesting.

[AndrueC]

But on the subject of mysteries I'm still intrigued why the engine is now taking longer to actually shut off when dropping into EV mode. I've read that it's temperature related and it must be because when I first got the car as soon as EV mode activated RPMs would drop to zero. Since the end of spring the engine tends to sit idling at 1,000 RPM for quite a while first.