Battery increasingly full--a problem looming?

As my Prius has aged, I've noted that the car is keeping it's charge level higher. I used to stay in the blue region, now it's green a lot (highway driving). I have 47k miles.

 

I doubt this is a problem. For one thing, the Prius tends to maintain a higher SOC in cooler weather. Part of this is probably the fact that the A/C isn't run, but my observations indicate that there is a programming component to it as well. Another part of this is the fact that the battery capacity is actually smaller when the pack is cool. (That's just how NiMH is.) This is noticeable in the form of a battery that charges and discharges faster than it did during the summer. It could be that you are just better tuned into it this year, especially if your car is a few years old and you hear the voice in the back of your mind saying "I wonder if it's time to for something to go wrong?" Warning signs of a failing battery are **very** rapid charge and discharge. We're talking one bar to 8 bars and back at a truly alarming rate...seconds, not minutes. The behavior you describe sounds normal to me.

 

The warning sign is wild or rapid fluctuations between fully charged and discharged. I believe more green bars more often result from better driving and/or how the car is configured.

 

I've seen all green bars on my Prius time to time. My Prius is slowly approaching 24K and it seems to run better and better as the miles pile up (knocking on wood).

 

As others have already stated, high SOC is not a problem. It's rapidly fluctuating SOC that indicates possible battery trouble.

 

Is the fuel efficiency different from before? I remember reading someone observing the more green bar phenomenon together with lower fuel efficiency. The conclusion was that the battery does get old and not as good as new. Even though it still works, it is not as effective.

 

Well I guess it would be hard to tell until you have a chance to drive in a similar fashion as when you first got it. Yes different tires, short trips and hills all affect MPG. And yes my impression is also that hills kill batteries sooner.

 

At 120K on an '04 my original HV battery seems to be just fine,
but it's definitely exhibited a couple of issues in cold weather.
Less regen current allowed until enough cabin heat slowly seeps
into the pack back there, and peaks as high as 270V during high
charge rates even at the reduced 50 - 60 A limit. That points
to higher internal cell resistance. But it's right back to normal
in warm weather, so I wouldn't be too concerned.
.
_H*