The old 8 bar blues (well actually 8 bar greens).

Hi
This is my first post and the issue sounds somewhat like mine.
I bought a 2005 Prius with 236k miles this summer. 3 months later I am finally starting to just drive it without thinking about everything. Just after I replaced the worn tires, I experienced engine revving accelerating down on-ramps where before it had been a quiet, thrilling experience. At that point I was getting 45 mpg around town. The engine revving often produced little noticeable benefit. Yesterday, it was 70 degrees when I started it up and backed out with the engine running and 7 green bars showing. The engine has never run under those circumstances before. Memphis is not hilly and I am now getting a lot of green SOC in town.
( My 12v. battery is at 12.3v without load and drops to 10.6 fully loaded ign on.)
I have ordered an Obdlink SX and intend to read the battery pid's to determine definitely if I need to plan on replacing the HV battery or possibly just a cell or 2.
Can anyone offer any suggestions on what I may be overlooking?
Thanks,
John

 

In my 2005 I see 8 bars on a regular basis. Maybe I'll be at 8 bars for a few seconds or a few minutes but the charge varies all through the drive.

I never see them long in the hottest part of summer because the AC use drains the battery.

I never see them long in the coldest part of the winter because the heater use drains the battery.

But on the right kind of trip and weather I see 8 bars as often as 2 or 3 times in a day.

But even though I've seen 8 bars dozens, hundreds, if not thousands of times I've never heard the HV battery fan. I'm sure it's back there doing it's thing but it's not doing it louder than tire noise, wind noise, radio noise and even when I come to a stop with the radio off or turned down I don't notice it. Maybe next summer I'll get someone to drive the car while I sit in the back seat so I can listen to the HV battery fan.

I'm sure it's an issue with a Prius in a hot climate but apparently my climate isn't hot enough to trigger behavior loud enough to easily notice and I've driven in mid 90s F (of course at mid 90s I have the AC fan running at the 2nd or 3rd notch with the temp request at 65 F).

 

After a full year of ownership and one very long, record setting hot summer, I have yet to hear the battery fan in my 2010. Is it audible only in severe situations? Is my solar vent (always activated) helping here?

 

The fan has several speeds (6? 8? 7???). It is usually on, but at such low speed to be inaudible. It will step up as conditions warrant, but it is rare that it comes on to high speed during the middle of a drive. What is more common, especially with an older battery, is that the fan will come on at high when first starting the car, when the car is parked for an hour or two during the heat of the summer day with the battery at 8 bars. Maybe some with PriiDash can capture this. This being November means that it is likely that only a Southern Hemisphere will see this in the next few months.

 

This thread seems to be right up my alley. I have a 2004 Prius with nearly 160k miles. The car has had an excellent service history and the HV battery seems to behave just as it did when I bought the car in 11/2003. Is it normal for the battery SOC to read FULL GREEN? The only time that happens is on a long decent down an off ramp on the highway or a steep hill. Is it safe to assume that my battery is in fairly good health if it can achieve a full green charge? I'd say most of the time my SOC is either 1 bar short of full green or top level blue. Like I mentioned, there doesn't seem to be any degradation of performance from the HV battery. If anyone is familiar with this subject your opinion would be most appreciated.

 

This entire thread addresses one form of age, where, due to a mismatch between calculated SoC and battery condition, 8 green bars can bring an old battery close to full charge, and the chemical reactions associated therein, such that the battery overheats if the car is shut off in hot weather with 8 green bars showing on the display. With each such event, there should be an assumption that one or more modules has vented, which will reduce its capacity, and make failure an increasing possibility.

With an older battery, you may see more periods of green and purple, such as coming to a full stop down a hill from highway speed, or accelerating from stopped to highway speed uphill respectively. With a failing battery, you can expect MPG to fall, as the battery ECU demands charging current more often to try to keep the state of charge balanced. The battery management topology is 14 blocks of 12 cells each. If one cell is severely weakened or dead, the other 11 can compensate, to a degree, by being held at a higher state of charge, but eventually there will come a time, such as climbing a long hill or leaving the car sit for a week, where the dead cell will reveal itself and the car will code.

We see reports here of battery failure beginning at about 8 years, 150,000 miles. But we also have a driver who is at 7 years, 400,000 miles on the original. So failure prediction is multifactorial, going beyond age and mileage.

 

Yes, full green is normal in that sort of situation.

No, you can't assume anything about the health of the HV battery by the fact that you can get to 8 bars.