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

Hey uart:
I don't really understand what the colors mean with the Pack ! Mine are showing normally grn. I have notice purple on occasion as well as blue. I think blue means full SOC and purple low SOC? I would really like to know what this all means! I cannot find anything about it in the manual! Hal

 

There must be a level of "supercharge" of maybe super long hill in regen that causes this as I routinely park my car with all green overnight. I forget to ev and burn it off the last leg of my commute.
And I have never heard the battery fan come on. Casual full charge does not seem to affect the battery fan or force the engine come on.

But isn't this is why we have a B gear? The Braking gear? Have you tried
using the B gear down a big hill? It's hard on mileage but takes the load off the brakes and regen. I have never gone down a big hill in the 4 years I have owned my 07 so do not know how effective the B gear works but its there for big hills apparently. I wish they disabled regen completely in the B gear. That would have worked really good to prevent overcharge.

But if regen disabled the brakes would suck. Millions of Americans shouting my brakes went out!!

And your anomalies are pretty common based on reading this many times here.
The engine's constant running to spin mg to to load the hybrid battery trying to burn off the extra charge. Mileage goes in the dumper.

 

Green is battery fully charged. I see it constantly and is not a bad thing.
(See my "overcharge" post above)
Blue is normal charge remaining depending on how many bars.
Purple is very low soc. Empty. Will happen quite often and will force engine on to recharge.
A healthly car should charge back to a few blues from a purple in a mile or so.

Be aware there are software limits to being empty and being full. Reserves if you may.
The software will never allow the battery to be completely empty nor overcharged but apparently you can "overcharge" the hybrid somewhat.
Causing the hybrid pack to heat up turning the fan on.
Then the software turns the engine into an air pump which loads the mg drawing alot of current out of the pack to kill off the supercharge.

 

I use B position on the stick for very steep hills! Works great to keep speed under control without brakes. I live in the mountains! Hal

 

Thats it! Whats the SOC look like after using it?

I have never seen a hill with my car. Damn flatlander.

 

Roger that.

 

Was the engine really running, or was it being spun to burn off excess charge? My guess is that it was doing the burn-off dance, where MG1 spins it fast for a bit, stops, spins again, and so forth until the SoC gets down to a reasonable level.

Tom

 

^^
I drive lots of hills and the occasional mountain. When the ICE revs as part of a SOC lowering cycle, the instant GPM on my scangauge is not zero even when in motion. At the moment I cannot remember a figure

 

I only use B on short steep hills in town. On the open road I prefer to tap the brakes to keep speed under control. The Prius seems to have some engine breaking at all times. My HCH2 just takes off when the SOC fills.[Free wheel] Hal

 

I made a mistake. I don't get 8 green bars I get 7. I counted them tonight. I thought that was 8 bars but there's a little white bar on top I never noticed.
So I guess you have to go down a really big hill and be in regen a fairly long time for it to charge up to 8 bars.

 

uart, you have it spot on, the battery was overheated, and you noticed the driveability problems. It is precisely this type of scenario, repeated several times, that leads to a dead cell, typically for drivers in US mountain states or the superheated South. What gets me is, electric engine cooling fans will run even after the car is turned off...so why not the HV battery fan? I think so many failures would be prevented that way.

A feature of NiMH chemistry is continued heating due to production and reabsorption of oxygen at near full charge. Excessive heat also causes cells to vent, which leads to lower capacity, which leads to eventual failure to do overcharge/discharge.

Question is, why does this seem to happen to older Prii? My working theory is that older batteries suffer from NiMH voltage depression, which leads to a mismatch between calculated SoC and actual. At 8 Green bars, instead of 80% SoC calculated, it might be 95% actual -- the battery is almost fully charged even though the computer thinks it is not -- which is well into the oxygen production region and would explain why the battery temperature goes up after the car is turned off.

 

I've had something similar to that happen, once...but not quite as severe. It only happened to me the other day after driving my 2010 for two years. I was driving in a very hilly area that I normally don't drive in. The battery got fully charged for quite some time, and when I slowed down to work into town traffic, I could not stay in EV mode over 10 mph, in spite of having a full charge. I did not hear the battery fan though. I happened to park the car for about a half hour and it still showed a relatively high SOC, but again could not use EV above 10 mph. After several hours cooling, everything was back to normal.

In my mind, it is better to disable EV if things get overheated than to burn something out.

 

In my 2008, I've only seen 8 bars one time. I actually was beginning to believe that 8 bars didn't exist. Now from reading this thread, I get the idea that if I should hit 8 bars it is a good idea to do a bit of ELECTRIC driving to burn it off so I don't have an overheating issue.

 

A full SoC will not cause overheating. Overheating, on the other hand, will influence SoC. Drawing power for EV mode would only make the problem worse.

Tom

 

True on a new battery, questionable on an old one.

 

True. With a failing battery all bets are off. A bad battery can overheat while sitting idle.

Tom