I Just had my first annoying "excess battery power burn off" issue.

Honestly I have never noticed that.
Not saying it has never happened, just that I have never noticed it. I THINK I would have as I keep a pretty close eye on it, but who knows.
Anyone else?
I am curious now and will try to recreate the effect.
How far down does it drain until you stop getting that type of behavior?
Did it stop when you started driving?
Were you running the AC/Heat or other draws?

 

I have heard of this rather odd behavior, but never happened to me. I had topped the battery many times when driving in the mountains, but the car just ceased to regen and went to friction braking, as expected - I could perceive the change quite obviously. At that point, I switched to the "B" mode. The car never did anything odd or unexpected, it behaved just normally - I never experienced anything from what you describe. Maybe I have newer firmware revision which fixes this kind of behavior? do not know.

 

Never happened to me....

 

How about the EV switch? Do you have it installed?

Well, my car would just go on the battery by itself until it dropped to the blues again whenever I topped it. It would not start the ICE unless I step on it rather harshly or went faster than warp speed. Just as you would expect, so I never had to use the EV button to discourage it from starting the ICE. But in your case, it might help.

 

Sounds normal to me. I'm not sure what is so annoying or nonsensical about it, though. I'd rather have it spin the engine than damage the battery.

 

Sorry, I don't get your point - how does spinning the engine protect fully charged battery?

 

I did not propose anything - surely not to jump traffic lights .

Well, mine never did that even when I stopped with 8 green bars (and I can recall few occasions when I had to stop on the crossing directly after a steep descent). When I accelerated, I did so solely on the battery and did not have to engage the EV mode. Might possibly have to do something with the firmware, as yours is 4 years older than mine - do not know .

But I read about this behavior and it is considered normal, so I would not bother. Look for example here:

http://www.techno-fandom.org/~hobbit/cars/prius-rally-hints.txt

Read the 4th article about force-charging the battery. It mentions the behavior you experienced - quoted as "normal". I believe Hobbit also has an 04 Prius...

Hey, I just remembered something - once when I was driving in the mountains, my good ol' Pri also preferred the ICE, although it had the battery fully charged. It was very hot that day and the car already had more than 200km of hilly ride behind it, so the battery was used extensively. The Battery was hot - I could hear the fans running at the rear of the car - so that was most likely the reason. It also refused to engage the EV mode at that time - however, it would not start the ICE when standing. Everything went back to normal after the battery cooled down. Was your battery hot? Did you hear the fans running?

 

Yep, that is the only way I can think of too.

 

Toyota has programmed the car to maintain SOC within 40 to 80% of maximum SOC to obtain the longest battery life. When the battery reaches 80% SOC (all green bars) then the car will attempt to lower the SOC to stay in the 40 - 80% range. One method to use battery power is to spin the engine using MG1.

 

Thanks, so that's exactly what uart deduced . Spinning the engine using MG1 makes sense; I thought the ICE was started and running by itself, which would be useless. That's why I did not understand at first.

 

I've definitely seen it. When I was driving from CA to WA and watching ScanGauge. Normally, if I'm off the gas coasting at highway speeds w/o a hill, I see about 19 or 20 amps of regen (shows ~-20.x BTA) and I can see the ICE is running at low RPMs. When the HV battery got too full, I saw ICE RPMs well >3000 and BTA being positive (no regen, instead a drain). soc was at or a bit above 80%.

On my new commute, I have to go down a long hill and sometimes the HV batt gets too full (to 80%) and I see the same behavior. Oh well. I wish I had an EV button to drain the batt a bit before starting down the hill.

edit: Yes, I know this is normal. I just was never able to observe the phenomena myself until I got SG.

 

As dogfriend stated this is normal operation of the vehicle when the SOC reaches full bars to protect the battery with ICE burnoff.

I would much rather have the ICE working to burn off energy than be in a low SOC when the ICE is running to help charge the battery. Not only is the ICE running to charge the battery your power is also drastically reduced when using the GO pedal as power is diverted to recharge the battery. Often times you will see high RPM's in low SOC because of this power diversion.

 

I think its all normal.

It used to happen to me everytime i descended a particular long gradient where the engine would be warm after making an initial climb and the battery would have been reletively low at the top of the hill. By the time I got to the bottom, battery would be fully charged but the ICE would be running. EV would not engage but ICE swithed off after aboyt 400 metres.

Got to see if the same thing happens with my 3rd gen car which I've only done 600 miles in.

i'll let you know.