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

Did you have SOC on scanguage? or just battery bars were all green?

I have had similar, though not same, thing happen to me. SOC was still close to 80 and I was going downhill with coasting for regen. Suddenly engine was revving up.

I realized since battery was full it switched to kind of 'B' mode for coasting which made perfect sense to me.

Revving engine with MG1 does not make much sense to me. This action to protect battery should be done before SOC builds up. Revving engine with MG1 to burn off battery power is like taking corrective action after some of the damage is done.

 

I'd rather dump some power than go battery shopping and in any conventional car that energy would have been dumped anyway.
I suspect there is something of a buffer in the 40% to 80% charge range so no harm is done when this happens. The computer can't predict the future terrain so it can't preemptively dump energy unless you tell it to, hence B mode.

 

What confuses people in these situations is that it sounds like the engine is running, which makes no sense at all. As pointed out above, the Prius uses MG1 to spin the engine without gas or spark. The engine acts as a big air pump, which is used to burn off excess energy in the battery.

Tom

 

If that's the most annoying thing that happens to you on any given day, count your blessings and forget about it.

 

Still seems odd to me. I thought the battery life was extended by only cycling in the middle part, not by not holding it at the higher charge. Once the system allowed the battery to be charged above the target, the damage, so to speak, was done. It was already stopped, so it wasn't about to get energy thrown at it again. The system should have just waited until the next opportunity to use the battery, which would have been when the brake was next released. Maybe I don't understand the battery well enough, but I was unaware that holding a charge was a problem, only that deep cycling it was.

 

Happens to me all the time when im coming off the large freeway offramp, or down some huge hills. Nothing to worry about. I read somewhere the battery can't be "too full" so yeah even when i come to a stop and take off it starts up to run again

 

This happened to me today for the first time. I work up on top of a mountain and coming back down everyday my SOC shows 8 bars (all green). I switch to "B" mode when the battery shows all green when coming down the mountain, but this is not where this happened today. I was on my way back home from the dealership for another issue when my battery reached 8 bars in a spot on a road I drive often. It has never shows full SOC in this spot before. When I came to a stop my battery was showing full SOC and the ICE revved for about 30-60 seconds before turning off. I also have felt like the car has had a lack of power when accelerating in the past few days. Car has 96K miles on it. I've owned it since new and have never experienced this before. Also, when I first got in the car from the dealership the ICE would not turn off for significantly longer than has ever happened before. Any insight would be appreciated. Thank you!

 

Anyone sat in the back who could have blocked the vent?

Otherwise I wonder if it's an early sign of battery failure? Mine was doing something similar when going down a steep hill and got me quite worried for a time. Since then I've had my battery checked (official Toyota health check) and it's fine.

Maybe go get the battery checked by Toyota whilst it's still in warranty (unless you live in one of the CARB states).

 

Luckily, I'm in a CARB state and have some time.

This was the issues I had it in the dealer for: Electric Motor Noise? | PriusChat