Automatic B-mode at 84% SOC

[eurosteve]

So it's true... I've been wearing out my brakes all these months during the last mile of my ride home when I have all green bars. Is there
any downside to running in B for 3+ miles each day?

[DaveinOlyWA]

interesting on the B mode. refresh my memory, exactly what changes happen when B mode is enabled. i know about higher regen, but the engine changes sound as well so something has to be going on as well...

i wonder, if car conditions can be manually duplicated by the driver with slight braking in certain conditions that might make CANVIEW think the car was in B mode?

[efusco]

Dave,
During the "B-mode" regen can be a bit higher early on (SOC <~80%), but once the battery tops out regen stops and there's actually a negative flow from the battery. That's the condition I observed the other day...I was seeing about -5 amps (variable) with ICE running around 2300-3200 rpm.

[DaveinOlyWA]

oic... the negative flow would be hard to reproduce... what causes the engine to change pitch?? its sounds like downshifting?

[efusco]

Originally Posted by DaveinOlyWA

oic... the negative flow would be hard to reproduce... what causes the engine to change pitch?? its sounds like downshifting?

I think it's just the high RPM with minimal fuel flow.

[JimboK]

Originally Posted by efusco

I think it's just the high RPM with minimal fuel flow.

OK, here's a question I've been pondering recently. Is there any fuel flow? I thought I heard someone say there wasn't, but I don't have time to search for that now. Hobbit's article on B mode describes the engine as "spinning," implying (to me anyway) that there is no fuel flow. I didn't think to look at fuel flow or injector timing during my descent Sunday, though I'll have that in my data capture, assuming it is reliable.

[efusco]

I'm pretty sure there's some...but I think it's very little....

[DaveinOlyWA]

on fuel flow, i seem to remember that there was some but what you would see when idling...like .1 gph...or something small like that

[hobbit]

I saw this any number of times in the process of coming from
the west coast to Denver, where I am now, up and down significant
rises and falls. "D" mode starts behaving like normal "B" after
SOC reaches 80+, and when you're at that level then "B" thrashes
the engine much harder than when at a more normal SOC. I generally
quit using "B" after topping out the pack, and stay in "D" to
let the engine still bleed off some energy but not quite as
fast, as I carefully modulate the brakes to take up the rest
of it. Oh, and no fuel is injected during any of this, at least
until you start pressing the go-pedal again whereupon you'll
get into a killer 40-amps-pushing-the-car warp-stealth mode for
a while until the SOC gets back down.
.
Being able to manage this and cut your losses is key to maintaining
good MPG in the mountains.
.
_H*

[ken1784]

Hi,
A lot of Japanese Prius drivers experienced such "automatic B-mode" at 80+ SOC.

Originally Posted by JimboK

So apparently high battery temperature is not an absolute criterion for "EV deny," and instead the car's desire to reduce SOC is a greater priority at 80+%.

When I saw 82.5% SOC, the battery temperature was 50C and I could not activate the EV switch.
The "EV denied mode" was continued even the SOC down to 60's.
I tried many times to activate the EV switch, then I finally could do it when the battery temperature became 45C.

We see no fuel usage during any B-mode.

Ken@Japan