Driving in "B" Mode Regularly

Suits better to the driving style?
Some people prefer the instant feedback from actively using the accelerator in traffic. Others, like me, prefer to minimize speed changes and see dynamic cruise control as an automated speed control. For example, a former supervisor once gave me a ride in his high-powered car but in traffic he was constantly changing his speed enough that I started to get car sick. It turned out he was a former, Naval pilot and I realized he was just doing 'formation driving' in traffic. In contrast, I'm like the transport or bomber pilot who prefers to setup the vehicle and optimize its performance for distance.

Higher efficiency?
This is a hard question because local traffic patterns play a role. I am reminded of DC rush hour traffic that over the years changed from professional, share the road to more cut-throat, fill every gap. The original post in this thread was how "B" appeared to preserve EV charge better than "D" in driving and no mention of dynamic cruise control in traffic. But if I were to use my typical, dynamic cruise control in DC rush hour traffic today, between 'road-rage' and constantly being cut-off, I might not reach the 28 mph minimum to engage cruise control.

My first experience with similar traffic was in the 1960s when our family took a vacation drive from Oklahoma to Bar Harbor Maine. We drove through Boston: (1) horns somewhere were always honking, and; (2) all cars, even new ones, had dents. I would defer to @bisco if this description is inaccurate but that is what I remember. In contrast in Oklahoma, if four cars reached a four-way stop, there would be nearly 20 seconds of everyone waving the others on. In Boston, I imagined all four cars would charge into the intersection at once; slam the brakes and hit the horn, and; fastest one would give the one finger salute to the others who returned the favor.

I prefer a laid-back, less stressful drive where I manage the car and make strategic decisions about how to get where I'm going versus hyper-aware of every car within denting distance.

Better safety?
It is a question of style and I prefer to automate as much as possible since being human, I can be distracted. I like the accurate speed and distance metrics that in sub-second intervals monitors what is in front and uses PID logic to adjust the throttle. In effect, speed control is automated to not hit the car in front. For me, this 24x7, never tired, never distracted yet critical function is something I welcome outsourcing to TSS-P.

Unless local traffic, cut-throat style, rush hour traffic, requires use of "B", I would not use it. I think it can make more sense than "D" in active-aggressive traffic but I prefer dynamic cruise control. I realize my style of driving would drive others nuts ... like my lead footed wife.

Bob Wilson

 

it hasn't changed, but i've seen the same in every city i've driven in. worse in manhattan, and when i was in london in the early seventies, the intersections were so frightening, they were chained off, with underground pedestrian tunnels. city life, some people like it.

 

to add my 5 cents.
I found DRCC very convenient as well, but it seems ( to me) less efficient in irregular stop & go traffic.
It brakes to late and accelerates too fast in dense stop&go traffic (at least for my liking).
Recently I started to exclusively use "B" in E/V in such conditions and found my e/v range and eco driving scores increased noticeably.
e.g I never had 99/100 score before.
Let's see how it plays on longer run.

 

I've been tweaking the following distance and it provides some relief at the maximum, 3-bars. But I'll move it down to 1-bar if we have a lot of 'cut-in' going on.

I also noticed ECO/NORMAL/POWER appear to modify the dynamic cruise control performance. I'm using NORMAL because ECO seemed to have too much lag and POWER too fidgety.

Bob Wilson

 

Thx for tip. That is interesting - another setting to play with .

My major issue with DRCC in stop&go ride is how it handles while changing lanes by Prime and other vehicles in dense irregular traffic.
When the traffic is stable tweaking DRCC distance etc. works well though.
At the end of the day I tend to switch between "B" mode and "D" with DRCC on regular basis.
I wish DRCC would work in "B" mode so I could benefit from it's ability to hold Prime behind the preceding vehicle while stopped and I could take my foot off the brake .

 

Don't need B-mode for that. In fact, you don't need B-mode at all in DRCC since it does it itself.

 

In my liking it is other way around: having DRCC to hold the vehicle while in "B" mode would be nice, or other way of achieving "hold' functionality in Prime to ease the stress on your foot during prolonged stops in traffic - just wishful thinking.

 

If you are using DRCC you don't really need the B position as D with DRCC is by itself a "progressive" B and you have the hold of creeping.

 

I'll just add my little experiment. (My trip from home to work is mainly downhill, from 2000 ft to 376 ft) I started with 24.7 EV miles, and by the time i got on the Freeway it had dropped to 21.2 EV miles. Highway 2 starts off of the 210 and descends to the 134. It's all downhill. Usually, the car regenerates on it's own and pretty much maintains the EV miles. By the time I get to work I usually end up with about 15 EV miles and have covered 21.3 miles total distant NEVER starting the ICE.

This morning when I got on the 2 and began the descent I shifted into B mode. about 60 seconds later the EV went off automatically and the empty car symbol came on! UGH the ICE came on to burn off the excess recharge. No bueno for me. Why it does this when i only went back up to approx. 22.1 EV miles really surprised me. I took it off of B mode before I reached the 134, but the ICE had already gone into it's warmup mode. In this example, i did end up with more EV miles (maybe 2), but at the cost of burning Gasoline!

Just to note, I'm going against traffic so there really isn't any traffic that slows me down other than hitting the brakes to prevent me from picking up too much speed down the hill under normal circumstances.

 

There is a lesson here:

Do the experiment and try to describe the conditions enough that others have a chance to replicate. Then look at how to quantify the effect(s).

Bob Wilson

 

I did an experiment this morning. I took the prime to 55 mph and broke hard regen down to 10 mph.(Keeping the blue line just above the bottom). I did this a total of 4 times in a row. Then I stopped and felt the front brake rotor. It was still ambient temperature.

 

The system has routines for protecting the battery. Perhaps the rate of charge going into the nearly full battery pack while in B was generating too much heat for the system's threshold. An Energi owner here as stated the ICE will come on when the battery gets too hot. Then it is better to slow the charge rate near the top of the battery's capacity for the pack's health. So just charging too fast could have been the trigger.

 

I'm almost positive that's what is going on here.

 

Summer reports might get interesting here.

 

Steve, I haven't had the car as long as you or others. I'm trying to learn as much as possible about it, trying to maximize my EV range. Yes I have range envy! Hehe.

My drive isn't conducive to getting the best mileage. And I'm running into roadblocks in trying to use 'B' when I can bank the most charge because I'm running into the limits of the system. Mainly getting only up to ~80% of my original charge before the ICE kicks on stymying my quest. Granted my descent is steeper than most.

I guess I'm not a good candidate to use B mode on my commute, but maybe on a longer road trip it can help me.

 

With a steep down slope at the beginning of your commute, not fully charging the Prime is something to look into.

 

I actually think an opposite mode would work better - where letting off the pedal results in coasting. Doing that seems to result in better overall miles/kWh numbers. This makes sense if you use it to coast more and regen less since regen is less efficient because you are just putting power in just to later take it back out.

 

At least on regular Prius, keeping slight pressure on gas pedal dispels regen, keeps you coasting.