B mode: What is the advantage to use B mode when driving, more regeneration? more economy?

Just curious, what are your EV numbers you get with D while in EV? I have never used "B" on my PRIME, but my EV numbers are usually 5~6 without AC.

 

Has anyone determined or verified any mountain descent as being tall enough to fully recharge a Prime via regeneration? I.e. without plug- or force-charging it prior to descent?

 

Based on my PiP experience on Clingman's Dome, I doubt if a Prime that's empty at the top would completely fill up. But I think it would be pretty close one way or the other. My PiP filled up at roughly half way down or maybe a little beyond that. I would have loved to have been able to test that.

 

There's no free lunch lol: first you need to haul your 2 tons of car UP there.

 

Dumb question. What is the correct way to exit B mode?

 

There is if you charge up where's no fee! lol

That is true, but at least you get more coming back down, with the regular Prius you're charged up only a mile down the road.

 

Just shift it back into 'D'

The car won't let you don't something like shift into Reverse or Park while you're moving. I mean if you're rolling at 5 MPH it might slam into Park and of course that's not a good idea to try, but if you're going down a mountain say 50 MPH and you accidentally shifted in reverse it won't do it and probably get a warning message along with the infamous beeping.

 

Move the shifter to D ??

 

Sure it would.
If, for instance, you lived near the TOP of a mountain and started out with a full charge.

 

Which isn't very likely that people live on top of a mountain, in other words what I meant is that this isn't something you would typically encounter.

 

Not free, but GREATLY discounted compared to dragging an SUV up there and then converting all that potential energy into heat and brake dust. It was REALLY cool to start down the hill with an empty battery having gotten about 38 mpg going up and then drive about 40 miles without burning a drop of gas in a car that usually has only about 12-13 miles of EV range. A Prime would be AWESOME up there!!

 

40 miles of downhill drive? What elevation change?

 

I'd guess 4000 feet ought to be sufficient, give or take a thousand depending on conditions and speed.

With some concerted effort, great conditions, and no tailgaters, 2000 feet might even be enough.

 

Well over 5,000 feet. Clingman's dome parking area down to Pigeon Forge which is 30 miles and still a full battery after that. Next day from the same parking area to Cherokee which is 26 miles and about a 4,000' drop. Battery wasn't quite full when we got to Cherokee.

 

When going down a hill using B, if regeneration is not available (battery full or in HV mode), then engine braking will be used (after a warmup cycle). No friction brakes. Same if you press lightly on the brake pedal instead of using B mode. Generally, friction brakes are only used as a last resort if there is nowhere else to put the energy, or in case of an emergency stop. Slam on the brake pedal at any time, and you get the full stopping ability of the friction brakes, subject to ABS to prevent the wheels from locking up.

 

So my thoughts on B while in EV..... One thing is for sure you better be going down something steep. The car will slow down even on fairly steep 8% grades. Compared to the regular Prius, the car would gain or maintain speed under the same conditions. The car does not, like others have said, start the ICE unless you are in HV mode. That being said, use the brakes first until you have some EV range then switch to EV mode to get the maximum charging. If the ICE is running you're not going to get the full benefit.

Generally speaking, brakes (regenerative) vs B, they're going to be close. The Prime will allow up to 40kW in via B or braking (compared to 32 on the regular Prius which doesn't last very long due to the smaller battery). I gained about 5 miles of EV range in 2~ miles down a 8% grade....don't hold me to the distance I'm sure I'm off a bit. This "free lunch" I get does mean I can achieve over 60 MPG without a charge where 50~ MPG was possible with the 2016 Prius.

Bottom line is, if you get tired of hitting the brakes going down a long, steep grade use B. Otherwise you'll find yourself stepping on the accelerator which might work against you.

 

Or use cruise control. B applies a fixed amount of regeneration; cruise control will apply just what is needed to maintain your speed.

 

Yes DRCC will work while in EV mode. For those who do not have DRCC such as a regular Prius you would have to go about it differently, that is if you're seeking maximum efficiency/regeneration.

For those who don't care, just drive it, the car works well enough that even if you're not hypermiling you'll still get insane economy. Unless of course you drive like a nut case.

 

Using "B" while in EV Mode (not HV) for normal city/rush-hour traffic driving:
More than numbers, what I did constantly back when I was doing the same commute, (and still do occasionally) was to see at which point the EV charge would run out and the ICE would come on, alternating days using either B or D -- and I think all but one time I always reached further when it was in B than when it was in D. Of course, this isn't a lab, and each day has different conditions, but I switched back and forth day after day, and the outcome was almost always that I got further using B than D on the exact same drive, in rush-hour or city traffic (if just going 70mph at night on the freeway, I found no difference between the two in EV. In HV with the ICE on, the mpg would suffer). Maybe it's the way I drive, but for EV-only driving, in city and stop-start driving I found the range almost always lasts longer when in B than in D.

Again, for anyone wondering about this, just try it and see. No harm will be done. If you get better range like me, great. If not, don't bother with the extra work. Whatever the factors are, I wouldn't do it if I didn't see the results.

 

Thanks for the info, but I don't think I can try driving on B as you are suggesting. I never drive in rush-hour or city traffic with a lot of stop and go. My driving is almost exclusively on rural highway at speed between 30-50 mph with very little stops. I have only 3 traffic lights on my 19 miles of commute route.