What is B Mode for?

Coming down super long downgrades, where there's a danger of fully charging the battery, long before the bottom of the hill.

Using B will delay the fully charged condition, and reduce the time the car has to rely on friction brakes only, possibly overheating.

Other'n that I would leave it in D, all the time, use the brakes as needed.

 

I would add we don't have a lot of metrics for the PiP which uses LiON batteries. Certainly the NiMH equipped Prius suffered from 'heat pumping' where descending would charge and heat the batteries. We just don't have similar data for the LiON.

Bob Wilson

 

Completely missed that OP has a Plug-In. B mode application is somewhat different in that case?

 

That happens when the thread is in the wrong forum. (Gen 3 vs Gen 1 Plug-In)

 

"B" mode use still applies even though it's a PIP.
Because the Prius will "take off" down steep grades (very low drivetrain friction/loss) you can use "B" to help control the speed without excessive use of the brakes. Note that cruise probably won't work in "B" mode, though I forget the details (hardly ever use "B" as it's "wasteful").
The "save energy" and "control battery temp" part is for us fanatics. In truth the car will take care of itself just fine.

 

It takes a very long hill to fill the PIP battery, 3000 foot vertical drop vs 600 ft in a Prius.

 

Yes️ I notice coming down a 4000ft grade at 3000 the battery is full at this point and down hill speed goes above 80mph I shift to B mode instead of using the breaks.


iPhone ?

 

It sprouts special grip tires for traction over any kind of terrain. At the same time, 5,000 horsepower is distributed evenly to all four wheels.

 

It is only the wrong forum because we would give you the wrong answer. A 'normal Gen 3 fills the battery during a 600 foot vertical downhill. The Prius PHV takes over a 2000 vertical drop, so B is much less likely to be needed.

 

During model years 2012-2015, the PiP group here actually was a subforum under Gen3. Only when the 2016s came out and the different models moved out generational sync did the PrisuChat architects move the PiP off separately, no longer a GenX subforum.

 

I have only used B-mode once in my PiP, and that was coming down from Yosemite after the battery fully recharged and the grade was still very steep.

If you know you will be descending a very long and steep grade, use your EV range up to deplete your battery before beginning the descent. This will give you the most regen capacity, save some brake wear, and improve your MPG.

I would say it usually takes 4,000 feet of elevation drop to charge an empty PiP battery. The last couple miles are slow to regen since charging tapers off near the end. You will notice the engine comes on periodically on extended downgrades for what appears to be no reason. Whenever the EV light turns off, you know the engine has turned on. B-mode always turns the engine on.

 

…ah, the "B-mode" - I seldom use it, however I have been known to employ it to slow down without giving the game away to a persistent tail-gater (…i.e. slowing down without using the brakes (…and brake-lights! )), but treating the would-be butt-sniffer to a laundry-experience they so rightly deserve! (BACK-OFF, and please change yer underwear when you get home!!! (…pheeeewwwwww!!!)

 

Well, congratulations on buying a decent car, and getting rid of the junk! …and welcome to PriusChat! I've found one of the least mentioned, but most useful uses of the "B" mode is to give any would-be tailgater a well deserved LaundryExperience of the first order in the event of me not being able to see their front registration-plate in the rear-view mirror! (…think of it as the opposite of flicking on the marker lights to simulate brake-lights - think "Eiger Sanction (1975) (Clint Eastwood)" (…the chase scene in the desert?) It is also curious as to how often I'll attract a tailgater just before my windshields (both front & rear) need a good wash!

 

I really used B mode for the first time last weekend in NC. Coming down the mountain, I didn't want to put all the strain on the brakes, so I used B mode to scrub off a good bit of downhill roll in a couple of places.

 

This is no different than any traditional car. All of them can be downshifted. And nearly all of them have larger engines that enable slowing down more sharply than a Prius will.