Charging EV portion of the battery going down mountains

Let me rephrase my question: how do you insure that you will arrive at the bottom of your final descent with a full battery yet not waste regen potential ?

 

If you went up the hill in EV only, you will regain about half going down.
But let's say you want to have a full battery at the bottom of the final descent, to use say for city driving. How do you do it ?

 

My solution would be to use our earlier calculation: 1000 ft descent is ~ 6 miles of regen'd range

Example:
Say your last descent is 1500 feet, equal to 9 miles of regen
So start out your trip in EV and switch to HV when 9 miles have been used.

If the Prime lets you follow kWh consumed you could be even more accurate.

 

If my understanding is correct, when you switch to HV mode during driving the car then tries to keep the SoC at the level it is at when the mode change is made. A regular Prius meanders around the 'ideal' battery SOC somewhere in the range of +/- 0.4 kWh so I presume the Prime will let the SoC meander the same, but around the driver designated set point.

 

In my 2012 Prius Plug-in, you don't need to brake, you can just roll down the hill and the battery will charge. If you apply the brakes, apply them gently, so that you stay in the regen range. So of course it depends on the grade, you can coast or brake lightly as needed. Keep the transmission in Drive mode, definitely not Neutral.

Using B mode favors engine braking over regeneration. This is bad! I think Toyota only included B mode because cars need to have a "Low" gear mode with automatic transmissions. The Prius will automatically switch to engine braking if the battery is full, so it's not necessary to use B. Ever. If the Prime is different, please correct me, but I doubt it is.

 

There are at least two good reasons to use B over riding the brakes.

1. So someone behind you can tell the difference between simply controlling your speed down the hill and applying the brakes. Riding the brake pedal is unsafe even if you are just regenerating because your brake lights are on the entire time.
   
2. So you guarantee you don't accidentally push too hard and slip into friction brake mode.

Also, the Prime in Ev mode will not use engine braking in B mode unless the battery is full or it needs to control the battery temperature.

 

Unlike a regular prius, B mode in Plug-in one will actually charge the battery without spinning the ICE. So, less need of using the brake pedal.

Or B mode and using the brakes as required.

 

Yes..it regenerates. Unless it can't.

 

Don't know.

 

With the PiP - No. I suspect same for the Prime.

 

Not according to page 246 and 251 of the owner's manual. It says that B Mode will apply engine braking and will reduce fuel efficiency. It is the opposite of what you want to do.

 

So long as there is room for more regen in the battery I doubt I would ever use B mode.

 

The design philosophy is very simple: if there is a regeneration opportunity, it will be "un-prius" not to capture it.

Manual may be not detailed enough or a left-over from Prius manual.
In reality (and I am speaking of the PiP) - when in EV mode and ICE is stationary, B position will increase regeneration (over just let off pedal in D position) and thus 'imitating' engine brake by more aggressive regen.

See also The one and only Prius Plug-in FAQ! | PriusChat :

Note that the situation in EV mode is a little different, because the engine is not actually running. In this case, the B gear simply uses regenerative braking more aggressively whenever you let your foot off the gas pedal. So, if you prefer to switch back and forth between gears with your hand, instead of switching between the gas and brake pedals with your foot, you can use the B gear.