Rookie Question:"B" Drive

To answer your question, you can switch back into D mode 'on the go' with no danger at all.

To answer your question you didn't ask...There is little need to use B mode. The only time it is really of any potential benefit is for very long steep downhill grades. Almost any other use will result in reduced gas mileage and a lot of confusion when the car starts acting weird if you forget to put it back into drive.

I've had my car over 2 years, I played around with B mode in a lot of different circumstances, and can now count on one hand the number of times I've used it in the last 6 months.

You've got lots of other things to learn about making your Prius work the best for you...don't worry about that B mode at all until you've mastered those--it's almost completely useless.

 

NO it will not help charge the battery more.
Yes I know how to charge the battery to the max. But I won't tell you for fear you'll do it--the process is wasteful as it converts gas to electricity with inherent additional losses. You car is programmed specifically to resist charging the battery full (in fact it never can, the 'full' on your display is actually only 80% maximum charge on the battery). This helps preserve the life of the battery and maintains an area to hold more charge should the need arise.

You will, eventually, see a full 8 green bars...probably this winter as the car maintains a higher average SOC in the cold weather. Of if you don't have winter where you are then you'll see it one day when you have to use the brakes going down a long hill behind another car.

You can then be excited that you saw it and quit worrying about it. Trust your car is doing the best thing for you and for itself.

 

I'm afraid "Mr. Prius" doesn't know what he's talking about. Tapping the B twice doesn't change it's "charging" rate or efficiency.

And no one claimed that using B-mode doesn't allow charging of the battery when used. The point is that it doesn't charge the battery at any faster rate than braking. To further the point there is no benefit to intentionally trying to charge the battery. Charging the battery is done as a means of recapturing energy that would otherwise have been wasted--be that as heat from friction when braking or heat/unburned fuel from the ICE, or whatever.

Charging the battery should never be a 'goal' to achieve. Having a high charge on the battery is not a good thing (nor is it a bad thing), but when you are doing more braking than necessary (ie seeing a lot of regen cars on the consumption screen) that is proof of inefficient driving--you're braking too much. Your goal should be to see as few regen cars as possible. This is because you can only recapture a small percentage of the energy used to get you up to speed, it is better to conserve and use that kinetic energy as much as possible by coasting/gliding to stops rather than running up to stops and braking hard, to maximize regenerative braking when you must stop, but to try to avoid coming to complete stops when practical as well.

That loud reving you hear when the battery is topped of is energy being wasted. The ICE spins to slow the car b/c the battery can't take any more charge. Any braking is being done by the ICE and friction brakes....that is one of the main reasons for not letting your battery charge into the green.

 

mjapplewood,
Not that my 3800 posts on this forum alone and 2 1/2 years of studying all things Prius or my lifetime 52.5mpg over 31k miles or the multitude of articles I've read mean anything, but you are under some serious misconceptions about how your Prius works and why it does the things it does.

Fact: You can actually regenerate MORE by manual braking (about 60amp) than with B-mode(closer to 50 amp)--this has been measured and proven as a fact.

Fact: When your ICE spins up that's a bad thing--you're burning gas to drain the battery which does not want to be charged into the green.

Fact:B-mode is relatively inefficent b/c of the second fact above. RPMs zip into the range of ~2500 rpm and higher once the battery nears a fuller charge.

Fact: Any time power is converted from one form to another there are inherent losses. Thus when you step on the brakes to regen (or use B-mode which essentially does the same thing) that power must be converted, via the Inverter, to be stored in the battery and a certain portion of that energy is lost in that conversion. When you want to reuse that energy to power the car or start the ICE or charge the 12v battery it must again go through the inverter and you again suffer some finite power loss. Having regenerative braking is clearly better than not having it, but it is still inefficient any time you have to slow down.

Fact: B-mode is not designed as a means to charge your batter or as a means for routine slowing/braking. It is designed to use the ICE in combination with the regenerative braking to help keep the speed of the car down on very long downhill grades. The same thing can be accomplished just using the brakes, but one's foot/leg tires after several miles.