How to Efficiently Drive a Prius

It is true that the battery charges in B mode, you just won't get as much charge as you will in Drive. However, if you are going down a long, steep hill, B is helpful because you don't need all of the charge you would get in Drive.

You don't use your brake pads when gently braking until you get to 7 miles per hour. The regenerative braking system charges the battery instead.

Coasting is better than braking, but it is best to glide when possible. Don't worry about the charge on the battery. The car won't let the battery charge go too low.

 

The possibly non-intuitive thing here is that for best fuel economy you want to use the brakes *and the battery* as little as possible. All energy conversions unavoidably waste some energy as heat, and going into and out of batteries is especially bad.

 

This is one of the most complete writeups on pulse and glide.

As for efficient acceleration, I'm not fond of subjective terms like "brisk," "modest," or "gentle." What's modest for one person could be either brisk or gentle for another. Instead, take a look at this for an objective criterion.

 

When I pulse, I use the engine and the battery to get back to 40 rather quickly. At any rate, you don't have to worry about over charging the battery, the car won't let that happen. In fact my car HV battery has somewhat diminished capacity from use. I fairly often get up to 8 green bars on the battery gauge. When I stop, the HV battery spins the engine without using fuel to remove any excess charge.

Regards,
Dave

 

That's pretty much it. You can adjust your high and low speeds and range as traffic, road conditions, and your own tolerance for going more slowly allow. You'll get respectable results at just about any speed range below 41 MPH, though the slower the better.

Dave is correct that the car won't allow overcharging. The car manages state of charge (SOC) very well on its own.

See my link on efficient acceleration. If you keep instantaneous MPG at least half the vehicle speed during ICE-on conditions, you'll keep the ICE within efficient ranges and avoid pulling from the battery. The car will decide for itself, based on SOC, how much energy to send to the battery.

It might seem counterintuitive that hypermilers generally avoid using the battery. All energy ultimately comes from the ICE. Best is to use that energy immediately for propulsion. Losses occur when energy is converted from one form to another, which is what happens when it is diverted into the battery and then back out when used.