Does anyone know or know how to find out "what percent of a Toyota HSD vehicle's total electricity and/or battery charge comes from brake regen" and what percentage comes from the gasoline engine charging the battery "on the side"?

I'm just wondering how much energy is really recaptured.

Has this been talked about before? If so, please just point me to a thread.

Thanks to all !!

In my case I'd say less than 5%

Efficient drivers do it better.
1003 miles a tank personal record. 74MPG calculated. HCH1 CVT

I have wondered the same thing.Just how much energy is actually being recaptured while braking with the brake pedal.A lot of the "braking" energy is actually being seemlessly "stolen" every time you get off the gas and glide without actually braking.The display seems to indicate that it is adding a bit of regen braking even though I'm not telling the Prius to brake.
I would guess actual braking + this sneaky braking might be more like 10-15% of the battery energy used in city driving(much much less hy of course).I think regen can be as much as 200 watt hr/5 minutes.200 watt hrs is about enough to move a Prius about 1 mile at 25mph.If on average you got just 66 watt hr per 5 minutes(1/3 of max)-you would be getting about 4 "free" 25 mph miles every hour.This is about 10 minutes of steady 25mph driving; it might be 30-40 seconds of hard acceleration.
I'm just guessing, but I think 10-15%.If it is a lot less than 10% it wouldn't be worth the effort/weight/cost. Luck,Charlie
PS This 10-15% includes that sneaky unasked for braking the control unit does for you everytime you get off the gas pedal.
PPS Does anyone know just how much electrical energy is used during an average hour of city driving?

Like all things Prius, it depends on how you drive the car. If you're doing pulse & glide at low speeds, and pulsing correctly, the ICE won't charge the battery much at all. If you drive a lot of highway miles, the ICE will charge the battery a lot.

The instrumentation on regenerative energy is limited to 'yellow triangles' showing 50 Wh and half triangles of something less. As you drive, the 'yellow triangles' are added to the 5 minute summaries. Of course, they are a function of how you drive and the road conditions. For example, driving I-540 through the Ozark mountains of western Arkensaw, regenerative triangles are impossible to avoid. But later, on the Mississippi flood plains using cruise control to follow a truck, I drove hours without a single triangle.

As for how how much energy is saved, most of our Prius brakes last two to three time longer than on a gas only car. If we can find out how much energy it takes to 'wear out' a set of brakes, the energy saved can be easily calculated. So far, I've not found a report on how much energy it takes to wear out brake shoes.

GOOD LUCK!

Bob Wilson

Operation Iraqi Oil Freedom:

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My other 1500 cc car:

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The classic Prius HV battery has "room" for about 700 watt hours of energy between the SOC limits, or 14 regen symbols. With additional instrumentation to observe SOC status, I found that descending a 1000-foot hill could fill 'er up. This could be compared to an E = m*g*h calculation. Something like 20% of the potential energy of a road descent can get into the battery, but I would not want to claim this as an "official" Prius number. Wind energy loss varies dramatically with speed, if the battery is too warm it will not accept charging at a high rate, etc. etc.

DAS

Thanks Doug,

This is from a minimum SOC, ~40%, to maximum, ~80%? I understand the Prius normally likes to keep the SOC at 60%.

My understanding is a gallon of gas has about 37,000 watt hours of energy. Given a 30% ICE efficiency, a gallon would yield about 12,000 watt hours. But unlike the gallon of gas, the regen energy happens over and over and over again.

Although regen is not 100% efficienct, it is 'free' for the taking. It is enough to give our brake shoes unusually long life . . . a good thing.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.