Why does my 08 Prius use regenerative braking, even when the brake is not pressed ?

It does this to make the car handle in a way consistent with ordinary cars. The slight regen action simulates engine drag. To avoid this, slightly feather the accelerator peddle.

Tom

 

The Toyota engineers have built in several things to make us more comfortable with the car. To make it feel like a "normal" automatic transmission equipped car.
1. Simulated engine drag when coasting. As stated above, just feather the accelerator pedal a bit to shut this off. This takes practice.
2. Transmission "creep" when you release the brake pedal when stopped.
There's a third one but I can't think of it right now. It'll come to me the minute I log off.

 

Like stated above, your best bet is to learn how to lightly apply the gas pedal to kick the system out of regen mode. There are write-ups on how to do this. Maybe do a search for "warp stealth". When traveling downhill or approaching off-ramps this technique is very handy.

You will need to learn how to work with the gas pedal anyway to get maximum milage so you might as well practice now.

Here are some links for ya.

Coasting in neutral

 

If you drive at freeway speeds in neutral you can damage the smaller of the 2 electric motors in your transmission because having the Prius in neutral isn't really neutral but it just cuts electricity flow in the hybrid synergy drive (HSD) transmission. At higher speeds the HSD causes the petrol engine (ICE) to spin over, if this isn't allowed to happen the smaller electric motor (MG1) can overspeed possibly causing damage.

The best way to prevent the over-run regenerative braking is to feather the throttle, easy once practiced and after all when your driving what else do you have to do?

 

At freeway speeds there shouldn't be much braking, unless it's stop and go, in which case it's not really freeway speed. Once you get going fast power is required to overcome aerodynamic drag, so there is almost always some draw from the ICE or battery. That should require you to adjust how much power is supplied, but seldom come off the gas enough to cause regen.

I suspect what you are trying to learn are the same high-mileage techniques used in any car: try to keep a steady speed, avoid slowing down, anticipate, accelerate briskly to speed, etc. In that respect, there is nothing unusual about driving a Prius, except for the constant feedback from the MFD.

Tom

 

Really? I'd like to see some documentation of that. I can't believe that Toyota engineers would engineer in an operating mode in the Prius that would damage the HSD just by pushing a button. I think it's much more likely that neutral just disables engine braking and motor drive, but doesn't prevent MG2 from spinning so that MG1 won't overspeed.
I've got 55,000 miles on my car and I've been coasting down hills at high speeds in neutral whenever I have the chance. No problems yet.

 

Again, where do you get this information from?

 

Sorry, I'm not trying to be a wise guy here.
I know there are overspeed limits on the MG1 and MG2 as well as the PSD, in fact I thought that the top speed that a 3G Prius could run at was about 42 (not 62) MPH before MG2 would need to spin. The only thing I'd like to see some documentation for is the possibility that the Prius will allow either MG to overspeed just by coasting the car downhill in neutral.

 

Thanks Evan

 

just because no fuel is injected does NOT mean that the engine is NOT spinning.


If you have a scangauge, you will see that the engine rpm's are not 0 when you go above 41mph.

 

I did some research to find the answers to that in the Toyota documentation. I posted that information in another thread. I would point to it from here but I don't know how to do that. So I will quote my own post again here:

 

Deleted duplicate post. I don't know how to get rid of the whole reply.

 

I think I read somewhere that at higher speeds, the mg's lack the necessary torque to re-start the engine... Of course, I can't remember exactly where I read it...

 

The following does NOT reflect my assessment of ANY poster here, but with respect to the statement "I can't believe that Toyota engineers would engineer in an operating mode in the Prius that would damage the HSD just by pushing a button", Douglas Adams once said something quite insightful: "A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools."