Synergy drive technical questions...

1. No indicator light, but light to moderate braking doesn't use the brake pads until you drop to 7 MPH.

2. A lot of work was done to make the management software very smart. Even if you have all the bars, the battery is only 80% charged. It doesn't take very long to use a bars worth of energy.

 

Why? Light to moderate braking is more efficient. See this for more.

Effwitt is correct about the 80% level being "full." (Actually I've seen it go as high as 82% after a long descent out of the mountains with continuous regeneration.) Taking it a step further, the car aims for an optimal charge of 60% (six blue bars) to allow just what you suggest -- headroom for any upcoming regeneration.

 

I wish that the standard display on the Prius supported that function but it does not.

I can get a pretty good approximation using my ScanGaugeII. With a cool battery at moderate charge level it will allow you something like 95 amperes of regeneration. If I modulate the braking level a little, and see the regeneration current change, I figure I'm not at maximum yet. This is necessary because the actual maximum value drops with a hotter battery or a higher state of charge.

While some folks posting here would have you believe that you're not likely to exceed the regeneration maximum unless you are braking pretty hard, watching the SG2 has taught me that at higher speeds on downhill it is really quite easy to go past the maximum. 90 amperes of regeneration at 70 mph does not feel like very strong deceleration at all. On the other hand at 25 mph it is quite robust.

 

I had forgotten about this, but in researching something for an unrelated thread I rediscovered this, in case you're at all inclined to a DIY hack.

 

I go down a 12% grade (per state road sign) for 3 miles every workday, at the top I shift the Prius to "B" to help with braking. Half way down the grade when my battery shows full, the motor speeds up like my jeep manual drive when I gear down. Or at least that what it sounds like. What is going on? I suspect that the ICE is doing the braking without regen the battery. I wish that I could not have the battery at 4 or 5 bars at the top of the grade but at 2 bars.

 

That is exactly what is happening. Once the battery is full, regenerative braking no longer has a place to dump all of the generated electricity, so it uses the excess electricity to spin the ICE. The ICE is being used as a big friction device by pumping air with the valves in a high drag configuration.

You deserve some sort of prize for being one of the few Prius drivers to correctly use B mode. This is exactly the application for which it was designed.

You might be a good candidate for an EV switch. That way you might be able to keep your SOC low before you hit the top of the hill.

Tom

 

First, be aware the pads are brought to the rotor as soon as you press lightly on the brake pedal. They are not pressed against it however, just placed in a "ready" position.
So far, the only way anyone has come up with to tell if the braking is friction or not is the DIY circuit posted above.
At slower speeds most reasonable braking is regen. If you panic stop (quick and hard application of pedal) it is purely friction. Be careful, in this situation the car will just about stop on its' nose.

 

Which is great, but too much work for probably 99% of drivers to consider (myself included). Shouldn't there be a signal in the CAN that indicates when there is hydraulic pressure to the friction brake system? If so, it would seem simple enough (for someone who knows what they're doing -- again, not me) to code an XGauge (or whatever CanView uses) to pick up on this and display a simple on/off message. That would be very useful. I try to keep braking regeneration to about 60 amps, but as mentioned above, it's very easy to exceed that at higher speeds. I wonder when I'm seeing 90+ amps if there is also some friction braking being done. I expect there is at times, but it would be nice to know a what point that actually occurs and to be better able to avoid it in future situations.

 

Me too!

If there is, no one has reported finding it, AFAIK. There is a CAN data element for brake pedal position, but of course it tells you nothing about whether a given position engages the friction brakes.

This got me to wondering about the relationship between pedal position and regeneration. I threw together a chart from my CAN-View data and, to avoid straying too far off-topic here, posted it in my CAN-View charts thread.