engine breaking vs. regen braking

If you keep regenerative braking inside the "CHG" on the HIS screen, you are mostly using regenerative braking (ie the friction brakes are not used).

If you go down very long grades, the battery will eventually be full and the car will then need to switch to friction brakes. If you are of this in advance, you can switch "gears" to B-mode as you begin your descent.

B-mode will use the ICE to pump air, slowing down the car, preventing later use of the friction brakes (or at least helping them out).

You need to be aware that as B-mode do so, it discards energy as heat and should therefore be used only in such situations (long descents). Regenerative braking while in D-mode will store more energy in the battery than what B-mode will.

 

It's a car, not a truck. Use "B" mode when descending mountain pass'. You'll find that either in "D" or "B" the battery will quickly fill (to about 80% charge or full according to the screen). At that point you may notice you will have to use the brakes harder. It's -VERY- unlikely you will overheat the brakes. It's a car. I haven't had problems on 18% grade descents over 5-10 km.

 

I like the notion of Jake brakes on a gas-burning sedan. That's essentially what B mode is, isn't it?

 

It depends on how steep the grade, and the speed of the traffic. On mountain highways the grade usually isn't more than 6%, and at highway speed normal drag forces will keep you below the speed limit without braking. If the grade is steeper or the speed lower, use B mode on long mountain downgrades.

Also keep in mind that many people like to use B mode for convenience on mountain downgrades, even when not necessary. That way they can control speed with just the accelerator on all but the steepest hills. Press to go faster, lift to slow down.

Tom

 

It is more comparable to a simple downshift on an ordinary non-hybrid.

 

I just tried this on my way back from San Diego. Those of you who are familiar with the Laguna mountain range know how steep the eastern slopes are. The "B" mode worked just fine and I noticed that when the traction battery was topped off, there was some kind of automatic "bleed-off" of the regenerative power to it. The "crg" icon went blank.
[ame="http://en.wikipedia.org/wiki/Laguna_Mountains"]Laguna Mountains - Wikipedia, the free encyclopedia[/ame]