I hit a situation where I think the cruise control can help --

First some intro: I'm driving a Lexus RX (actually, wif lets me drive it once in a while, 'specially if it needs gas,) which has a 'power-required' gauge, which shows margins for regen-braking saturated, regen vs. battery discharge, and when the batteries are about to be supplemented with engine power. Do other models have a gauge like that? I'm not talking about the engine/motor/battery/wheel schematic, but a gauge with different markings as the needle swings around. I can anticipate when the engine will re-light by watching this gauge.

Also, I thought I read in another thread that the Highlander runs the engine whenever the vehicle is rolling faster than 42 miles per hour, is that true? If so, that's different than the Lexus and changes my cruise-ctrl story. Anyway...

On I-5 North, coming into the Portland area, there's a straight, level to slight downgrade, with the speed limit dropping from 65 to 55. I find that if I hit that segment with the cruise control locked in at 68-70 (same speed as everyone else) I can start using the 'bump-down' function to reduce my set speed by 1-2 miles per hour. Maybe give it two bumps initially. The engine kicks off and I'm motoring along on batteries.

Watching the power-required gauge creep up as I approach my set speed, I can see when it's about to relight the engine. Give the cruise-ctrl another bump down, and the power-required gauge drops back. As I approach the new speed, the gauge creeps back up and I give it another bump.

What I'm doing is maximizing the draw from the batteries to keep up as much speed as I can and using the gauge to cleanly avoid engine relights, while slowly decelerating since the motors can't maintain 65-68 on this grade. On this segment of I-5 I can maintain highway speed, decelerating from 68 down to 58 over a span of 4-5 miles, all-electric. I don't think it's a generally applicable technique, but it seemed to work in this set of circumstances. Yes, I could do it with my foot, too, but this felt like it was easier to be smooth at.

* With the gauge, it's easy to see the amount of braking actually available due to the motor regenerative braking. I don't know if it's limited by what the motors-cum-generators can put out or what the battery can accept, but it's not as much as you might think. To maximize power stored, especially from highway speed, anticipate your slowing, and get on the brakes lightly, early. Maximize the time you're stuffing power back into the battery.

* Another thing that caught my attention how well the RX coasts. On another segment of I-5 with a mild downgrade, maybe 2-3%, I was going 70 with foot off the gas (mild regen) and was still gaining speed. That car really likes to roll...

Benton 6may08