Braking on Ice .. another hybrid advantage
01-02-18, 12:39 PM
#1
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Thread Starter
Braking on Ice .. another hybrid advantage
Driving today on Texas hwy, came to an overpass ... 1 vehicle was stopped in the middle lane [I was driving in the middle lane] and 4-6 vehicles strewn across both sides of the highway and all pointing in different directions.
My mind quickly keep saying to me, brake and steer. RX started to slow down but I still felt that I was closing in too quickly to the stopped vehicle. I steered in to the slow lane and comfortably kept a wide margin with the stopped vehicle and the vehicle on the embankment. Once past the overpass, I did slow down till the roads appeared dryer and temperature showed 34 (cant trust it fully).
In any case, I started thinking that some of the energy (speed) got sucked up by the regenerative braking. Without the regenerate braking, the actual slow down had to come from wheel to road contact. In ice, it would have been poor (or poorer for sure).
What are your thoughts?
Salim
My mind quickly keep saying to me, brake and steer. RX started to slow down but I still felt that I was closing in too quickly to the stopped vehicle. I steered in to the slow lane and comfortably kept a wide margin with the stopped vehicle and the vehicle on the embankment. Once past the overpass, I did slow down till the roads appeared dryer and temperature showed 34 (cant trust it fully).
In any case, I started thinking that some of the energy (speed) got sucked up by the regenerative braking. Without the regenerate braking, the actual slow down had to come from wheel to road contact. In ice, it would have been poor (or poorer for sure).
What are your thoughts?
Salim
01-02-18, 03:27 PM
#2
No, I don't play soccer!
Salim, I'm glad you got through that unscathed. I haven't really thought about how much energy is sucked up by regenerative braking, probably a bit based on what I see on the instrument panel. But it's honestly the last thing on my mind when roads are icy or snow covered. Instead I rely on a combination of common sense (i.e. bridges and overpasses freeze sooner than road surfaces), releasing the gas pedal at first sign of slipping, staying off the brakes, steering into the direction the vehicle is slipping (not where you want to go), and knowing VDIM will kick in as needed. No doubt that's happened hundreds of times since it's seamless. Getting back to your question, I have a feeling regenerative braking on the 450h has its advantages. Ain't no figure skater though.
01-03-18, 06:03 AM
#3
Racer
When slowing down on ice, it technically doesn't really matter hybrid or not for the most part. Anytime a resistance to forward motion (whether it's regular braking, regen braking, or powertrain resistance) is more than that which air resistance is providing, it involves the contact between the wheels and the road. The regen braking is not removing any resistance the icy road needs to provide, it's simply redirecting the energy that would be dissipated as heat at the brake pads to energy stored in the battery. To reduce the resistance required by the tires while stopping as effectively, you would need to increase air resistance (a drag chute would be a great example).
What regen braking does do, is provide slightly more firm resistance while coasting, perhaps better than the average driver can manage with less risk of a slide / ABS activation. This may be an advantage, but it could also be a disadvantage depending on how slick the ice is and the quality of tires. If it's really slippery, the sudden drag of lifting your foot off the gas pedal may result in skid. This is a scenario that VDIM is supposed to help with.
What regen braking does do, is provide slightly more firm resistance while coasting, perhaps better than the average driver can manage with less risk of a slide / ABS activation. This may be an advantage, but it could also be a disadvantage depending on how slick the ice is and the quality of tires. If it's really slippery, the sudden drag of lifting your foot off the gas pedal may result in skid. This is a scenario that VDIM is supposed to help with.
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Nauticalx (01-08-18)
01-04-18, 08:06 AM
#4
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Thread Starter
Andy, you have raised good points ... that is why I was seeking input.
So the heat loss for normal vs regen is the only difference. The rotating wheel is being slowed down by two different mechanisms while the road/ice contact to the wheel is the same.
Salim
So the heat loss for normal vs regen is the only difference. The rotating wheel is being slowed down by two different mechanisms while the road/ice contact to the wheel is the same.
Salim
01-04-18, 09:00 AM
#5
Not that it helps any, but my first thought at this thread when reading the title was "Keep your diaper on!".
Seriously, though, good thoughts generated by the scenario, Salim. Thanks, too, for your input and perspective, Andy.
The frozen road surface issue is not common where I live, but I do travel to the UP and Maine areas for business in winter time (another week long trip to central Maine coming week after next), so I'm always eager to read these kinds of threads to keep my mind and sense of awareness as sharp and ready as possible because I do drive occasionally in these kinds of conditions.
Seriously, though, good thoughts generated by the scenario, Salim. Thanks, too, for your input and perspective, Andy.
The frozen road surface issue is not common where I live, but I do travel to the UP and Maine areas for business in winter time (another week long trip to central Maine coming week after next), so I'm always eager to read these kinds of threads to keep my mind and sense of awareness as sharp and ready as possible because I do drive occasionally in these kinds of conditions.
01-04-18, 01:57 PM
#6
Right -- hybrid or not has no impact on the traction of your tires on ice. What would have made a difference was having winter tires but they generally aren't all that practical in most parts of Texas.
01-06-18, 05:00 PM
#7
Salim, HSD is set to provide 80% of braking power via regen. Whatever is demand above that, hydraulics kick in.
Suggestion: next time, in case like this, drop it down into B mode. You'll never skid in in it and you have extra engine braking power.
I LUV B mode. totally.
Suggestion: next time, in case like this, drop it down into B mode. You'll never skid in in it and you have extra engine braking power.
I LUV B mode. totally.
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01-08-18, 10:19 AM
#8
When slowing down on ice, it technically doesn't really matter hybrid or not for the most part. Anytime a resistance to forward motion (whether it's regular braking, regen braking, or powertrain resistance) is more than that which air resistance is providing, it involves the contact between the wheels and the road. The regen braking is not removing any resistance the icy road needs to provide, it's simply redirecting the energy that would be dissipated as heat at the brake pads to energy stored in the battery. To reduce the resistance required by the tires while stopping as effectively, you would need to increase air resistance (a drag chute would be a great example).
What regen braking does do, is provide slightly more firm resistance while coasting, perhaps better than the average driver can manage with less risk of a slide / ABS activation. This may be an advantage, but it could also be a disadvantage depending on how slick the ice is and the quality of tires. If it's really slippery, the sudden drag of lifting your foot off the gas pedal may result in skid. This is a scenario that VDIM is supposed to help with.
What regen braking does do, is provide slightly more firm resistance while coasting, perhaps better than the average driver can manage with less risk of a slide / ABS activation. This may be an advantage, but it could also be a disadvantage depending on how slick the ice is and the quality of tires. If it's really slippery, the sudden drag of lifting your foot off the gas pedal may result in skid. This is a scenario that VDIM is supposed to help with.
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