[cougsfan]

Today I discovered something unexpected. Not a big problem, but one that caught me a little off guard. I left my house with a full charge on the battery. Out of my house the first 1-1/2 mile road is all down hill with a 400 ft total drop, with a steep downhill at the very end to a stop sign. As it was cold out (25 F), and I had over 50 miles to drive, I thought it might be best to start out in "hold" mode to warm the engine coolant up a bit.

As I got to the steepest part of the hill at the bottom of our road, I hit the regen paddle on the wheel to slow down. (I am training myself to stop this way) Nothing happened. I continued to gain speed! Apparently if the battery has as much juice as it can stand, regen braking just doesn't happen. Never tried low gear, but my guess it wouldn't have slowed me down either. Good thing it has hydraulic brakes. Stopping was a bit abrupt but not that big of deal. (Good thing the snow melted this weekend!) I guess all this makes sense, but it certainly did catch me by surprise.

Switched back to "normal" mode and a few miles down the road and everything worked fine again.

 

[Upper5Percent]

http://gm-volt.com/forum/archive/index.php/t-15197.html

last post of the thread...
saghost 07-17-2012, 06:10 PM
jaksecret's post <Me too, 7400 feet to about 5300 feet every day in about 7 miles. car starts full at 44 miles, increases as I go downhill to 50 miles, then near the bottom of the hill, i lose the deceleration of regen and the car feels like its coasting. I don't know that it dumps that power to ground, I think it just stops regen mode.>

Put it in neutral after you think it's coasting, and you'll see. The power dump isn't nearly as strong as L usually is, but it's definitely there...

 

[caskConditionedAle]

To me, this just provides more reasons to ignore the paddle. The brake can provide identical regen as the paddle and in addition, includes the ability to seamlessly modulate to friction braking when needed.

 

[UncleDon]

I am definitly under the impression (from reading in this forum) that the brake pedal does not "blend in" regen. When braking, since the foot is off the go pedal, regen occurs immediately but regen does not increase as brake pedal pressure increases. I thought initial light braking engages friction braking lightly immediately and friction braking increases as brake pedal pressure increases. Am I wrong? I am only 2 months into my 2018 Volt ownership so I am not an expert.

 

[PrivatePilot]

I am definitly under the impression (from reading in this forum) that the brake pedal does not "blend in" regen. When braking, since the foot is off the go pedal, regen occurs immediately but regen does not increase as brake pedal pressure increases. I thought initial light braking engages friction braking lightly immediately and friction braking increases as brake pedal pressure increases. Am I wrong? I am only 2 months into my 2018 Volt ownership so I am not an expert.

No friction braking occurs on the Volt until the ability of regen to maintain the commanded deceleration rate is exhausted. Paddle or pedal is irrelevant.

If you download the "MyGreenVolt" Android APP and interface with the car you can set it up to let off a loud "Bong!" whenever friction brakes come into play, and except for the last few feet, given non-aggressive braking, regen is doing 100% of the work.

As for lack of regen due to the SOC being at 100%, that's normal - there's nowhere for the power to go so the car reverts to friction braking and disables regen until such time as there is.

On the Bolt there's actually a programable option called "hill top reserve" which will stop the car from charging to 100% for people who live in areas where the beginning of every trip is downhill - there's room left in the battery for the regen that would otherwise be lost to friction brake heat.

 

[pr11576]

If you watch the power generated in the display while breaking with the foot pedal, you can see that if you brake harder, more energy is generated until the car slows down and there is less energy to capture.

 

[cougsfan]

No friction braking occurs on the Volt until the ability of regen to maintain the commanded deceleration rate is exhausted. Paddle or pedal is irrelevant.

If that is true, why even have the paddle? I have no way to prove this, but it always seems that the regen number is higher when using the paddle over the pedal under seemingly equal stops. Maybe because the paddle often makes me stop faster than I normally would.

One thing I don't like about the paddle is it doesn't modulate the stopping power nearly as well as the brake pedal does. You have to guess when to apply the paddle. And if one applies the paddle do it too early, you then have to constantly release/ re-apply to stop in a linear fashion in the distance available.

A funny side note. I drove my pick-up today for the first time in weeks. If found myself slapping the steering wheel with my left fingers every time I had to stop.

 

[PrivatePilot]

If that is true, why even have the paddle?

For the same reason the Gen1 has a "L" mode that allows one pedal driving - because some like it.

But in the end the brake pedal itself will do the same thing. Push the pedal hard enough and it'll produce the exact same amount of regen as the paddles before resorting to friction brakes.

The only advantage of the paddles is that you know that you are using ONLY regen for deceleration, as opposed to the pedal where the blend line between regen and friction is sometimes hard to pickup on. There is merit in that, all things said.

 

[wordptom]

Your experience is familiar to those Volt/Bolt owners who live at the top of a hill and start their day with a long downhill drive.

GM engineered the cars to prevent the battery from charging to full capacity or discharging completely to provide better battery longevity (Wikipedia says the Gen 1 Volt has a 65% usable SOC window, the Gen 2's is a bit larger). After charging is completed, the battery still has a small buffer above the "full" state of charge level that can receive a charge, allowing regenerative braking to still work when you first unplug and drive off. If you then immediately start downhill, regen may quickly fill this buffer. Regenerative braking can no longer "recharge" the battery, so is no longer available.

L and D are not "gears," but different levels of regeneration. Once the regen filled the battery’s buffer and the SOC was at the maximum allowed, neither one (nor the paddle) would have provided braking power. (The Bolt has a "hilltop charging" setting that stops the charging at less than "full charge" for those who have this problem).

Regenerative braking occurs in both Normal and Hold (or Fully Depleted) Mode, and use of that regen counts as Electric or Gas miles depending on which mode you were in when it was obtained. Note that when you start downhill with a nearly full battery in Normal, once regen is no longer available, you’re neither using grid battery power nor putting regen back into the battery, so you no longer meet the criteria of "Electric Mode" driving, and as you continue downhill, the distances may be recorded as Gas Miles.

Oddly enough, perhaps if you had chosen to blast out electric heat in Normal mode instead of using Hold to access gas engine-based heat, the electric heater’s power consumption might have drawn enough from the battery to keep the buffer from filling, allowing you reach the bottom with regenerative braking still available. As you noted, switching back to Normal ended Hold Mode’s attempt to "hold" the battery’s state of charge, and the subsequent use of electric power soon enabled you to regain use of regenerative braking.

 

[ACER]

Quote: "Apparently if the battery has as much juice as it can stand, regen braking just doesn't happen."

Can anyone confirm this? We have a 2016 purchased new and we love it. It is our only car and for the majority of our driving we are using electric-only. The only time we use petroleum is during an occasional out-of-town trip and our 30,000 miles lifetime MPGE is approximately 81.Whenever the car is in our driveway it's attached to its charging station so we almost always leave home with a fully-charged battery. The first half mile from our home includes a couple of mild-to-moderate downgrades. The paddle regen doesn't seem to work for these and this is the only time that happens. If the above quote is correct that answers our concern.
Thanks

 

[jcanoe]

Quote: "Apparently if the battery has as much juice as it can stand, regen braking just doesn't happen."

Can anyone confirm this? We have a 2016 purchased new and we love it. It is our only car and for the majority of our driving we are using electric-only. The only time we use petroleum is during an occasional out-of-town trip and our 30,000 miles lifetime MPGE is approximately 81.Whenever the car is in our driveway it's attached to its charging station so we almost always leave home with a fully-charged battery. The first half mile from our home includes a couple of mild-to-moderate downgrades. The paddle regen doesn't seem to work for these and this is the only time that happens. If the above quote is correct that answers our concern.
Thanks

That is correct. When the Volt's battery is near 100% SOC the Volt will automatically limit the amount of regen that is available. Use the foot regen pedal (brake pedal) and you will not notice this at all.

 

[ACER]

Thanks jcanoe. That removes one of the very few concerns/reservations we have about our Volt.