The other day, I was coming to a stop sign and applied the brakes. Short of the stop sign, there was a patch of gravel. When the Volt hit the patch, it was almost as if the brakes shut off. If I was closer to the stop sign, I might have run right through the stop sign. Is this the ABS kicking in? Seems it would brake instead of providing no braking at all.
Brakes/ABS Off when braking across gravel
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It was probably the regenerative braking system disengaging, what you felt was the loss of regen on slowing the vehicle. This happens when the Volt detects wheel slip. If you had kept slipping while applying the brakes then the ABS would have started to pulse the brakes.
regen/brakes get more wonky/unpredictable when you are going over large bumps or when traction control kicks in.
Basically in situations like that regen isn't something you want to be a factor of any braking, the car is switching to the tried/true/predictable rotors to bring the car back under control.
Basically in situations like that regen isn't something you want to be a factor of any braking, the car is switching to the tried/true/predictable rotors to bring the car back under control.
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If you press the brakes harder, the friction brakes should kick in. I noticed this phenomenon happening more often when my tires were worn, and a new set of tires pretty much eliminated this problem except in extreme conditions. With any other car, you would hear the gravel skidding and possibly ABS kick in, but the volt tries to keep you from sliding, assuming you might have hit a patch of ice or something. But don't worry, the car is operating as designed
You definitely would have been able to get fully braking power by pressing the pedal any harder...it takes a minute for ABS to kick in by itself after a regen dropout though. Regenerative brakes work proportional to wheel speed, so if the wheels slip and suddenly slow way down (as would happen if braking on loose gravel), you get no regenerative brakes.
In this situation, although probably not the safest course of action, wouldn't shifting into neutral be the better method since that will automatically eliminate any regen and force the friction brakes into play? Its a shame that GM doesn't incorporate some sort of programming where if the wipers are on, indicating rainfall, and knowing how regen can create unstable braking on slippery roads, that it automatically just engages friction brakes. I realize efficiency drops in that case, but I'd rather give up on a couple extra EV miles due to regen if it means I avoid an accident due to regen dropping out at a bad time.
Or, you know, you could just let the traction control do what it's designed to do: deal with this kind of thing.
While we are on the subject of wheel slip and regen, is there a consensus on how to approach the following scenario.
I live on a street that starts with an ascent from the main road. When I leave in the morning in my 2017 Volt I usually engage L as I head down the hill at a reasonable 20-25mph, usually I see 7-9kw regen when descending the hill under dry road conditions. This winter I got lucky, we only had one snow fall that needed to be plowed and I waited until the road had been treated, sanded and the sun had melted the rest of the snow and ice on the street before attempting to drive my Volt. I am unsure of the best way of descending this same hill in winter if the road has been plowed and treated but is still covered with packed snow and ice. Other than staying home, my first choice, how should I drive down the hill under these conditions? I have the stock Michelin EnergySaver A/S tires. Should I use L or D? Should I stay off the brakes as much as possible and rely on the regen to slow my descent? I would of course drive slower than I normally would heading down the hill but even at speeds under 10mph I have lost traction when driving other vehicles and braking while descending the hill, ABS kicked in.
I live on a street that starts with an ascent from the main road. When I leave in the morning in my 2017 Volt I usually engage L as I head down the hill at a reasonable 20-25mph, usually I see 7-9kw regen when descending the hill under dry road conditions. This winter I got lucky, we only had one snow fall that needed to be plowed and I waited until the road had been treated, sanded and the sun had melted the rest of the snow and ice on the street before attempting to drive my Volt. I am unsure of the best way of descending this same hill in winter if the road has been plowed and treated but is still covered with packed snow and ice. Other than staying home, my first choice, how should I drive down the hill under these conditions? I have the stock Michelin EnergySaver A/S tires. Should I use L or D? Should I stay off the brakes as much as possible and rely on the regen to slow my descent? I would of course drive slower than I normally would heading down the hill but even at speeds under 10mph I have lost traction when driving other vehicles and braking while descending the hill, ABS kicked in.
I believe the owners manual suggests D when slippery conditions may be present. Since I don't know enough about how the system transits between regen, blended braking and full friction braking nor the reaction time it takes for the system to determine which is the best course of action I would suggest sticking with the recommended D and driving normal and relying on the ABS, and traction control systems to do their thing.
Please provide a page number for the Owner's Manual where it suggests D when slippery conditions may be present. What I found is a warning dialogue box on page 169 of the 2017 Owner's Manual that states to always have the vehicle running and in gear (preferably low range) when going downhill. On page 170 under Loss of Control - Skidding there is a bullet statement "Try and avoid sudden steering, acceleration, or braking including reducing vehicle speed by shifting to a low gear or by using Regen on Demand. Any sudden changes could cause the tires to slip" but nothing about setting out, continuing to drive using L. Also, there is nothing in the winter driving section that starts on page 170 cautioning about driving using L or D, only to turn off cruise control.
It seems like GM is dodging this one, leaving Volt drivers to figure this out for ourselves.
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In practice, I drive in D all the time except when the streets are snow/ice packed. During Snowageddons 1 and 2, I did lots of experimentation and L does a lot to help slow the car and not lose control, where D and tapping on the brakes caused lots of anti-brake locking (ABS kicked in, car kept rolling)
It won't matter, so long as the traction control stuff is on, and your foot is ready to press the brake pedal. The only thing not to do is be reflexively depending on regen to slow you rather than ready to apply friction brakes if needed. Because if the wheels do slip, that regen is turning off for a few seconds and that'll make you speed up and have to brake even harder to haul back the velocity, which makes it even more likely that the ABS/traction control will fire, and off goes the regen again.
Which is why I don't make it a routine habit of just driving around in L. I don't want to get too used to it being there as part of my "how I drive" patterns. Popping it on in heavy traffic (which is already not-normal driving) or in combination with old-style cruise control (where maintaining a constant speed is the expectation and pressing the brake is turning that off anyway) doesn't affect my instincts in the same way. Your experience my vary, but that's been working well for me.
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