If you have a loooooooooooooong steep enough downhill and since in L, it'd be a sloooooooow drive also, then I guess it's possible.

 

Slow? There's a mountain pass here that will add 4-5 bars in 20 minutes with the cruise control set to 80 MPH. If the grade was twice as long then a full charge might be possible.

 

Driving over the Catskill mountains, I was in hold mode on the way up. had about 10 miles left in the battery.. On the way down, I put it back in normal mode and coasted all the way down. In the winter, heater on, at night. Gained 16 miles worth of charge by the time we were out of the hills. I popped it in and out of hold mode every so often to lock in the gain on the traction battery. It was a cool science experiment. So can the car charge at a rate higher than 3.3? Yes. Why it doesn't allow for wall charging at a higher rate? GM could tell you. Safety? Cost of equipment?

Nice gains from my downhill ride and a whole lot faster than charging from the wall at 110 or 220. There are a few other posts out there that explore this concept. Between resistance losses and friction losses, not to mention the cost of a serious set of rollers, and wear and tear on them and the car, I suspect that your rollers are at a net deficit compared to just plugging in.

 

If you exceed the cooling capacity of the battery system, be aware that once a Li battery ignites, it normally burns to the ground. When a car is moving, it has a lot of airflow for cooling purposes. Normal industrial fans will not match 50 mph airflow. I know this from dyno testing cars.

I imagine the GM electronics will stop that from happening and kick off the regen before the heat exceeds safe limits.

 

Putting the loser economics of such a scheme aside, the big unknown is whether the car can sustain a continuous recharge at that high of a rate. What works for short duration may be a battery killer under longer application.

 

Regen and accel are limited to 10s bursts - it will drop to a sustainable level after that.

I forget the sustained number, but it was in the slides about battery data between the different gens a few months back. It is significantly less.

 

It can recharge faster with regen than the charger because the regen is already DC. No AC to DC conversion required. But the DC recharging is probably limited to 1C which is still 16.5 kW, or more, depending on the battery.

 

Test could be done by running the battery all the way down. Towing it with another car so all wheels are on the ground. Turn the car on and put it in "L." Should be able to get 50kWH or more over an hour on highway at 55. May need much less time if it works.

Why not have Volt 1, running on battery power, tow Volt 2 in "L" until Volt 2's battery is fully recharged via braking regeneration, then reverse order and Volt 2 can run on recharged battery power while towing Volt 1 in "L" until Volt 1's battery is fully recharged, then switch again... should be able to drive the two Volts coast to coast on braking-regeneration-created-battery-power perpetual motion only, right?

 

You might have something there! But I would use two Volt 2s

 

I noticed on "L" the brakes can make 50 kWH easily but just for a few seconds as the car slows down. This charges the battery at 50 kWH and then varying levels as the car brakes and slows on a trip.

For clarity, charging power is expressed in kW, not kWh.

kWh is a measure of how much energy a battery will store. For example, the battery in a 2016 Volt stores 18.4 kWh of energy.

In other words: Energy = Power x Time (kWh = kW x hours)

Think of it this way: If a person asks you "How much energy does a 100 watt light bulb use?", in order to answer, you would need to know how much they actually use that 100 watt bulb. If the bulb is never turned on, it uses no energy. If the bulb is used constantly, it would consume 100 Wh of energy for each hour, or 2.4 kWh per day, or 72 kWh per month, or 876 kWh per year.

So serious replies. Could this work? Break the 3.3 KWH barrier for charging?

Yes. The Volt's battery pack can charge much faster that 3.6 kW. Regenerative braking is a good example of this.

The 3.6 kW charging limitation is due to the on-board charger that converts AC to DC and steps up the voltage to over 400 volts DC. In the 2016 Volt, I've heard the charger is in the rear by the 12-volt battery. In earlier models, the on-board charger is inside the front fender on the driver's side.

The on-board charger is basically a large power supply. To double the charging rate you would need double the power supply, which means increased cost, size, and weight. The larger power supply would also give off a lot more heat, which may actually affect the design of the car.

In any case, with the Volt's range extender, 3.6 kW is plenty. With a pure BEV, a slower charger can acually prevent you from getting somewhere on time. With the Volt, the range extender makes that a non-issue.

 

Break the 3.3 KWH barrier for charging?

Actually, one can already "fast charge" one’s Volt. With battery fully depleted and car parked, turn the car on and switch to Mountain Mode. In a Gen 1 Volt, the ICE will start up, run for ~15 minutes using ~0.36 gallons of gas, and then shut off after recharging the battery to the MM-maintained soc level, ~4 bars (this procedure is shown in the Selfcharging Volt video that uses a 2012 Volt). Gen 2 owner feedback indicates their MM-maintained buffer is only ~2 bars, which should take less time and use less gas.

The creator of the video estimated that if GM allowed us to use MM to fully recharge the 2012 Volt battery, it could be done in ~40 minutes using ~1 gallon of gas. Clearly it is much cheaper in most areas to use 12-13kWh of grid electricity than 1 gallon of gas to recharge the battery.

Note that if your all-electric range is ~40 ev miles, the ~1 gallon of gas it would take to fully recharge your battery is about the same amount of gas burned by the ICE to move your Volt ~40 miles down the road.

Not sure if your envisioned "roller platform" could safely recharge the battery via braking regeneration in the same time frame or less (MM recharging can be done while driving for those who are concerned with heat dissipation), nor if the cost to power the rollers would exceed the cost of the normal battery recharge.

Why doesn’t GM configure the Volt to allow full recharging via MM? Because there’s no practical use for it in most situations when recharging at home with grid electricity is usually so much cheaper. On a long-distance trip the Volt battery does not hold enough driving distance in that full battery charge to justify a lengthy refueling stop. Range vs power consumption graphs suggest that the Gen 1 Volt’s all-electric warm weather range shrinks from ~50 ev miles at 40 mph to ~30 ev miles at 75 mph. A roller-platform- or MM-fully-recharged battery would thus give you only 30 miles of freeway-speed driving. Why would you want to make a recharging stop every 30 miles on long trips when normal ICE operation allows you to drive non-stop for hundreds of miles?