Volt does not recharge its batteries while driving...

[spwolf]

HA!

GM clarifies the role of the Volt's 1.4-liter engine, and the fact that it cannot be used to return the car to "electric-only" drive mode.

Once the Volt's 40-mile battery charge is depleted, the car must be plugged in before electric-only mode can be used.

No "Revolting" the Volt: Chevy Battery Does Not Recharge While Driving


So how does that happen? That means that when out of electricity, Volt will get substantially worse mileage than other hybrids or even high mileage cars as it will have additional weight that those other cars with 1.4l engines dont have.

[Jack66]

What happens to the MPG when the small engine has to move the car and "sustain" the battery charge? That can't be good.

[San_Carlos_Jeff]

Makes sense to me. Once the battery is depleted the most efficient way to move the car would be to have the engine generate only the juice needed. Using the engine to charge the battery is a lot less efficient than waiting for the grid power. This would only come into effect after 40 (claimed) miles so for most drivers and most usage it wouldn't matter. In my case I commute 46 miles a day so for 6 miles the engine would fire up and then when I got home the grid would do all recharging, thus minimizing gas used.

[miscrms]

Despite the hype, this is what many have believed for some time. Its not exactly shocking, this is how most plug in hybrids operate. Just one more way thtat the volt is just another hybrid, not a "range extended electric vehicle." Charge sustain mode is the classic term for the mode a pluggable hybrid runs in once its battery is depleted. In that mode it may either use the battery a little to aid in high power demand situations, then replenish back to the sustaining value (as the prius does), or it may just not really use the battery at all at that point.

While it sounds bad, this is probably just as well. In order to offset as much gasoline as possible you generally want to end the day with the battery as low as possible. That way you have as much room in the battery to fill from the grid as possible. Any gas spent charging the battery would in that sense be a waste. The rub is that the ICE may be able to run more efficiently at cruising speeds if more heavily loaded. Charging up the battery is a great way to take advantage of that fact. This is one reason some folks are looking at adding a lot more smarts to PHEV systems. By using the NAV system, and either knowing (from user input) or predicting (from past driving experience) your driving route the car would try to balance these too situations. It would recharge the battery just enough to make sure you still end up at home with an empty battery, but would operate the ICE at higher efficiency as much as possible reducing overall fuel consumption.

Rob

[spwolf]

Originally Posted by miscrms

Despite the hype, this is what many have believed for some time. Its not exactly shocking, this is how most plug in hybrids operate. Just one more way thtat the volt is just another hybrid, not a "range extended electric vehicle." Charge sustain mode is the classic term for the mode a pluggable hybrid runs in once its battery is depleted. In that mode it may either use the battery a little to aid in high power demand situations, then replenish back to the sustaining value (as the prius does), or it may just not really use the battery at all at that point.

While it sounds bad, this is probably just as well. In order to offset as much gasoline as possible you generally want to end the day with the battery as low as possible. That way you have as much room in the battery to fill from the grid as possible. Any gas spent charging the battery would in that sense be a waste. The rub is that the ICE may be able to run more efficiently at cruising speeds if more heavily loaded. Charging up the battery is a great way to take advantage of that fact. This is one reason some folks are looking at adding a lot more smarts to PHEV systems. By using the NAV system, and either knowing (from user input) or predicting (from past driving experience) your driving route the car would try to balance these too situations. It would recharge the battery just enough to make sure you still end up at home with an empty battery, but would operate the ICE at higher efficiency as much as possible reducing overall fuel consumption.

Rob

hm.

If it does what Prius do - both recharge battery via ICE up to certain level and recoup energy from braking, wouldnt it then be possible for it to go into electric mode again even without plugging it to grid? Just not for 40 miles of course.

Article suggest that once out of electricity, your ice will power the car 100% - ie car will not go into electric only mode anymore...

[miscrms]

Originally Posted by spwolf

hm.

If it does what Prius do - both recharge battery via ICE up to certain level and recoup energy from braking, wouldnt it then be possible for it to go into electric mode again even without plugging it to grid? Just not for 40 miles of course.

Article suggest that once out of electricity, your ice will power the car 100% - ie car will not go into electric only mode anymore...

I think that is correct. It will not go into electric mode anymore. What it may do is use a little power from the battery to give you a little boost during acceleration for example, then either put it back with a bit of extra juice from the generator during cruising, or from regen. Since the ICE/generator is much less powerful than the battery, if they don't do this the car will be much slower once the battery is depleted. I can't think of any reason they wouldn't do this as the amount of energy required will be trivial compared to the size of the battery. On the other hand it does complicate the battery management system significantly, and they are trying to rush this thing out the door. A good hard acceleration probably wouldn't even take 1% off the SOC. If I had to guess I'd expect they will run charge sustain mode kind of like the Prius does. They'll hold at 30%, but allow it to drop to 28% or so during assisted accelerations or small hills, and allow it up to 32% or something to allow for regen. This will be of no good on something like a long hill climb though. Then you will really be stuck with what the ICE can put out, 72hp max minus the generator and motor efficiencies. Of course they may just not have time to implement and test something like that, and may just blow the whole thing off. That would seriously impact the MPGs after discharge I would think.

Rob

[paprius4030]

Cutting to the chase. the Volt is just a local vehicle? It wouldn't be a car to go to Fl. from Pa. like we do with our Prius?

[Celtic Blue]

Rob,

That is my interpretation as well. They have indicated 30 mpg in their extended range mode. That's not very good, but if the ICE is running the whole time it is probably unavoidable with the slightly larger cross sectional area and probably 400 pounds of excess weight (plus I wonder what the efficiency will be of the path: ICE-generator-motor.) On hill climbs past ~40 miles they are going to have problems compared to the Prius (which can have its own problems.)

[Celtic Blue]

Originally Posted by paprius4030

Cutting to the chase. the Volt is just a local vehicle? It wouldn't be a car to go to Fl. from Pa. like we do with our Prius?

It's not going to be nearly as fuel efficient on long trips if the current info proves accurate. And it will suffer if you can't recharge it. (Perhaps not ideal for traveling salesmen?) I wouldn't take it on a trip to the mountains--ironically a place where sports cars are usually the most fun and the segment it has targeted to some degree.

But at least it has the capability of doing long trips. And trips on the flat shouldn't be a problem.

[usbseawolf2000]

Here is the question that needs to be asked... What if Volt climb 20 miles long mountain and runs out of battery juice at the top? Ok, it will start to operate on CS mode. Now you go back down the mountain. Will the regen brake recharge the battery pack? I would say yes. Ok, then once you reached the bottom of the hill, the pack would have recapture majority of the energy back. At this point, will the Volt operate on CS or CD mode?