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With the $12 gadget below, and an app called torque, you can see the engine's RPM. So I turned on mountain mode and left it in the parking lot. 20 minutes later the car went from empty to 1/2 charged (after a 50% charge mountain mode stops so I couldn't get more than 50%).

What's amazing is mountain mode only requires 1,600 RPM!!!! How could so little engine use charge 50% of the battery in 20 minutes?!!?!

https://www.amazon.com/dp/B0156E5JA0?tag=vs-auto-convert-amazon-20
 

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You could ask the same question about an ICE running at 1600 RPM in 5th gear and moving a car at 70MPH.


Engine RPM doesn't have much to do with power output. You can have high load and power output at a low RPM.
 

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You could ask the same question about an ICE running at 1600 RPM in 5th gear and moving a car at 70MPH.


Engine RPM doesn't have much to do with power output. You can have high load and power output at a low RPM.
You're saying an engine with low RPM can put out a lot of horsepower? Seems counterintuitive but I guess it can be true.

Maybe RPM = torque, not horsepower?
 

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If you do the math, it's not very shocking. MM doesn't do 50%, it's more like 3.5 kWh or so (someone will correct me, I'm sure). A 15kW (almost 1C charge rate for gen1) for 15 minutes yields 15kw x .25 hr = 3.75 kWh... which is ballpark for what happens. That 15kW is 20hp, I'm sure the ICE can manage 20hp at 1600 RPM. It seems super fast because our normal max charge rate is 3.3kW.
 

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10.8kWh * (50%/100%) = 5.4kWh.
5.4kWh / (1hr/.333) = 16.2 kW
Converted to HP/TQ: 22 HP & 72ftlb @ 1600 rpm.
 

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When coasting and the engine is "recovering charge" in my Gen 2 (after heavy acceleration), the battery power gauge goes down into the green almost as far as during regenerative braking. That means the engine can put something like 40-50 kW into the battery when it's revved up, so it probably puts at least 15-20 kW in at 1500 RPM. A 16A 240V charger would put out about 3.8 kW, and that will charge a Gen 2 (14.5 usable kWh) in about 4 hours. At 20 kW, a Gen 2 could be fully charged in under an hour.

A neat experiment would be to see if any model years load up the engine when the hood is open and the vehicle's on, or if it just idles under no load. If it's loaded and charging the battery, that might be a (somewhat counterintuitive) way of fully charging the battery when unable to charge. The only use for that I can see is being able to show off EV driving when not near a charging station and no charge left.
 

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A neat experiment would be to see if any model years load up the engine when the hood is open and the vehicle's on, or if it just idles under no load. If it's loaded and charging the battery, that might be a (somewhat counterintuitive) way of fully charging the battery when unable to charge. The only use for that I can see is being able to show off EV driving when not near a charging station and no charge left.


Opening the hood with the car "on" does start the engine and charge the battery. Some people tried to hook up a switch to use this as a Hold mode before the Gen1 got true Hold, but found that the car throws an error code after you do it a few times.


Using mountain mode to charge the battery is inefficient. Remember that the purpose of mountain mode it to charge the battery to help when climbing a steep grade. So, when you put the car in MM it thinks that you're about to climb a mountain and needs to build the battery charge ASAP. It does that without regard to efficiency.
 

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Opening the hood with the car "on" does start the engine and charge the battery. Some people tried to hook up a switch to use this as a Hold mode before the Gen1 got true Hold, but found that the car throws an error code after you do it a few times.


Using mountain mode to charge the battery is inefficient. Remember that the purpose of mountain mode it to charge the battery to help when climbing a steep grade. So, when you put the car in MM it thinks that you're about to climb a mountain and needs to build the battery charge ASAP. It does that without regard to efficiency.
Right; it just runs at a constant RPM and (obviously) doesn't do much in the way of mechanical assistance using the engine (although Gen 2 will still use the engine mechanically in Mountain Mode at very specific speeds).

With respect to the hood trick pre-hold-mode, I'd imagine the car gets pretty upset if the hood is opening and closing while moving, and if it detects the hood closes while moving, it probably throws the code because it thinks the hood sensor is bad.
 

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With the $12 gadget below, and an app called torque, you can see the engine's RPM. So I turned on mountain mode and left it in the parking lot. 20 minutes later the car went from empty to 1/2 charged (after a 50% charge mountain mode stops so I couldn't get more than 50%).

What's amazing is mountain mode only requires 1,600 RPM!!!! How could so little engine use charge 50% of the battery in 20 minutes?!!?!
So now if another EV owner says that your Volt can't do DC Fast Charge, you can tell them that, in fact, it does and it does it without even being plugged in. :eek:
 

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So now if another EV owner says that your Volt can't do DC Fast Charge, you can tell them that, in fact, it does and it does it without even being plugged in. :eek:
Ah, but see, that's "AC Fast Charge"! But...maybe that's better? ;)
 

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Ah, but see, that's "AC Fast Charge"! But...maybe that's better? ;)
Doesn't it get converted to DC before it goes into the battery? Just like the public DCFC stations.
 

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With the $12 gadget below, and an app called torque, you can see the engine's RPM. So I turned on mountain mode and left it in the parking lot. 20 minutes later the car went from empty to 1/2 charged (after a 50% charge mountain mode stops so I couldn't get more than 50%).

What's amazing is mountain mode only requires 1,600 RPM!!!! How could so little engine use charge 50% of the battery in 20 minutes?!!?!

https://www.amazon.com/dp/B0156E5JA0?tag=vs-auto-convert-amazon-20
First, because it doesn't go to 50%. Second, because it's a fairly small battery. Third, because the car pretty much always runs at wide open throttle, whereas you've likely never come across another car doing WOT at 1600 rpm.

As flyingsherpa said, the actual additional charge in mountain mode is about 3.5 kWh - just over a third of the usable window (for the early cars - not sure if it increased proportionally for the slightly larger battery pack of later cars or not.)

Here are the bsfc maps for the 1.4l, from a very old post:

http://gm-volt.com/forum/showthread.php?3739-VOLT-MPG-estimate-using-BSFC-maps&p=105221#post105221

At 1600 rpm and 100 Nm, the car is generating ~16.8 kW:

http://www.wentec.com/unipower/calculators/power_torque.asp

So it's certainly not hard to believe that you can get 3.5 kWh from 17 kW in 20 minutes (perfect efficiency would give you 5.7 kWh...)
 

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Doesn't it get converted to DC before it goes into the battery? Just like the public DCFC stations.
Well, yes, that's always the case I suppose. It was mainly a joke because the engine produces AC. The "DC" indication on DCFC is because the power running through the EVSE cable is DC on DCFC, as opposed to AC for Level 1 and 2, meaning the onboard charger wouldn't have to convert it...I believe that's why DCFC can transfer much higher currents.

just over a third of the usable window (for the early cars - not sure if it increased proportionally for the slightly larger battery pack of later cars or not.)
Gen 2s only charge to 2 notches on the battery meter (20%). This is roughly 10 miles for me, which is something like 2.5 or 3 kWh. The Gen 2 doesn't really need mountain mode to begin with, so there was no point increasing the charge window for it.
 

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If you push the pedal down in park it will bump up to ~16kW and 2000rpm.
Standard is ~11kW IIRC.
 

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You're saying an engine with low RPM can put out a lot of horsepower? Seems counterintuitive but I guess it can be true.

Maybe RPM = torque, not horsepower?
You're saying an engine with low RPM can put out a lot of horsepower? Seems counterintuitive but I guess it can be true.

Maybe RPM = torque, not horsepower?
to be precise, power equals torque x RPM, so increasing either torque or RPM or both will increase power output. Generally (and somewhat oversimplified), an ICE will be most efficient at wide open throttle and at the lowest RPM it can tolerably run at. If that torque x RPM product is not sufficient power, then RPM must be increased e.g. by shifting to a lower gear in a conventional car, or adjusting the generator output current in the volt (reducing the output current will lower torque required and result in a higher RPM for the same WOT setting; power out will increase since output voltage will increase at the higher RPM- similar to shifting to a lower gear)
 

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Arcanox said above: "The Gen 2 doesn't really need mountain mode to begin with ... "

Never heard that before. Why not? What is the source of this statement?
 
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