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2013 Power output / regen not as much as others

10K views 102 replies 19 participants last post by  scottf200 
Oh, I drove to Tennessee and had a discharged battery in Chattanooga. As left Chatty on IH 24, I remember about the grade up to Monteagle so I engaged Mountain Mode. The engine revved up a bit and I forgot about it until I reached the beginning of the grade, I would say about 45 minutes later.

I was wide open throttle the whole way up doing only 45 mph until Reduced Engine Power came up on the drivers display and dropped to 20 or 25 mph. The battery was fully discharged again; sadly, I did not note the battery level when I started up the grade. Thankfully the Pilot truck stop was in sight where I pulled in, let the car idle in MM for about a half hour while I ate. When I returned to the car, the charge then was only at 3 bars, but it was enough for me to continue my trip.
Sounds like your Mountain Mode is not performing as expected. As I mentioned in the other thread, the youtube video Self Charging Volt shows MM recharging a fully depleted 2012 Volt’s 16 kWh battery to the MM-maintained level in 15 minutes using 0.36 gallons of gas while the car is parked. When the MM-maintained soc level is reached, since the car is not moving, the engine shuts off. I’ve experienced this with my 2012 Volt. If you are parked while recharging with MM, when the battery is recharged to the MM-level, the ICE shuts off.

The 2013 battery is slightly larger and might require a few more minutes and use a little more gas, but if you were idling at a truck stop using MM to recharge, and it took longer than ~20 minutes (did you note the amount of Gas Used?), it sounds like there’s something wrong with the MGA generator output or generator-to-battery charging system.

Note, too, that the Gen 1 Volt continues to be propelled by the electric motor in Extended Range mode. Loosely speaking, a Gen 1's gas mileage, i.e., MPGcs, is the distance you can drive on the amount of power provided to the primary traction motor by burning 1 gallon of gas in the generator. If you are generating less electricity per gallon of gas than expected, your gas mileage will suffer. 24-28 mpg is less than expected. Perhaps your generator is not performing as expected.
 
Think of your Gen 1 Volt as an electric car that can run on electricity from the battery or electricity from the generator.

When fueled by the battery in CD mode, it seems to work ok.

In CS mode, if the generator output is below programmed levels, the primary motor will need to draw power from the battery more frequently to maintain performance, and the generator will need to run for longer periods of time to maintain the battery state of charge. This would also cause Reduced Propulsion Power mode to occur sooner. Greater demand for generator output requires more gas consumption, and the "gas mileage" will suffer.

If in normal operations the engine/generator is not running continuously except under maximum demand conditions (i.e., it is being turned on and off to keep use of gas to a minimum), perhaps the system adjusted the timing of the "on/off" cycle to compensate for the gas quality on the one occasion when the tank was filled with "regular" gas. In this instance, it actually resulted in more efficient timing, which then increased the actual gas mileage.

Don’t know what type of testing could confirm that generator output is within spec and the engine/MGA clutch is fully functional. One would think that if reduced generator output was caused by internal degradation in the generator itself, the problem would also manifest itself in the opposite direction, lowering ev performance when MGA is acting as a motor while driving in two-motor ev mode.
 
Re-reading this thread stirred a thought... I wonder if the previous owner "rode the brakes." This could have led to the need to replace the brake pads... and could "riding the brakes" eventually degrade the regen/friction brake blending programming?

Another thought... when coasting at a reasonable speed, shifting from D to L should produce a noticeable increase in regen. What happens if, when coasting in D, the OP places a light pressure on the brake pedal? Putting a light pressure on the brake pedal should increase the regen (without applying any friction braking), unless some misadjustment instructs the system to decrease the regen because the (friction) brakes are being applied.
 
Actually, I may try an experiment tomorrow. My gas tank is "LOW" and it's warning me about low range, but I have not run out.

I am curious if I let it run out and get the "engine not available message" if the power levels are the same or are further reduced.
Be careful if you try this, and be sure your battery is charged.

When a Volt runs out of battery, the ICE starts up and the car continues down the road...

...but when a Volt runs out of gas, the car goes into Reduced Propulsion Mode, even if the battery is fully charged.
 
Let's say I get up to 55 mph, nice weather, climate control system off, level ground, sufficient battery in the CD mode:



If I left off in D, power usage drops to 0.5 to 1.0 kW with the bar graph showing just a little bit of yellow.

If I then press on the brakes ever so slightly, I feel a "grab" and the vehicle begins to slow. The power meter will not show any change.

If I press on the brakes firmly, I feel the same "grab" and the vehicle decelerates more quickly. I do not have a ratio for this, but I'd say somewhere about half the time the power meter will continue to show 0.5 to 1.0 kW in the yellow but I have seen it drop into the -20 kW area.



If I drop to L, the power meter now shows green and typically is showing about -15 kW but I have been watching it more and have seen it get a bit higher.

If I then press on the brakes ever so slightly, I feel a "grab" and the vehicle begins to slow. The power meter will not show any change.

If I press on the brakes firmly, I feel the same "grab" and the vehicle decelerates more quickly and the amount of regen will increase but I've not been able to make it show -50 kW or better. The -20s are easy and will frequently enough see it reach into the -30s.
My 2012 Volt has no power use meters on the driver’s display (they came along in 2013 models) so I’m not familiar with what normal displays should indicate. I’m just familiar with coasting along in D and then shifting into L and feeling the regen increase (without using the brake pedal). I wondered if you had felt a similar increase. I would think shifting from D to L increases regen by a fixed amount, and if this is how it feels to you (and I suppose your display would show the increase), it might suggest that even if the regen system is not producing sufficient correct total output, at least the proportional increase obtained when shifting from D into L is working properly...

If braking systems that blend regen and friction braking are fairly new, no one might yet know the long-term consequences of "riding the blended brake pedal." What might that constant slight pressure on the brake pedal do to a system programmed to apply regen first, friction brakes last? Perhaps over time the algorithm telling the vehicle when to apply which kind of braking and how much might need recalibration, especially if the vehicle has been subjected to prolonged periods of driving time when pressure is being applied to the accelerator and the brake at the same time.

Thus my query on the possibility the previous owner had been riding the brakes. You indicate that when lightly applying the brakes while in D or in L, the car slows faster without any change on the power meter, as if the system is choosing to engage the friction brakes at this early stage (and you have previously indicated the friction brake sound file in MyGreenVolt is being played at this early stage of brake pedal depression). Perhaps the dealer can confirm whether or not the blended braking system is correctly functioning.
 
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