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Discussion Starter #1
I gather that Volt traction battery capacity has gone from 16.0 kWh (2011-12) to 16.5 kWh (2013-14) to 17.1 kWh (2015), and finally to 18.4 kWh (Gen 2). Therefore, there should be a small range difference in the various years of Gen 1 Volts, assuming that the traction battery is always drained to the some reserve capacity that is constant. However, that may not be the case.

Does anyone know (a) how much energy (kWh) remains in the traction battery when the system shows it is empty
and switches to the ICE and (b) if this reserve energy value has been the same, year by year, in Gen 1 Volts?
 

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The 2016-17 Volt with a 18.4 KWH (total capacity) battery, when the Volt is driven in electric mode only 14-14.4 KWH are used so somewhere around 4 to 4.4 KWH are still in the battery when the Volt states there is no more electric range. Even when 0 miles for electric range is indicated the car will still pull electric from the battery in when it can replenish the electricity from the engiine to keep that 4-4 KWH reserve capacity in the battery.The Volt seems to have a mind of its own and will never let the battery drop to a certain level once the range indicator for electric displays 0 miles left.
 

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The 2016-17 Volt with a 18.4 KWH (total capacity) battery, when the Volt is driven in electric mode only 14-14.4 KWH are used so somewhere around 4 to 4.4 KWH are still in the battery when the Volt states there is no more electric range. Even when 0 miles for electric range is indicated the car will still pull electric from the battery in when it can replenish the electricity from the engiine to keep that 4-4 KWH reserve capacity in the battery.The Volt seems to have a mind of its own and will never let the battery drop to a certain level once the range indicator for electric displays 0 miles left.
Those 4 kWh are split between upper and lower safety regions and a working buffer. To avoid damage/degradation of the pack, the car never charges to 100% or discharges to 0. In addition, the engine turns on before it reaches the very bottom of the part of the battery that ghee car will allow to be used - it holds the last kilowatt hour in reserve to use like a hybrid does in making the engine more efficient. This working buffer gives you a few miles on electric after the car runs out of gas, too.
 

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Those 4 kWh are split between upper and lower safety regions and a working buffer. To avoid damage/degradation of the pack, the car never charges to 100% or discharges to 0. In addition, the engine turns on before it reaches the very bottom of the part of the battery that ghee car will allow to be used - it holds the last kilowatt hour in reserve to use like a hybrid does in making the engine more efficient. This working buffer gives you a few miles on electric after the car runs out of gas, too.
Correct, so there is somewhere between 2 and 2.4 kWh of juice left in the battery when it slows empty on the guessometer.
 

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Discussion Starter #5
OK, let's assume a battery reserve of 4.4.kilowatt-hours. I've been keeping a spreadsheet of trips in my 2015 Volt in mostly city driving, and the average miles per kilowatt-hour is 3.39. If that number is taken as a benchmark, it means that the 2011-12 Volts should have an average range of about 39.3 miles, the 2013-14 Volts should have a range of about 41.0 miles, the 2015 Volts should have a range of about 43.1 miles, and the 2016-17 Volts should have a range of about 47.5 miles. However, I should note that my average miles/kWh has a 10% standard deviation, so there's a big variation associated with these numbers.
 

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OK, let's assume a battery reserve of 4.4.kilowatt-hours. I've been keeping a spreadsheet of trips in my 2015 Volt in mostly city driving, and the average miles per kilowatt-hour is 3.39. If that number is taken as a benchmark, it means that the 2011-12 Volts should have an average range of about 39.3 miles, the 2013-14 Volts should have a range of about 41.0 miles, the 2015 Volts should have a range of about 43.1 miles, and the 2016-17 Volts should have a range of about 47.5 miles. However, I should note that my average miles/kWh has a 10% standard deviation, so there's a big variation associated with these numbers.
Keep in mind the Gen II Volt by EPA numbers is between 5% (hwy) to 12% (city) more efficient than the Gen I Volt.

Also on the Gen I Volt EV range usable battery was about: The unused battery on the Gen I Volt was 6KWh.

2011 - 2012 - 10KWh
2013 - 2014 - 10.5KWh
2015 - 11.1KWh
 

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My 2014 was rated 10.7 usable...and FYI after nearly 4 years its down to about 10.2

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Keep in mind the Gen II Volt by EPA numbers is between 5% (hwy) to 12% (city) more efficient than the Gen I Volt.
Also on the Gen I Volt EV range usable battery was about: The unused battery on the Gen I Volt was 6KWh.

2011 - 2012 - 10KWh
2013 - 2014 - 10.5KWh
2015 - 11.1KWh
 

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My 2014 was rated 10.7 usable...and FYI after nearly 4 years its down to about 10.2
How consistent is that figure? I mean, I "get" anywhere between 9.2 and 10.2 out of mine before it switches to CS mode, and that's largely seemingly dependent on ambient temperature (summer's better at extracting more kwh) and driving rate (slower driving wrings out more kwh than faster). Yesterday's was 9.6 because basically it did 38 out of 40 miles at about 60 MPH. A month ago, it got 9.9 because the 40 miles it got was city driving. Temperatures were about the same, number of miles about the same, amount on the discharge-o-meter was a half kwh different, to the same (built-in) depth of discharge.
 

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Does anyone know (a) how much energy (kWh) remains in the traction battery when the system shows it is empty and switches to the ICE and (b) if this reserve energy value has been the same, year by year, in Gen 1 Volts?
To prolong the life of the battery, the car is never allowed to fully charge or to fully discharge the battery. According to the Wikipedia article on the Chevrolet Volt, for the concept car, "the Volt team decided to use only half of the 16 kWh capacity to reduce the rate of capacity degradation, limiting the state of charge (SOC) up to 80% of capacity and never depleting the battery below 30%... According to GM, as of August 2016, no batteries have been changed due to degradation..."

That SOC window was expanded to 65% for the Gen 1 Volt, and appears to have been expanded to ~77% for the Gen 2.

2011/2012: 16.0 kWh x 65% = 10.4 kWh usable
2013/2014: 16.5 kWh x 66% = 10.9 kWh usable
2015: 17.1 kWh x 65-66% = 11.1-11.3 kWh usable
This ~0.7 kWh increase in usable power from 2011 to 2015 provided a noticeable, but not dramatic increase in range.

2016/2017 18.4 kWh x 77% = 14.2 kWh usable

Although the exact settings for the max/min numbers are proprietary, from OBD readings on my 2012 Volt, the Gen 1 appears to use a 65% SOC window of ~20%-85% or ~22%-87%. I’ve seen no numbers on the Gen 2 window. I think I’ve read of 15% as a hard floor setting for the window. The amount of energy remaining in a fully depleted battery is thus likely to be a consistent % of the battery capacity, which means the actual amount varies with the battery capacity.

Note that the 53 ev mile rated range of the Gen 2's 14.1 kWh usable battery = 3.76 mi/kWh, whereas the 35 ev mile rated range of the 2011/2012's 10.4 kWh usable battery = 3.37 mi/kWh, an improvement in efficiency. As many of us know, actual numbers cycle as the season warm up and cool down.

In practice, the size of the SOC window can depend on operating conditions. The Volt’s Battery State Estimate Algorithm calculates SOC readings "on the fly," and when it estimates the "minimum SOC point" has been reached, will transition the car from Electric Mode to Extended Range Mode. If before that point is reached, the car is stopped for a sufficient time, additional data is gathered and the SOC estimate may be revised. If this adjustment revises the SOC upward, additional energy can be used before reaching the minimum. If you don’t stop or the computer doesn’t revise that reading, you switch to ICE sooner. Exactly when you switch to ICE can vary depending on a number of factors. The faster you drive, for example, the less lead time the computer has to estimate accurately when the minimum SOC number has been reached. Many factors may affect the kWh Used number for a full depletion.

It’s also said that frequent short trips followed by immediately plugging in to recharge can, over time, corrupt the Battery State Estimate Algorithm, causing the computer to overestimate power consumption rates, shrinking the usable SOC window (reducing your kWh Used numbers for a full depletion). One method of recalibrating the algorithm is by doing a number of full charge/full depletion cycles, instead of immediately recharging a partially depleted battery.
 

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Normal engine on is 19% (22% for 16 kWh batteries with older charge points) - I don't think this has changed for new volts. They just raised the max charge level to get the extra 10%.
WOT said Emergency floor is 15%, but never confirmed if that was the same for all models or also adjusted with the '13 charge point shift. Emergency meaning your engine has died and it switches back to battery for a short while so you can get to a safe place.

Assuming the same bottom level, 4-7% of total capacity in reserve.
16 kWh: 1.1kWh
16.5 kWh: 0.66 kWh
17.1 kWh: 0.68 kWh
18.4 kWh: 0.74 kWh
 
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