larryh

End of life is defined when the HVB capacity drops to 80% of its initial capacity. The results I have posted above do not include degradation due to cycling. But from post 8, the degradation due solely to cycling will be about 1.5% after 10 years. Degradation due to cycling is much smaller than calendar fade degradation. In that post, degradation due to calendar fade is 14 times larger than degradation due to cycling. Since cycling degradation has such a small impact on overall degradation, I ignore it. The errors in my estimates for calendar fade are going to be much larger than degradation due to cycling. The SOC of the HVB as reported by the BECM changes between the time I park at work (5:40 am) and the time I leave (4:10 pm). The BECM estimate of SOC is not 100% accurate and the battery cools down. It typically falls from 74% to 68%. At night the opposite happens, it rises from 43% at 4:20 pm to 45% at 3:00 am (even though the battery cools). Yes, it would be better to start charging later in the morning. But unfortunately, I do not always end up with 45% SOC from the previous day. Sometimes it as low as 15% depending on what I did the previous day. I will have to see if I can figure out how to adjust charging that is not too difficult to manage. If I started charging at 4:00 am, the model predicts a lifetime of 12.6 years instead of 11.3 years.

Suppose I extrapolate the results plotted above to determine the overall degradation rate for the calendar year. The following shows the average high temperature in Minnesota for each month and the corresponding degradation rate that I estimate for that month based on the commute to work described in post 12. Month Avg High (F)Capacity Fade Rate (1/sqrt(day))x1E-3 Jan 24 1.26 Feb 29 1.38 Mar 41 1.69 Apr 58 2.23 May 69 2.64 Jun 79 3.06 Jul 84 3.29 Aug 81 3.15 Sep 72 2.76 Oct 58 2.23 Nov 41 1.69 Dec 27 1.33 The average capacity fade rate for the year is computed as the average of the values for each month. (Actually you have to take the square root of the average of the squares.) I come up with an overall capacity fade rate of 2.34E-3/sqrt(day). The following chart shows the predicted degradation of the HVB with time based on an average fade rate of 2.34E-3. The actual degradation after 3 years is approximately 5%. The predicted degradation from the chart is about 7%. The prediction is going to be off due to many simplifying assumptions. For one thing, I don't drive the car to work 7 days a week. It usually gets a rest over the weekend. Note that if the fade rate is a, then the predicted HVB degradation after d days is degradation = a * sqrt(d). After 15 years, degradation will be approximately 17%. The HVB should last the life of the car.

This chart shows the capacity fade rate for the HVB during a typical summer weekday when I drive to work. Rather than showing the actual fade rate, instead the graph shows the battery lifetime at that fade rate. The higher the fade rate, the shorter the battery lifetime. I charge the HVB starting at 3:00 am. The HVB SOC is 45% and the temperature is 84 F. The capacity fade rate is at its minimum for the day (battery lifetime is at its maximum). If the HVB SOC and temperature were fixed at these values, the battery would last about 20 years--the chart shows the battery lifetime is 20 years at 3:00 am. Charging completes at 4:30 am. The SOC is now 98% and temperature is 88 F. The capacity fade rate is now at its maximum for the day (lifetime is at is minimum). If the HVB SOC and temperature were fixed at these values, the battery would now last less than 5 years--the chart shows the battery lifetime is less than 5 years at 4:30 am. I want to use up the SOC quickly to prevent rapid degradation to the HVB. Do not leave the battery at a high SOC for very long. I start for work around 5:20 am and arrive around 5:40 am. You can see the battery lifetime going up during this period as the battery is discharged. At the end of the commute, the battery SOC is 68% and temperature is 93 F. I leave work around 4:00 pm. During the day the battery cools to 88 F and the battery lifetime rises slightly from just below 10 years to just above 10 years. I arrive home at around 4:20 pm. The battery SOC is now 45% and temperature is 93 F. During the night, the battery cools and the lifetime increases from 15 years at 4:20 pm to 20 years at 3:00 am. If I compute the average lifetime over the entire day, I get 11.3 years. If I drove the car under these conditions every day for the next several years, the battery would last for 11.3 years. The average high temperature for the week was 80 F. Had the high been 90 F, lifetime would have been reduced to 8.5 years. Had the high been 110 F, lifetime would have been reduced to 4.4 years. At 60 F, lifetime is 20.7 years. If instead of charging the HVB to 100% SOC, I charged to 70% SOC, the lifetime would increase from 11.3 to 20.7 years. Unfortunately, there is no easy way to stop charging at a given SOC.

This chart explains why you want to delay charging until the last possible moment and to charge as fast as possible. This chart assumes a typical summer day in Minnesota. I arrive home from work at 5:00 pm and leave for work at 5:00 am. When I arrive home, the HVB temperature is 91 F. The garage temperature during the night is around 70 F. The battery cools at a rate of about 1.3 F degrees per hour when not being charged. If I charge with a Level 2 charger, the HVB temperature increases at a rate of about 3.6 F degrees per hour. If I charge at a slower rate, the temperature rises proportionately slower. The chart shows five choices for charging: 1. Charge at plug-in as fast as possible using a Level 2 charger (takes 2 hours to charge). [Plug-in 2 hour charge time] 2. Charge at plug-in at a rate such that charging completes in 6 hours (Level 1 charger). [Plug-in 6 hour charge time] 3. Charge slowly at plug-in all night long so charging takes 12 hours and completes at 5:00 am. [12 hour charge time] 4. Wait 6 hours to begin charging and then charge at a rate such that charging completes in 6 hours at 5:00 am (Level 1 charger). [Delayed 6 hour charge time] 5. Wait 10 hours to begin charging and charge using a Level 2 charger (takes 2 hours to charge) so that charging completes at 5:00 am. [Delayed 2 hour charge time] The chart plots the the capacity fade rate for each option at each time throughout the night. Time 0 corresponds to 5:00 pm when the charger is plugged-in. Time 12 corresponds to 5:00 am when I leave for work. Consider the curve for option 1 for which charging completes in 2 hours after plug-in. The SOC of the battery at plug-in is 20% and the temperature is 91 F. This corresponds to a fade rate of 2.2e-3 as indicated by the light blue line at time 0. The battery now charges and the capacity fade rate increases. At time 2 hours, the HVB is at 100% SOC and the temperature is 98.6 F. The fade rate is 6.2e-3 as indicated by the light blue line at time 2. The battery now cools at a rate of 1.3 F degrees per hours and the fade rate decreases to 5.2e-3 at 5:00 am. Option 1 degrades the battery the most, followed by option 2, 3, 4, and finally, option 5 degrades the battery the least. You can see that the capacity fade rate for option 1 equals or exceeds that for all the other options at any time. Similarly, the capacity fade rate for option 4 equals or exceeds that for options 3, 2, and 1 at any time. I can compute an upper bound on the battery lifetime for each option by computing the average fade rate for each of the curves (area under curve divided by time). The result provides an upper bound on the battery life since I am missing what happens to the battery for the remaining 12 hours of a day that it is not in the garage. Whatever happens then will only degrade the battery further. 1. 7.6 years 2. 10.4 years 3. 20.2 years 4. 30.7 years 5. 44.5 years If you plug in and start charging the car immediately after arriving home using a Level 2 charger, the battery will last less than 7.6 years. If you wait until 3:00 am to charge using a Level 1 charger, the upper bound on battery lifetime is 44.5 years--it will be less because I have not taken into account degradation of the battery occurring during the day from 5:00 am to 5:00 pm. If you live in a warmer state, the upper bounds will be significantly less. For Phoenix, the upper bound on battery lifetime for option 1 is about 3.5 years.

Note that most of the heat generated while charging comes from three chargers inside the car used to charge the HVB. Their temperatures get well over 150 F. It is not the HVB by itself that is generating all the heat. If it is 100 F outside, the HVB temperature is probably around 110 F. At those temperatures, the HVB will start to degrade rapidly when the SOC of the battery as reported by MFT/MFM exceeds 40%. It is alright to charge the battery, but use the charge up right away so that the average SOC of the battery over a day is less than 40%. Delay charging (using Value Charge) until early in the morning so it finishes just before your commute to work. Since the car does not do a good job of managing the HVB temperature and SOC, the owner is going to have to do it. If you don't take steps to mitigate HVB degradation, the battery capacity could be reduced to less than 80% in two to three years as other have experienced. In addition to delaying charging so it completes right before you leave and avoiding sustained high battery charge, there are some additional steps you can take. Park the car in cool locations out of direct sunlight. Moderate driving. Use EV later mode when driving on the freeway. If it is really hot (>115 F), consider not charging the car at all and drive in hybrid mode. If you don't need a full charge for your trip, then only put in enough charge to complete your trip.

See this post regarding how the venting for the HVB works: http://www.fordfusionenergiforum.com/topic/1683-obd-ii-data-for-hvb/?p=21758. While charging, the car draws in outside air from a vent located under the long black tube in the picture. The inlet is under the car near the bumper. The hot air is vented into the passenger compartment behind the rear passenger seat as you stated. The vents in the rear deck of the car are used when the car is running and the passenger compartment is cooler than outside. Air cooling is not all that effective in cooling the HVB. Liquid cooling would do a much better job. The HVB is going to be approximately 10 F degrees higher that the outside temperature. The best way to deal with high temperatures is to keep the State of Charge of the HVB low. Delay charging the car until you are ready to go. Don't keep the battery at a high SOC any longer than necessary. It is the combination of high SOC and high temperatures that cause rapid battery degradation.

The following chart is the same as the bottom chart in the first post, except now the contour lines are HVB temperature. This chart emphasizes the importance of maintaining a low average SOC for the HVB. You should never leave the HVB fully charged for an extended period of time. If the HVB temperature is 100 F, then follow the blue 100 F contour line. At 100% SOC, the battery will last 2.8 years. If instead, you keep the HVB temperature at 100 F and SOC at 20%, the battery will last 18 years. If the HVB temperature is 50 F, then it will last more than 10 years no matter what SOC is maintained. You want the battery to last the life of the car, which generally considered around 10 years. When outside temperatures are hot, you especially want to be sure that you delay charging the battery until the last moment, that you charge the car quickly, and that you drive off immediately after charging completes and start using up the charge in the battery. The less time the battery spends at a high SOC, the better. When it is extremely hot, you might want to consider driving the car in hybrid mode and not charging the battery.

Notice from the charts in the previous post, compared to Calendar (storage) degradation, Cycling degradation (charging/discharging) seems to be less dependent on HVB temperature. It is clear from the left two charts, that the warmer the battery, the greater the Calendar degradation (all the Phoenix trips result in greater degradation than all the Minneapolis trips). The increase in degradation with temperature is exponential. Temperature impact on resistance growth is especially evident (bottom left chart), implying high battery temperatures degrade the maximum power output of the battery much faster than lower temperatures. The same is true for battery capacity (top left chart), but the impact of high temperatures, while significant, is not quite as great. From the right two charts, it appears that the main affect of higher temperatures with respect to Cycling degradation is to increase the variability of both capacity loss and resistance growth. Rather than shifting the boxes upward as on the left side, the height of the boxes are expanded. For moderate trips and driving, there is a small increase in the rate of degradation with increasing temperatures. For an average battery temperature of 285 K, the average degradation due to resistance growth is about 6%. For an average battery temperature of 300 K, the average degradation due to resistance growth is about 8%. However, at higher temperatures, more aggressive trips and driving results in disproportionately more degradation with temperature. The maximum degradation due to resistance growth is 12% when battery temperature is 285 K. The maximum degradation due to resistance growth is 17% when the battery temperature is 300K. In effect, higher temperatures are magnifying poor driving/charging behavior. So driving/charging the car with a hot battery does increase degradation a small amount. The degradation increase is minimal for short trips/shallow charging. It becomes more significant with longer trips/longer charging. But the main reason for the increase is degradation of the HVB at high temperatures is due to the the fact that the battery is simply hot (and at a high SOC) and not because you are driving/charging it when it is hot.

The following chart shows the relative importance of Calendar and Cycling degradation effects for three different locations for an EV: Minneapolis, Los Angeles, and Phoenix. This is from a presentation that can be found at http://www.nrel.gov/docs/fy13osti/58550.pdf. The top two charts are Calendar and Cycling capacity degradation after 10 years. The bottom two charts are Calendar and Cycling resistance growth after 10 years, i.e power degradation. Each marker represents one of 317 different trip histories (DOD). The different colors of the markers indicate a low, median, and highly aggressive driver (charge/discharge rate). To compute total capacity degradation due to Calendar and Cycling losses, you need to add the degradation for a trip on the top left chart to the degradation for the corresponding trip on the top right chart. In Minneapolis, the minimum overall 10 year capacity degradation is 21% and the maximum is 30%. In Phoenix, the minimum is 29% and the maximum is 45%. Climate has the greatest effect on battery degradation. Drivers in Phoenix will experience greater battery degradation no matter what they do as opposed to drivers in Minneapolis or Los Angeles who treat their batteries poorly. Trip history has the next greatest affect. And finally, driver aggression. With respect to capacity degradation, Calendar losses have a far greater impact than Cycling losses. In Minneapolis, Calendar losses will be about 22% after 10 years. Cycling losses will be about 1.5%. So Calendar losses are 14 times greater. Similar results apply to the other locations. If you want to preserve the capacity of the HVB, your main priority should be keeping a low average temperature and/or a low average SOC. With respect to power degradation, Calendar losses still have a greater impact than Cycling losses. But now Calendar losses are only twice Cycling losses. To reduce power degradation loss, you now need to be concerned with cycling losses due to DOD, temperature, and initial SOC of the HVB. Driver aggression, i.e. charge/discharge rates, has only a minor impact on degradation over the 10 year period, i.e. about 2% for capacity and 4% for power loss. I'm not sure how directly these results apply to the Energi. So according to this paper, the factors that determine degradation of the battery in priority order are climate, commute, and driver aggression.

In addition to the Calendar (storage) degradation discussed above, further degradation occurs due to cycling of the battery. The total degradation of the battery is the sum of these two effects. Each time you charge/discharge the battery, you are adding additional degradation to the battery above and beyond the calendar effects discussed above. You can find the results of cycling the Chevrolet Volt's battery for 4323 cycles in the paper "Investigation of battery end-of-life conditions for plug-in hybrid electric vehicles" by Eric Wood, Marcus Alexander, and Thomas Bradley. Just search the internet. In that paper, each cycle consisted of driving the car in EV mode until the battery was depleted to a specified SOC (EV range for the Volt is 38 miles). Then the car was driven in hybrid mode for a total trip distance of 50 miles. They did not actually drive a car. Instead, they applied a simulated load to the battery for a driver who drives aggressively. The battery was allowed to rest for 15 min and then was charged. After charging completed, the battery was allowed to rest for one hour and then the next cycle began. Each cycle took 7.3 hours. They did 4323 cycles or approximately 10 years worth of driving if the car is cycled approximately once per day. They tested three batteries. For the first battery, the battery was only discharged from 80% to 20% SOC, i.e. 60% DOD (depth of discharge)--which is close to what the Volt actually does. The second was cycled with 70% DOD, and the last battery was cycled with 80% DOD. The battery capacity degradation never exeeded 20% for any of the batteries. Degradation was linear, i.e. a constant amount of degradation occurred with each cycle. Power degradation was about 15% for 60% and 70% DOD after 4323 cycles. Degradation was linear However, the power degradation did exceed 20% for 80% DOD at 3650 cycles. It was linear to about 2400 cycles with 80% DOD and then degradation began accelerating. Cycle degradation increases with increasing DOD. You want to keep DOD to less than 70%. DOD greater than 70% will shorten the life of the battery. The DOD for a fully depleted Energi battery is 100% - 15% = 85%. That is way too aggressive. If you constantly deplete the HVB every day, the battery will reach end of life before 2400 cycles, or before 6.6 years due to cycling alone. If you do it twice a day, then it will reach end of life before 3.3 years due to cycling alone. As a consequence of power degradation due to cycling, acceleration times will be reduced. Normally, the Volt accelerates to 60 mph in a little over 9 seconds. For the battery with 80% DOD after 4323 cycles, the acceleration time was still just over 9 seconds when the battery was fully charged. However, as the battery is depleted, acceleration becomes sluggish. When the battery SOC reaches 30%, acceleration times increase to 15 seconds. Note that for my round-trip commute, I discharge the battery from approximately 100% to 40%, or 60% DOD. So cycling degradation isn't going to be a concern for me. However, anyone who has a long commute and charges the HVB immediately after arriving at work and at home is going to experience rapid degradation due to Calendar effects from high HVB temperature and SOC and from Cycling effects due to high DOD.

Consider the Chevrolet Volt. It has an active liquid cooling system that attempts to maintain the battery temperature around 25 C. Provided the car is either running or plugged in, the battery temperature should be around 25 C. In addition, the battery is never charged above 80% SOC. Looking at the charts above for 80% SOC and 25 C, that operating point is within the desired region, i.e. below the X=10 year line in the top chart, and above the X=10 year line in the bottom chart. Disregarding cycling of the battery, the battery should last for at least 10 years before 20% degradation. However, the car is likely to remain off and not plugged in for long periods of time, so degradation may be a worse than predicted. You can see the actual degradation for a Volt operated in Phoenix (under similar conditions to the Energi) for three years and 120,000 miles here: https://avt.inl.gov/vehicle-button/2013-chevrolet-volt. Capacity degradation was about 9%. But again, the car was operating in hybrid mode for most of the time. For the Volt, the excessive degradation observed by some for the Fusion Energi after only 3 years should not occur. Unlike the Volt, the Energi is charging the battery to 100% SOC (it actually charges to about 95% SOC, but that is not much of an improvement) and does not actively manage the HVB temperature when the car is off or plugged in. I suspect this is the main reason people are observing high degradation rates. The average temperature and SOC of their HVB is too high.

I would try to keep the HVB in a state that is above the X=10 years line on the bottom chart and below the X=10 years in the top chart. The HVB temperature should be somewhere between the high and low daily temperature if the car is parked for a week. Assume a mean temperature of 85 F or about 30 C for the days the car was parked and that the HVB temperature was around that temperature. At 60% SOC and 30 C, you are well within the desired regions of the chart. If you were in Phoenix, you would not be. However, note that if MFT/MFM is reporting 60% SOC, the actual SOC of the battery is 20% + 80%*0.6 = 68%. If this is the case, you are just barely within the desired regions. MFT/MFM reports the HVB SOC as 0% when the actual SOC is 20%. MFT/MFM reports HVB SOC as 100% when actual SOC is 100%. So you have to adjust the MFT/MFM SOC to get the actual SOC to use in the charts above. Also note, that if you drove the car during the day, the HVB temperature would be about 10 F above the outside temperature. So if it is 100 F, the HVB might be 110 F or about 45 C. In that case, you would want the SOC to be 30% or less when you park. MFT/MFM would report 12%. But if not, the HVB will eventually fall and degradation will again be inside the desired limits.

Now consider someone in Phoenix, AZ. During the summer, the HVB temperature will be around 45 C and during the winter around 27 C. At 100% SOC, that corresponds to capacity fades rates of -7.4e-3 and -4.8e-3 (the value for 45 C is off the chart so I have to guess). Assuming 50% of the time is winter and 50% is summer, the average degradation rate is the average of those two numbers or -6.1e-3/sqrt(day). At that rate, the battery capacity degradation will reach 20% in 2.9 years. The actual degradation will be greater than 20% after 2.9 years since I have not included degradation due to cycling. A test of the Nissan LEAF driven in Phoenix, AZ can be found here: https://avt.inl.gov/sites/default/files/pdf/vehiclebatteries/FastChargeEffects.pdf. In this test, the actual battery degradation was 25% after 1.5 years. Cycling was probably responsible for 8% of the 25% degradation. Now suppose that the person in Phoenix does not charge the car and drives it as a hybrid so the HVB SOC is approximately 20% all year round. The average summer/winter capacity fade rate will then be approximately -2.4e-3/sqrt(day). Battery degradation will reach 20% after approximately 19 years, i.e. the battery lifetime is 8 times longer at 20% vs 100% SOC!. Again, I have not included cycling effects. An actual test of a Fusion Energi driven in Phoenix, AZ can be found here: https://avt.inl.gov/vehicle-button/2013-ford-fusion-energi. They charged the cars once per day in the evening so the HVB was at 100% SOC during the night (and probably all day Sunday). The cars were driven as part of a courier fleet for legal documents. After the HVB was depleted, they continued driving the car in hybrid mode the rest of the day. As a result, the SOC of the HVB would have been below 20% most of the day. After 100,000 miles and 1.5 years, actual battery degradation was 8%. If I assume the car is at 100% SOC for half the day and 20% for the other half, I come up with an average fade rate of 4.5e-3/sqrt(day). According to the model, degradation will reach 20% after 5.4 years. The model predicts 10% degradation after 1.5 years corresponding to a fade rate of 4.5e-3/sqrt(day)

As an example of how we can use the chart to determine HVB degradation, consider my typical commute to work. I charge the HVB right before I leave for work. I park at work for about 9 hours. Then I leave the battery uncharged until the next day. While at work, the SOC of the battery is around 70%. At night, it is around 40%. The HVB temperature is generally around 10 F warmer than the outside temperature. So let us assume a typical summer day in Minnesota at 85 F. The HVB temperature will be around 95 F. So as an approximation, I have the HVB at 95 F and 70% SOC for 9 hours and at 95 F and 40% SOC for the remaining 15 hours. Using the chart, the average capacity fade rate will be: 9/24*(-3.6e-3)+15/24*(-2.6e-3)= -2.98e-3/sqrt(day). That corresponds to 12 years until 20% capacity degradation. Since, it is not summer all year, and temperatures are much colder in the winter, degradation should be less than 20% after 13 years. Note that this only accounts for degradation when the battery is not cycling, i.e. not charging/discharging. I would have to compute the degradation due to cycling and add that to the 20% degradation. The actual degradation of my HVB has been 5% in 3 years. Using a degradation rate of -2.98e-3/sqrt(day), the model predicts degradation is 10% after three years. The prediction is off because I need to lower the capacity fade rate to account for winter. Now suppose that I charged the battery immediately when I arrived at work and when I returned home, so basically the SOC of the battery is 100% the entire day. The fade rate from the chart for 95 F and 100% SOC is -5.9e-3/sqrt(day). At that rate, I would reach 20% degradation in 3 years!!! Quite a difference from 12 years. (Of course, the battery temperature wouldn't be 95 F in the middle of January so the actual degradation would be less in Minnesota--but it may be 95 F in some portions of the country in January.) Don't leave your battery fully charged for any longer than necessary. Delay charging until the last possible moment.

The following chart shows the degradation rates for an NCA Lithium-ion battery stored at a constant SOC and temperature (http://www.nrel.gov/transportation/energystorage/pdfs/53817.pdf). A description of the different types of Lithium-ion batteries can be found at the following link: http://www.batteryuniversity.com/learn/article/types_of_lithium_ion. This is the type of battery used in the Tesla Model S (http://batteryuniversity.com/learn/article/bu_808b_what_causes_li_ion_to_die). The type used in the Energi, Volt, and LEAF is NMC/Lithium Manganese Oxide (http://articles.sae.org/11705/). I suspect that the Energi HVB has higher degradation rates than NCA, but the degradation rates should be comparable. The top chart shows resistance growth which correlates with power loss. A 20% increase in resistance results in a 17% power output loss from the HVB. The bottom chart shows capacity fade rate which correlates with capacity loss. As an example how to read the bottom chart, consider a battery stored at 25 C and 100% SOC. The capacity fade rate from the chart is -4.7e-3/sqrt(day). To determine the time to 20% capacity loss, we compute (0.2/4.7e-3)^2 = 1810 days = 5 years. If you wish to compute the capacity degradation for a battery stored for one year (365 days) at 100% SOC and 30 C, look at the 100% SOC line in the bottom graph where it intersects a vertical line drawn through 30 C on the x-axis. This occurs at -5.2e-3/sqrt(day) fade rate on the y-axis. The degradation is then sqrt(365)*5.2e-3 = 10%. The dashed horizontal lines indicate the lifetimes for 20% capacity loss or resistance growth. For example, consider capacity loss. The 10 year line crosses the 80% SOC line at about 27 C in the bottom chart. That means the battery capacity loss will be 20% after 10 years if the battery is stored at 80% SOC and 27 C. The point on the 80% SOC line corresponding to 20 C is above the 10 year capacity loss line. That means that degradation of the battery will less than 20% after 10 years if stored at 80% SOC and 20 C. Based on the charts below, if you store the battery at 50% SOC for 10 years, the power loss and capacity loss should be less than 20% for HVB temperatures up to 35 C, or 95 F. The normal recommended SOC for storing Lithium-ion batteries is between 30% and 40%. If you store the battery at 30% SOC for ten years, degradation should be less than 20% for HVB temperatures up to 45 C, or 113 F. To minimize degradation, ideally you would want to store the battery at 0% SOC. But that is not recommended, especially for batteries that are connected to devices. Should the cell voltage fall below 3.0 V, the battery will be irreparably damaged. That can happen if the car draws too much power from the HVB when the SOC falls below 0%. So I would not want to drain the HVB to 0% SOC. Note that when MFT/MFM reports 0% SOC of the HVB, the actual SOC is about 20%. So you need to take that into account when using the SOC reported by MFT/MFM.

I have two ruined outlets from using the Level 1 Charger--recently installed. I am using a third one that seems to be working fine for the past couple of years.

That web site also tested four Nissan LEAFs under about the worst scenario possible. The actual degradation that one will experience is highly dependent on your location, commutes, and charging practices. They drove the cars 50,000 miles over the course of about 1.5 years. 1. The location was Phoenix, AZ. In the summer, the average temperature of the HVB was 110 F. Battery temperatures got up to 130 F on occasion. The battery in my car is very rarely over 110 F in MInnesota. 2. They fully charged and almost fully discharged the battery twice daily for the morning and evening commutes. The greater the depth of charge, the faster the battery will degrade with each cycle. Ideally, one would charge the battery to approximately 80% SOC and discharge it to about 30% SOC to reduce degradation. 3. They plugged the charger in immediately after they arrived at their destinations. They should let the battery cool down first. Also, they should delay charging to the last possible moment before departing for their trips. If they plug in immediately, the battery will be at a high SOC for much of day which results in faster degradation. 4. For two of the cars, they used DC Fast Charging (approximately 2C rate). If you charge the battery faster than approximately 0.8 C, you will experience greater battery degradation. For the two cars that were charged with a Level 2 Charger, the degradation was 75% over 1.5 years. For the two cars using DC Fast Charging, the degradation was 73%. When you get to that level of degradation, power output (acceleration performance) will be severely impacted when the SOC falls below about 30%.

This web site contains information on the actual degradation of the batteries of cars placed in service in a courier delivery service for legal documents in Phoenix, AZ: https://avt.inl.gov/vehicle-type/all-powertrain-architecture. For the most part, the cars were charged once in the evening after deliveries were completed. During the day, they ran in EV mode until the battery was depleted and then for the remainder of their trips they ran in hybrid mode. This represents a difficult scenario for batteries, i.e. very warm temperatures and full cycling of the batteries. However, the batteries did spend much of the day at low SOC which helps reduce degradation. It would have been worse if they charged twice a day. The cars don't have many EV miles on them. If they charged them more to get more EV miles, degradation would have been worse. When it is hot, you are much better off running in hybrid mode vs EV mode to reduce battery degradation. They had four 2013 Fusion Energi's that were each driven approximately 100,000 miles in 1.5 years. The battery degradation was about 8%. They also had four 2013 Volts that were each driven approximately 125,000 miles in 3 years. The battery degradation was about 9%.

This is from the Nissan LEAF owners manual: The capacity of the Li-ion battery in your vehicle to hold a charge will, like all such batteries, decrease with time and usage. As the battery ages and capacity decreases, this will result in a decrease in the vehicle's initial mileage range. This is normal, expected, and not indicative of any defect in your Li-ion battery. Nissan estimates that battery capacity will be approximately 80% of original capacity after five years, although this is only an estimate, and this percentage may vary (and could be significantly lower) depending on individual vehicle and Li-ion battery usage. Note that the battery chemistry in the LEAF, Volt, and Energi and all similar. For the Energi, the original usable capacity of the HVB is 7.2 kWh. 80% of that is 5.8 kWh. The car will not allow you to discharge the HVB below 1.0 kWh. In addition, the car generally charges the HVB to between 97% and 98%. The maximum amount of energy you will get out of the HVB at 80% of original capacity is approximately 4.6 kWh. The following table indicates the approximate amounts of energy you will get out of the HVB for various degradation levels: 0% - 5.9 kWh 5% - 5.6 kWh 10% - 5.3 kWh 15% - 4.9 kWh 20% - 4.6 kWh 25% - 4.2 kWh 30% - 3.8 kWh I am at 5% - 5.6 kWh after 3 years. Also note that the Leaf has a 30 kWh battery, which is four times the size of the Energi's HVB. The Energi has to struggle four times harder to provide the same power as the LEAF. For example, if you drive in EV mode on the Freeway, the Energi HVB will have to struggle much harder than the LEAF to maintain 70 mph. Thus driving in EV mode on the freeway degrades the Energi's battery significantly more than it does the LEAF's battery driving 70 mph on the freeway. In the case of the Tesla, driving on the freeway causes a discharge rate of a small fraction of 1 C. On the Energi, the discharge rate required to maintain that speed is closer to 2.5 C. Driving the car in EV mode on the freeway causes far more degradation of the HVB in the Energi than the Tesla. The Tesla battery barely notices the difference in power requirements required to drive 0 mph vs 70 mph. At such high discharge rates, the Energi battery needs a rest once in a while so that it can keep up with the power demand. The HVB in the Energi was never meant to be replaced. It is supposed to last the lifetime of the car. Replacing the HVB is cost prohibitive. You would never begin to recover the cost of the replacement in fuel savings.

That's for your protection in case you accidently forget to turn the car off when you park it in the garage. You don't want the ICE to start in the garage after the battery is exhausted and have everyone inside the house be exposed to possible CO poisoning.

I traced the source of the rattle in my trunk to the Sony Amplifier on the right side behind the trunk lining. I attached a Bunge cord to it to keep it from rattling. I have no more rattles.

How can you compare the noise levels generated by the ICE between the Volt and the Energi if you don't start the engine? :) Your warranty will run out and you don't even know if it works. Do you know if there is much difference in their noise levels or if active noise cancellation is a significant improvement?

What happens in the winter time when the temperature falls in the low teens or below zero? The ICE would come on in the previous generation of the Volt when the temperature was below 15 F. Have they changed that. How low does the temperature have to go before the ICE will start in the 2016?

The internal charger in the car controls the charging rate--it can charge at any rate it pleases. The pilot signal to the EVSE tells the EVSE the maximum amount of power that the charger will draw. The duty cycle of the pilot signal that the car sends to the EVSE is 50%, indicating that it will draw up to 1/2 the maximum power that a Level 2 EVSE can provide. The car does taper off charging power during the last five to ten minutes of charging. The internal charger will also charge the HVB at a slower rate when the HVB is extremely cold, and probably when it is extremely hot. When Value Charge is selected, they could program the internal charger to use an optimal charging profile, varying the charge rate as necessary, and giving preference to the lowest cost electric rate windows, to minimize degradation to the HVB, just as long as the car is fully charged by the next GO time. In another paper, they claim a Lithium-ion battery should not be operated at a level lower than ~25% SOC (This includes Hybrid Mode in our car. When MyFord Touch states the SOC is 0%, the actual SOC of the HVB is around 20%. In Hybrid Mode, the battery SOC ranges between 15% and 20%). "If lithium ion cells are discharged or operated at a level lower than ~25% SOC, their efficiency and performance is degraded, plus significant heating and aging will occur". So if you have a long commute, it might be advisable to stay out of Hybrid Mode until the end of your trip. Also, you probably don't want to leave the HVB SOC at less than 25% SOC for too long (This corresponds to about 5% as reported by MyFord Touch).

There are two reasons why the SOC of the HVB changes from the value it was when you turned off the car. 1. The SOC of the HVB is determined by the equilibrium voltage of the HVB. The battery needs to rest for an hour or so before coming to equilibrium. Then the voltage can be measured and the HVB SOC can be computed accurately. When the car is running, the voltage of HVB fluctuates wildly and cannot be used to accurately determine HVB SOC. Instead, the car has to estimate the SOC based on the amount of energy it believes is in the HVB. Unfortunately, the car cannot precisely determine the amount of energy in the HVB either (but it provides a better estimate than voltage). So the SOC estimate that it computes while the car is running is going to be a bit off. You will see this estimate when you park the car at work. After the HVB has rested for a while, it can make a voltage measurement and compute an accurate SOC. Thus when you leave work, you see the corrected/accurate SOC. 2. When the battery cools down, it radiates energy. This energy is no longer available to propel the car. The difference in energy in the HVB from when you park the car to when you leave work is the amount of energy that has been radiated. This is reflected as a lower HVB SOC. Ford needs to provide better software to manage the HVB. If I could tell the car the SOC I wanted the HVB charged to each morning, then I wouldn't have to charge to 100%. I only need about 66% SOC to get to work and back. That would help reduce degradation of the HVB. In another paper, they compare battery life with optimized charging plus charging only to the SOC which is needed for the day's driving vs. just plugging in at night and charging to 100%. The battery life in the later scenario was 5.5 years. In the optimized partial charging scenario, battery life was 12.8 years. A very significant difference. They could at least use optimized charging where the car figures out the optimal rates and times to charge rather than simply charging at the maximum rate during the least cost time windows for electricity.