larryh

Note that in the simple analysis in the previous posts, the SOC and temperature difference effects on degradation were not taken into account. The analysis only considered the effect of an increased charging rate on degradation. The amount of degradation due solely to charging at a high rate for 2 hours vs. charging at a slower rate for 6 hours is small. Too close to call to be certain which is better. However, because Level 1 Charging starts four hours earlier than Level 2 Charging, at any given time, the SOC of the battery will be higher with level 1 Charging. After 4 hours of Level 1 Charging, the HVB SOC be at 73%. For Level 2 Charging, we will just be starting to charge the battery (SOC will still be at 20% assuming the HVB SOC started out at 20% SOC). Higher SOC means higher degradation. As a result of the higher SOC for the Level 1 Charging profile, the increase in internal resistance due to degradation of the battery will be about 1.8e-5 Ohms greater with Level 1 Charging vs. Level 2 Charging if you go through the math. We also need to take into account the effect of the temperature differences in the two charging profiles on degradation. With Level 1 Charging, the temperature of the HVB will increase at approximately a constant rate for the entire six hours. With Level 2 Charging, the HVB will continue to cool down for the first four hours, and then the temperature will rise at an accelerated rate for the last two hours exceeding the final temperature reached during Level 1 Charging by perhaps up to 5 F (being generous). I don’t have any data on internal resistance degradation vs. temperature so I can’t do a thorough analysis. However, I can easily compute the average temperature for the two charging profiles. It is going to be lower with level 2 Charging, simply because the battery is cooling down perhaps a degree during the first four hours and then begins rising only during the last 2 hours. During most of that time, the HVB temperature will be less with Level 2 Charging than Level 1 Charging except during the final hour (and then it will only be a few degrees higher). So most likely Level 2 Charging again will result in less degradation.

The numbers provided are only gross approximations based on my best guesses from the graphs provided in the papers. I had to make many assumptions to come up with them. Tweaking the numbers I used isn't going to provide any useful answers. The actual computation is very complex, solving a set of differential equations using numerical analysis. The author's in the papers already did this much more precise calculation incorporating additional factors such as temperature and battery cycling. They determined charging at a faster rate caused less degradation. I have no way of verifying their more precise analysis. The point of my post is simply to illustrate that even though faster charging causes faster degradation, this degradation occurs for much shorter period of time resulting in less overall degradation than slower charging (that was the point made in the papers). The calculations were 0.22e-8 Ohms/s * 6 hours * 3600 s/hour = 4.8e-5 Ohms and 0.63e-8 Ohms/s * 2 hours * 3600 s/hour = 4.5e-5 Ohms/s. The difference between the two is going to be small and as I mentioned, I don't have anyway to improve the accuracy of these calculations and come up with the correct answer for the Energi's HVB.

You can also set the value charge windows to indicate a high electric rate to avoid charging right after you plug in at work (provided you at at work long enough that you can delay charging). My first priority though would be to make sure that the car is not in the hot sun. The can easily cause the HVB temperature to rise above 100 F.

The following plot shows battery degradation at room temperature of the Li-ion battery in the papers of the previous posts as a function of SOC. The Blue line is the degradation that occurs when the battery is not being charged in 10e-8 Ohms/second. The red line is the degradation rate for a Level 1 Charger and the green line is the degradation rate for a Level 2 Charger. Degradation increases rapidly with increasing power applied to charge the battery. Degradation decreases with increasing power discharged by the battery to at least several kW and then begins increasing again very rapidly. So charging the battery increases the battery degradation rate above and beyond the normal degradation rate that occurs while the car is off. In this case, the Level 1 Charger increases the degradation rate by 0.22 x 10-e8 ohm/s and the Level 2 Charger increases the rate by 0.63 x 10e-8 ohm/s. The total increase in resistance due to charging the battery with a Level 1 Charger for six hours is then 0.48 mOhms. The total increase in resistance due to charging the battery with a Level 2 Charger for 2 hours is 0.45 mOhms, i.e. slightly less. So in this case, the additional degradation caused by charging the battery is less using the Level 2 Charger. Even though degradation occurs at a much higher rate with the Level 2 Charger, we are charging the car for much less time, so total degradation is less. We have no way of determining the actual difference for the HVB in the Energi. So it is entirely possible that using a Level 2 Charger will result in less battery degradation, provided you only charge the battery with it just before you leave. If you don't want to go to the extra trouble to only charge the HVB right before you leave, you would be better off with the Level 1 Charger--it can't charge the car as fast so the average daily SOC will be lower vs. the Level 2 Charger resulting in less degradation. Note that according to the chart below, degradation occurs 8% faster when the battery is at 60% vs 30% SOC. So it could be advantageous to leave it at a lower SOC than 60%. Also, the SOC reported by the car is not the true SOC of the HVB. The actual SOC is higher. When the car says the SOC is 0%, it is really about 20%. I wouldn't worry about the fans. The vast majority of the heat generated is from the car's internal charger itself, not the battery. When attached to a Level 1 charger, 20% of the energy is lost as heat by the charger. For the Level 2 charger, 10% of the energy is lost. The HVB itself only converts about 3% of the energy to heat. The fans running a high speed is a good thing. It will help cool down the HVB quicker.

There is no way for us to determine the optimal charge profile for charging the Energi’s HVB. For the battery under investigation in the papers, the optimal charge profile was not a constant rate, but a gradually increasing charge rate maxing out at about 5 kW ending just before the start of the morning commute. If we restrict charging to constant rates, then the optimal constant charge rate is 6.6 kW. However the battery life difference between these two profiles was only a couple of days (below the level of uncertainty of their models). So either one is a good strategy. The Energi’s HVB is a different size and uses a different chemistry versus the one in the papers. So the optimal charge rate for the Energi’s HVB is unknown. The only thing we can be certain of is that delaying charging until the last possible moment is better than charging sooner. MyFord Mobile allows us to enter GO Times and the Time of Day electric rates. Ford should also use this information to minimize HVB degradation. The user should be able to plug in the car and then the car could determine the optimal charge profile to minimize electricity cost and simultaneously minimize HVB degradation, ensuring the car is fully charged by the next GO time. The battery is very expensive. Each time you charge the HVB, it degrades a little more. There is a cost associated with this degradation. Eventually, you are going to have to replace the battery when it degrades too much. I would rather pay a little more for electricity if it saves me from having to replace the battery. It may be better to delay charging to a time when electric rates are more expensive if it significantly reduces degradation of the HVB. It may cost me an extra $1 to charge at the higher rates, but the additional degradation caused by charging in lower cost electric rate windows may be $10. The user should be able to plug in the car at any time and the car will take care of the rest to minimize my overall cost. If properly implemented, this could significantly increase the HVB lifetime by years.

In the papers in the previous post, the end of life of the battery was declared when either the capacity fell below 80% of the original capacity, or power fell below 90% of the original power. However, the papers assumed a different battery chemistry than the Energi’s HVB and also they assumed a 30 kWh battery (4x the size of the Energi’s). Further they assumed the battery is charged only at night and made simplifying assumptions how the battery was discharged during the day. They took into account degradation of the battery due to SOC, Temperature, and Cycling effects. You can’t directly apply those results to the Energi’s HVB. The most important conclusion that you can draw from those reports is that you want to delay charging as long as possible prior to your morning commute. That agrees with the chart in my previous post showing the rate of degradation vs temperature and SOC. You don’t want to keep the HVB at 100% SOC any longer than is necessary. They did not investigate the optimal strategy for people that also charge during the day.

Another paper that corroborates the one in the previous link can be found here: http://ecal.berkeley.edu/pubs/JPS_ChgPatternOpt_Preprint.pdf. "Comparing different solutions ... indicates that to effectively minimize battery degradation and energy costs, one should ideally charge a PHEV rapidly, off-peak, and shortly before the onset of road travel". Figure 7 in that paper provides a battery degradation map showing battery degradation for various charge/discharge rates at room temperature. Degradation increases with increasing charge rate, and decreases with increasing discharge rates. The battery degrades orders of magnitude faster during charging (using the charger or via regen) than during discharging (i.e. powering the car) or storage. In addition, degradation is slightly greater during storage than while discharging the battery (i.e. powering the car). When charging at a given charge rate, degradation is significantly greater at both high and low SOC. That is one reason the charger tapers charging when the SOC approaches 100%. Since degradation rates are higher with increasing charge rate, one would think it would be better to charge at a slower rate than a faster one. However: "Figure 12 shows that the optimal charging rate ... is close the maximum rate of 1C. At the first glance, this seems counterintuitive, because from the battery degradation map (shown in Figure 7) we see that the battery degradation rate is higher at higher charge rates. However, it is also evident that by increasing the charge rate we decrease the charging duration. Thus, the high-rate battery degradation process due to fast charging takes place for a shorter period of time. Hence, the resultant damage can be smaller if reducing the total battery degradation due to reducing the charging duration dominates the increase of degradation due to fast charging. The obtained optimal results indicate that this condition holds true, at least within the range of 0-1C charging, according to the employed battery model." The charge rate for the level 1 charger is about 0.15 C and for the Level 2 Charger is about 0.4 C. Both are between 0 and 1C. Hence charging using a Level 2 Charger degrades the battery less than using a Level 1 Charger. For the battery in their study, the optimal charge rate is 1C, which is approximately the full Level 2 charge rate of 6.6 kW. You want to delay charging until the last possible moment and charge the HVB with a Level 2 charger. One additional observation about delaying charging until the last possible moment, is that if you charge earlier, the battery will begin to cool off before you leave. It is loosing energy. So by delaying charging, you maximize the amount of energy available for your commute.

The following link provides information on optimized charging strategies to prolong battery life: http://www.nrel.gov/docs/fy14osti/62813.pdf They considered six different strategies for charging at night. The battery in this study has a larger capacity battery than the Energi's HVB. Note that the Energi HVB can only accept a maximum charge power of 3.3 kWh, i.e. half the full level 2 charging power. For the battery in this study, the battery can be charged at the full Level 2 power of 6.6 kW. 1. Charge on plug-in: charge immediately on plug-in at full level 2 power of 6.6 kW. Battery life was 5 years. 2. Slow charge: charge at a slow, constant rate for the entire night. Battery life was 6.8 years. 3. 8 hour charge: charge at a slow rate for the last 8 hours. Battery life was 7.2 years. 4. Late fast charge: charge at 18 kW during the last hour. Battery life was 6.8 years. 5. Late 6.6 kW charge: charge at full level 2 power of 6.6 kW waiting until the last possible moment. Battery life was 7.9 years. 6. Delayed Charge: charge at full level 2 power of 6.6 kW starting at 12:00 am. Battery life was 6.3 years. The best strategy was 5: Charge at full level 2 power waiting until the last possible moment. Predictably, the worst strategy was 1: Charge at full level 2 power immediately on plug-in. The difference in battery life between the two strategies was 2.9 years (very significant). Strategy 5 is basically what I am doing. Note that 1, 5, and 6 explore when is the best time to start charging at full level 2 power of 6.6 kW. The results clearly demonstrate that delaying charging until the last possible time provides a significant increase in battery longevity: 5 years for charging on plug-in, 6.3 years for starting at midnight, and 7.9 years for waiting until the last possible moment. 2, 3, 4, and 5 explore what is the best rate at which to charge the HVB, delaying charging at that rate until the last possible moment. You want to charge it had a relatively fast rate (5), but not too fast (4). Also, you don't want to charge it too slowly (2) and (3). Basically, you want to delay charging as long as possible and then charge at the maximum charge rate of 3.3 kW allowed by the Energi's internal charger for the HVB.

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries Actually, the degradation at top right of the chart should be far worse than shown. 40% loss occurred in three months rather than one year for 100% SOC and 140 F. However, the HVB in the car should never reach 140 F. The maximum I have observed is 113 F. But if you live the South where temperatures reach 120 F, the battery is going to be at least that temperature. You could always skip charging the battery (at least not to 100%) and use the ICE instead if it gets that warm.

The chart below shows the annual degradation of an older design Lithium-Ion battery at various SOC and temperatures. The battery was maintained at the specified temperature and SOC for a year and then the degradation was measured. Degradation occurs continuously in a Lithium-Ion battery, even when it is not being used. Undesirable chemical reactions are always taking place in the battery that degrade its capacity. The rate of these undesirable chemical reactions are a function of temperature and SOC. The maximum rate of degradation occurs at the top right at high temperatures and high SOC. The minimum rate of degradation occurs at the bottom left at low temperatures and low SOC. The HVB in the Energi should have significantly less degradation under the same conditions as the battery in the chart--perhaps at 1/4 the rate indicated in the chart. But as with the older design battery, degradation increases with increasing SOC and temperature. The white bars illustrate where the HVB in my car spends most of its time during the summer. The car charges from about 3:00 am to 4:30 am in the morning. I then leave for work at about 5:15 am. During this time, the car is at 100% SOC for less than an hour a day. The top bar is where the battery operates during this short period of time: around 90 F and 100% SOC. HVB degradation occurs during this period at a rather high rate, but only for a short period of time. I leave the car parked at work for about 9 hours in the shade of a tree. During this time the SOC is around 66% and the HVB temperature is between 80 F and 100 F. The middle bar indicates the state of the battery during this time. HVB degradation now occurs at a more moderate rate. When I arrive home, I plug in the charger, but have value charge profiles set up so the car does not charge until 3:00 am in the morning. The car sits in the garage for the rest of the day with the HVB temperature between 75 F and 100 F at about 30% SOC. For most of the day, degradation now occurs at a much slower rate. During the spring, fall, and winter, the HVB temperatures are lower--the horizontal bars move to the left. Degradation now occurs at a significantly reduced rates vs. during the summer. In fact, during the winter, the HVB temperature stays below 50 F most of the time. The HVB battery spends practically all its time during the winter in the blue region with the slowest degradation rate. Now consider someone with a long commute that charges at home and at work. However, instead of delaying charging, they charge immediately when they get to work and when they get home. Since they have a longer commute than I, the temperature of their HVB is going to be warmer. Since they charge immediately, the SOC of the battery is going to be at 100% for most of the day. During the summer, their battery is going to be spending most of its time in the salmon colored region at the upper right of the chart with maximum rate of degradation. Their battery is going to degrade four to five times faster than mine. It would be much better if someone with a long commute delayed charging until right before leaving for work or to return home rather than charging immediately upon arrival at work or home. If they did that, the HVB would spend most of its time at the far bottom right corner of the chart where degradation occurs at maybe one-half to one-third the rate it occurs vs. charging immediately. There are other factors that affect battery degradation (such as the number of charge/discharge cycles), but temperature and SOC are the primary factors that impact battery degradation.

Finally, SyncMyRide.com allowed me to download Sync2-V3.8. I now have the latest version of Sync installed. Previously, whenever I logged into SyncMyRide.com, it erroneously reported that my prior version of Sync was up to date.

The car contains many interconnected computer modules. If the wiring is bad or the 12 V battery is low, then they cannot communicate properly. The modules are going to receive bad signals causing unpredictable behavior. Did you have the RCM replaced as specified in one of the recall notices. That can also interfere with communication between the modules.

The following plot shows degradation of the HVB over the three years I have owned the car. I recorded the HVB temperature and the Energy Capacity of the HVB each day for the past two years--I don't have measurements for the first year. There wasn't much degradation during the first year. Each marker represents one of those measurements. When new, the maximum capacity of the HVB was 7.2 kWh at temperatures above 70 F. The car will not let you discharge the HVB below 1.0 kWh to prevent damaging it. If you fully discharge the HVB, it will no longer accept a charge. In addition, the car does not generally charge the HVB to 100% SOC--it usually charges to about 97%-98%. So the maximum energy you can get out of the HVB when it is new is about 7.2 kWh - 1.0 kWh - 0.2 kWh = 6.0 kWh. As the chart indicates, degradation is greater with decreasing temperature. So in the winter, HVB degradation has a much greater impact than in the summer. The blue markers represent measurements made during 2014. At a HVB temperature of 85 F, the capacity of the battery was about 7.1 kWh. During 2015, the red markers, it was about 6.95 kWh. And for 2016, the green markers, it was about 6.8 kWh. The total degradation at 85 F is about (7.1 - 6.8)/6.0 = 5% after three years. [Note since I don't have measurements for the first year, I'm not sure if 7.1 is the correct number to use. The measured capacity could well have been 7.2 kWh during the first year, in which case, degradation would be 7%]. At a HVB temperature of 50 F, the battery capacity was about 7.0 kWh during the first year. After three years, it was about 6.4 kWh at this temperature. The degradation during the winter is about (7.0-6.4)/6.0 = 10 [or again, since I don't have measurements for the first year, it may be as high as 12%]. There is insufficient data for temperatures below 40 F to provide accurate measurements. I currently have 35,000 total and 25,000 EV miles on the car. I charge about once a day using a 240 V charger set to charge at 3:00 am. My commute is 16 miles during the week so I only fully discharge the HVB during my weekend drives. I live in Minnesota.

I purchased the 7/year 75K $200 deductible from Anderson and Koch three years ago. The current price at their site is a little less than what I paid (with the same assumptions): $885 vs $900.

If you go to Ford's web site, you will now see that the 2017 Fusion Hybrid and Energi have the same MPG: 43 city/41 highway/42 combined. For the previous model years, the Energi MPG was lower than the Hybrid: Hybrid was 44 city/41 highway/42 combined. Energi was 40 city/35 highway/38 combined. That was because they measured the MPG for a C-Max Energi instead. It appears for 2017 they are now actually measuring the MPG for a Fusion Energi.

Power output of the Fusion Energi is Limited by the HVB size. It can only output 65 kW of power from a 7.6 kWh battery. The Volt has a HVB twice as large and hence can output significantly more power. The Model S battery is 10 times large and consequently the 5 second 0 to 60 acceleration. Note that the original numbers for the 2013 Energi were 21 mile range, 100 MPGe, and 43 MPG (before the adjustment). The 2013-2016 model year numbers are based on measurements made for the C-Max Energi (they expected it to outsell the Fusion Energi). Since the Fusion Energi far outsells the C-Max Energi, they are probably using the actual Fusion Energi measurements now. The Fusion Energi is more aerodynamic and hence has better range, MPGe, and MPG than the C-Max Energi. In that case, there probably is no significant change in range, MPGE, or MPG between the 2013-2016 model years and the 2017 model year.

Mexico labor costs are $8/hr. US is more than $60/hr. Ford reserves expensive US labor for high margin vehicles like trucks and SUVs. They use the cheaper labor for less profitable mid-sized/small cars.

The plug-in electric vehicle tax credit phases out after 200,000 qualifying vehicles are sold by a manufacturer. With more than 200,000 reservations, people are no longer going to get the full tax credit, and after one year following the phase out period, there is no tax credit. So the Tesla Model 3 is going to be more expensive the other plug-in vehicles.

EV+ applies to any frequent destination regardless if you charge there.

Remote start will be less likely to start the ICE when in EV now mode. However, when temperatures are close to 0 F, the ICE will start.

I usually charge at most once per day except Saturday (I don't usually go anywhere on Saturday with the car). The battery is generally fully depleted twice per week. My commute to work is 16 miles round trip, so in the summer it is only depleted to 35% each day. However, in the winter, it is fully depleted. A 7.6 kWh battery is not enough for my 16 mile commute in the winter. I generally charge the car with a 240 V charger at 3:00 in the morning when the electric rates are low. I have driven 31,000 miles.

The following plot shows the kWh of energy provided by the HVB for my 60 mile commutes for the time I have owned the car collected from MyFord Mobile. During the first summer, the energy provided by the battery peaked around 5.85 kWh. During the second summer, it was around 5.7 kWh. And during this past summer, it was about 5.6 kWh. So the total degradation is about 0.25/5.85 = 4%. However, for the first winter, the average energy provided was about 5.5 kWh. The second winter was about 5.1 kWh. And this winter is appears to be around 4.8 kWh, but it has not gotten all that cold yet. So the degradation during the winter is about 13%. Degradation has much greater impact in winter than summer.

Note that a Tesla Model S battery has far more cells than the Energi's battery. That means each cell in the Energi is doing a lot more work than in the Tesla to propel the car. Also, I suspect that degradation is not uniform with respect to temperature. If you have a 25% loss in capacity at 80 F, you might have a 35% loss at 30 F. from when the battery was new.

See the following article on Lithium based batteries degradation: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries. In that article, they define the lifetime of a battery as the time until capacity drops below 70%. Since the Energi HVB has such a limited capacity, it is going to experience faster degradation than the larger batteries of other EVs. If order to commute to work, most will likely fully discharge the HVB. (Note that my commute is 16 miles, so I discharge the battery to about 35%.) The number of charge/discharge cycles is going to be greatly reduced with 100% discharge: Depth of discharge Discharge cycles 100% 300 - 500 50% 1,200 - 1,500 So essentially, if you only discharge the battery 50% each time, you will get four times as many cycles. That means over the lifetime of the battery, you will get 4*50% = twice the energy out of the battery, i.e. it will last twice as long. But if you only discharge the HVB 50%, your range will be reduced to 10 miles. You are going to have recharge the HVB every 10 miles which is impractical. The following shows the degradation of the HVB stored for one year at various SOCs and temperatures: Temp 40% SOC 100% SOC 32 F 2% 6% 78 F 4% 20% 104 F 15% 35% Don't leave the HVB fully charged, especially when the battery is warm. Ford does nothing to protect the HVB against this type of degradation. It is up to you to do this. Active cooling isn't going to work since the cooling system will be off when the car is not being used. The lifetime is also influenced by how fully the HVB is charged. SOC Discharge Cycles 100% 600 - 1,000 90% 1,200 - 2,000 80% 2,400 - 4,000 If the HVB were charged to only 80% each time, the lifetime could be increased fourfold. With the Energi, there is no mechanism to charge the HVB to a specific SOC as with other EVs. Most EVs such as the Tesla, Leaf, and Volt either prevent you from charging beyond 80% or recommend that you do not charge more than 80%. Because the Energi HVB is so small, HVB degradation is going to occur much faster than in EVs with larger batteries. There is no way getting around the physics of the problem. If you want prolonged battery life, then Ford would have to be more conservative with how they manage the HVB and you are only going to get about 4.2 kWh out of the HVB, or a range of 15 rather than 20 miles. I don't think the Energi would sound as attractive with at 15 miles range vs 20 miles. So battery degradation suffers. So basically, the only way to slow down the HVB degradation in the Energi is to put in a larger HVB and maintain the same range, or limit the amount of range you get from the current HVB. The HVB in the Energi is simply too small. If one is concerned about HVB degradation, they will have to buy a car with a much larger battery for which it is possible to manage more conservatively.

pluginamerica.org also has data for the Nissan Leaf. After 30,000 miles, the average degradation seems to be around 6%. After 60,000 miles it is about 8%. So again, most of the degradation occurs in the first 30,000 miles. The Leaf is air cooled. Comparing the data for the Leaf vs. the Tesla, liquid cooling doesn't accomplish all that much (for most people). I suspect that the small size of the Energi's battery is a factor in the greater degradation experienced with the Energi's HVB. My Energi HVB has experienced 5% degradation after 30,000 miles. It is in line with both the Tesla Model S and the Nissan Leaf. They should have a survey for the Energi so we could determine what I am doing differently to experience less degradation than others. When looking at the Leaf Survey data, all the cars (without exception) with the greatest degradation were from CA, AZ, and TX where it is hot. I am from MN. With the Model S, the worst degradation was around 10%. With the Leaf, it was around 30%. So liquid cooling does probably help reduce extreme degradation in warm climates.