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Drive time vs Charge time

Discussion in 'Model S: Driving Dynamics' started by David99, Mar 9, 2017.

  1. David99

    David99 Active Member

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    One of the few drawbacks of an EV is still the time you spend charging when taking longer road trips. I've driven about 50k miles on Superchargers doing longer road trips and thanks to Teslafi.com I was able to keep track of drive time vs charge time on a recent 4000 mile road trip.

    Adding up the numbers it shows the ratio between driving and charging was almost exactly 1:2. In other words, for every hour of driving I spent 30 min charging.
    The average leg between Superchargers was 117 miles
    The average drive time on each leg was 1h 32min
    The average charge time at each SuC was 45 minutes.
    The average charge speed was 158 mph
    (car: Model S 85)

    My average drive speed was 78 mph. It was cold, so the heater used up additional energy. I think the average energy consumption was around 380 Wh/mile. Driving in warmer weather would give slightly slower energy consumption and save some time charging. Driving slower would change the ratio. Slower driving uses less energy and causes shorter charge times, but it also causes longer drive times. While driving slower makes the ratio between charging and driving look 'better', it doesn't help with the overall time. I found that 70-80 mph is roughly the sweet spot to get the overall fastest trip time.
    At first, the charge speed seems rather low considering that the Supercharger tells you you are charging at 300 mph when you plug in. That's only the charge speed at the beginning when the Supercharger charges at full speed. Over the charge session is slows down quite a bit. It also used 'rated miles' which is unrealistic, especially when you drive faster on freeways.

    Bottom line is actually sobering. That's a lot of time charging!
    Trying to replicate the trip in EVTripplanner.com to match my driving speed and temperature I get a ratio of 2.4. So why is it off? I noticed that the EVTripplanner calculated the drive time and energy consumption pretty accurately. The charge times were off, though. That's something I also noticed with the car's trip planner. It always underestimates the time it takes to charge. I always have to charge longer than what the car tells me and that means I spend more time charging at a lower rate. Also the low temperatures eat up energy that cause longer charge times. Doing the exact same trip in warm weather would use 10-20% less energy thus saving time on charging while keeping the same drive speed. One way or another, I think for road trips the charge times are a big time killer. Hopefully Supercharger 3.0 and better batteries will help.
     
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  2. wdolson

    wdolson Supporting Member

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    Taking trips in warmer weather makes a big difference in energy usage. On my trip to California in October I averaged 309 Wh/Mi. I thought the superchargers were a little too close together for an 90D on many legs, though Tesla is putting in more superchargers along the I-5 corridor that will help longer legged cars. I ended up stopping to charge at 150 miles because that's about where the superchargers were, when around 200-250 would have been more efficient.

    I didn't sandbag any on the speed. I drive just as fast as I always did (probably around 75 mph average, possibly a little higher).
     
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  3. BizJet

    BizJet Member

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    One critical detail is missing from your report, and that is what your strategy is for charging -- that is, what is the average state of charge (%) when you decide to charge, and what is the average SOC when you finish with the Supercharger?

    My understanding of the supercharger performance curve is that optimal charge:drive ratio is achieved when you: start at 100%, charge only when the SOC is low, and (this is critical) only charge to, say, 75% charge. In other words, more partial charges are better than fewer full charges.

    So I'm curious...to what average SOC did you charge in order to get that ratio?
     
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  4. GSP

    GSP Member

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    @David99,

    Thanks for the informative post. 45 minutes seems high for an average charge time. Perhaps a different strategy would help. Do you start your day with 100% charge? This will require less charging on your trip. Also, are you using range mode? Range mode uses waste heat from the motored and inverters to help heat the cabin. Using the heated seats and steering wheel, you also can be comfortable at a low cabin temperature and fan speed settings. 19" LLR tires at 50 psi also help reduce charge time needed.

    I usually have a lunch stop that is one hour or slightly longer (and let my MS charge to 100% if I am not done eating first), and just stop for 10-15 minutes for my other supercharger stops. I have not had to wait for charging yet, the car is always ready before my wife and I are.

    GSP

    PS. I have an S85D with factory 19" Michelin tires. I use TTAC or autopilot at the speed limit or usually +5 mph.
     
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  5. bob_p

    bob_p Active Member

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    On our trip from Houston to Denver last year, we planned for around a 3 to 1 driving time to charging time ratio.

    The longest charging times were due to three legs that had long distances between chargers - 142, 155 and 167 miles - forcing us to charge above 80% before leaving the SC, slowing down the charging. And despite the longer charge times at several SCs, due to weather conditions (strong headwinds) we had several legs when we had to slow down below the posted speed limit to reach the next charger.

    What helped minimize the wait time was stopping overnight at a hotel with a supercharger (getting a full charge there) and stopping several times for meal breaks, when we allowed the car to get more charge than was needed during those stops.

    We found the breaks made the drive less stressful, breaking up the long periods in the car with time to get out of the car, stretch our legs, check our e-mail, hit the restrooms, and get something to drink or snack on.

    Based on our Denver trip experience, we plan to make a trip from Houston to LA in the next year or two. Though that trip will be with our new S 100D. With 70 miles of additional rated range, that should help reduce charging times by keeping charging below 80% and reduce the need to slow down between chargers.
     
  6. thefortunes

    thefortunes Member

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    #6 thefortunes, Mar 10, 2017
    Last edited: Mar 10, 2017
    Interesting. When we drove the car home from California (2400 miles) we drove 34 hours and only needed to charge 11 hours (22 SuC, so ~30 minutes per SuC). This was in September, so we were using A/C vs heat, but otherwise we also typically drove 75-80. We used 795 kWh for an average of 331 Wh/mi.

    We definitely "rode the bottom" of the battery, so possibly the combination of that and your higher kWh/mi account for your 50% higher charge times?

    Note: You can use EVTripPlanner to simulate different speeds, SOC levels at SuC arrival, etc... Since this was a long trip in a short time frame (a weekend) I wanted to figure out the best combination of speed/time charging. On our route it worked out to about 1.1x speed limit - any further drive time reduction was offset by longer charge times required.
     
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  7. ecarfan

    ecarfan Well-Known Member

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    David, thanks for your post. My experience differs from yours. My driving/charging ratio is over 3:1. My strategy is to arrive at a Supercharger with a SOC below 20% and my average highway speed around 70. I recommend you try that approach and see if it significantly increases your driving/charging ratio. You will in fact arrive at your destination sooner compared to going 80 and spending 30 minutes charging after an hour of driving, which means you likely arrived at the Supercharger with an SOC over 50%.

    NOTE: You said your "ratio between driving and charging was almost exactly 1:2. In other words for every hour of driving I spent 30 min charging".

    The way your wrote that sentence, the ratio should be written as "2:1" not "1:2", since you wrote "driving/charging ratio".

    After 56K miles and over 3 years of ownership, my lifetime wH/mi figure for my S85 is about 320. Your 380 figure is likely primarily due to your average speed of nearly 80, well over the speed limit. I recognize that in Southern California doing 80 on the freeway is not unusual...if you can find an uncontested freeway. ;)

    I acknowledge that with an EV a road trip takes somewhat longer than with an ICE. If someone has the mindset that they absolutely do not want to stop except to pee and "gas up" their vehicle than an ICE beats an EV every time. I have never been that kind of driver. Every hour or two I like to stop for at least 5 minutes and walk around a bit. I do not like to sit in a car for hours on end. So when on a road trip with my S, I might make a brief stop for a walk around even if there is no charging opportunity. I welcome a half hour stop to Supercharge but try to make sure that my SOC is low so that a charge stop only takes half an hour. If you start Supercharging at 50% SOC or more your charge rate will be slow.
     
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  8. T Dawg

    T Dawg Member

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    I land in Chicago at 9am CST today March 10th. I will be driving my new (New to Me) Model S P85 from Chicago to Topeka, KS to day. I currently plan on taking I 55 south out of Chicago to I 70 and I 70 west to Topeka. I will then finish the second leg of the trip from Topek, KS using I 70 to I 25 north into Fort Collins, CO. I have downloaded The Teslab app as well as the Tesla app. I will report back my traveling experience using the SC network throughout the trip.

    If anyone has any advice and or suggestions please feel free to shout them out!!!!
     
  9. MorrisonHiker

    MorrisonHiker S 90D 2017.34 2448cfc

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    Make sure you get plenty of charge in Hays before heading to Goodland. Later this year, there should be a Supercharger in Colby to make that stretch easier. I had no problem in my S90D in December but a friend in an S60D had to slow way down in order to make it.

    Enjoy the trip!
     
  10. David99

    David99 Active Member

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    #10 David99, Mar 10, 2017
    Last edited: Mar 10, 2017
    I guess I forgot to mention that I do make sure I arrive at a long state of charge to take advantage of the faster charge rate at lower battery levels. I typically arrive at 5%-15% and only charge as much as I need. I actually posted about this strategy a while ago ('How to save time on long road trips').

    @ecarfan My lifetime average (110k miles total) is 321 Wh/mile. Around town and normal driving I get 300, on road trips usually 350, when it's cold and I go fast, the usage can be over 400 sometimes. This last road trip was definitely on the higher side. I have done this same trip about 8 times and this was the highest energy usage out of all. The lowest was in the summer at 310 Wh/mile also going rather fast, but I had my aero disks on. What a difference they make!!

    So yes this example was probably a worst case.

    Since I don't have good data from when my car was new, I don't have good evidence, but I have the feeling the charge rate at Superchargers has become a little slower over time. It seem the charge rate drops earlier and lower now than it did when the car was new. I'm pretty envious of the new batteries that sustain a higher charge rate much longer and thus overall charge much faster at Superchargers.

    It's a little OT but I have watched the battery temperature during Supercharging and the way the power is reduced has very little to do with the actual temperature of the battery. It's more a hard programmed curve with very little adjustments to real world conditions. Evidence shows that fast charging doesn't hurt the battery. In fact people that Supercharge frequently seem to have less battery degradation. If Tesla would allow a higher charge rate and adjust more to actual battery conditions, all the old 85s would be able to charge quicker.
     
  11. David99

    David99 Active Member

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    Same here, I was actually in a time crunch so I pretty much drive those 2000 miles in one go. And yes going faster than 80 makes the charge time go up quite a bit and offsets the time saved. What lead to such a low charge vs drive time in my case was definitely the cold weather. It sucks up energy without any gain in speed or otherwise. Cold air is more dense so it increases air drag. I also had strong head winds for about 1/3 of the trip which further eats up energy that causes longer charge times.
     
  12. wdolson

    wdolson Supporting Member

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    Some of the slowdown in supercharging may not be your battery, but may be the supercharger itself. Some superchargers, especially in California have seen lower charge rates because they have degraded from overheating. Many get used so heavily they don't get a chance to cool down between uses and the components age much faster.
     
  13. SFOTurtle

    SFOTurtle Active Member

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    My experience is also quite different. I was carefully tracking times on my two latest road trips taken in a 2013 MS 85, and both had far less charge time.

    In January, with a fully loaded car (5 people), we drove from Anaheim to Los Altos and back. Actually drive time was about 6 hours and 15 minutes both ways timed so that we didn't hit traffic in LA. Charge time on the way down to LA was about 2 1/4 hours but one of those stops was a full dinner stop at Tejon for 75 minutes, about 30 minutes longer than we'd normally stop. On the return north from Anaheim, we stopped at the iHop in Buttonwillow for brunch for about 50 minutes and then at Harris Ranch for about 50 minutes again. We made it home without stopping at Gilroy about 5 rated miles, but I have enough experience with the car when to stop at Gilroy and when not to, and how fast I can drive the last 30 miles to get home with a few rated miles at the worst. Experience helps.

    My last trip was from Seattle to Los Altos on Feb. 25. Temps were in the low 30s when I left Seattle in the morning, but otherwise weather was in the 40s most of the way. Drive time was 12 hours. Charge time was 4 hours and 15 minutes. I easily could have shaved 15-30 minutes off of the charge time if I had a little more experience with the route and if I hadn't tried to bypass Corning on the way from Shasta to Vacaville. I wasted about 15 minutes trying to get to 90% charge, but in the end I wouldn't have had enough to bypass Corning anyway because of the cold temps around Shasta and headwinds once I got south of Redding. Also, I overnighted in Seattle at a friend's house where I couldn't charge the car and began the trip from Seattle with only about 50% SOC. I had to nurse the car a little bit into Centralia because of the cold temps, and I had to charge longer in Centralia because I arrived with only 12 rated miles. If I had started the trip with a full charge, then charge time would certainly have been less than 4 hours.

    Even in the worst case when we drove back from LA in November 2015 with a fully loaded car in severe Santa Ana headwinds that required 90%+ SOC to leave for the next Supercharger with some degree of confidence, our charge time was still only 2 1/2 hours on a 6+ hour drive.
     
  14. Nosken

    Nosken Member

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  15. David99

    David99 Active Member

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    It is. And it shows that the charge time vs drive time ratio is actually exactly what I experienced going at the speed I was going at and adding in extra energy usage from cold weather.
     
  16. T Dawg

    T Dawg Member

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    Ok, so here is my experience after flying into Chicago and driving the 2013 Model S P85 (OD 24K miles) back to Fort Collins, CO. First, I'd like to give a shout out to D&M Motorsports in Glen Elyn, IL for such a smooth process throughout the purchase. The car was everything and more than I expected. I had the detail shop attached to the dealer apply the Modesta BC-04 & BC-08 to the complete exterior, including wheels. I also had the interior treated. The care is flawless!!!

    Now onto the trip. The car was fully charged when we (father-n-law in tow) picked it up. We were determined to drive the car just like we would any other car. Triple A membership was paid in full just in case. Note: I was not going to save the world by driving 55mph just to be the most efficient.

    So, we headed out of Chicago due south on I55 towards St. Louis rolling at 75-80mph. We hit the Bloomington, IL supercharger. The supercharger was somewhat off the beaten path, located in a parking garage. Not a huge deal as we found a local eatery to have lunch while we waited. Less than an hour later we were back on I55 south to St. Louis. Next stop was at supercharging station located next to a Scheels Sporting Goods in Springfield, IL. I had never been, so my father-in-law and I took a tour around the store while the car charged. Less than an hour later we were headed to St. Charles, MO (west of St. Louis). Arriving at the St. Charles supercharger, we found that there was a Smashburger located right there. So we had dinner while the car charged. Again, less than an hour later we were on our way at I-70 west to Topeka Kansas. Next stop was in Columbia, MO. We had already had enough to eat so we hit the supercharger while staying in the vehicle, less than an hour later we were on our way to Independance, MO. This would be the last supercharger visit before Topeka, KS. We arrived in Topeka around 1:00am.

    I spent the next day idle prior to making the second leg of the trip to Fort Collins, CO. While in Topeka, I used the only supercharger there, just off of I-470. The coolest thing about hanging out at a supercharger is meeting other Tesla owners. Not a one didn't strike up a conversation centered around the experiences in owning such an incredible machine....it is a cult and I very much enjoy it!

    Sunday I was up and attem. I had got a complete charge the night before, so I hit the road straight west to Salina, KS. I hit the first supercharger of the day at a local hotel only to see that 3 of the spots being occupied by minivans. I didn't realize that Tesla had already released a minivan model. . Nonetheless, less than an hour later I was on the road and headed to Hays, KS. I grabbed a burger at a nearby Wendy's while the car charged. Next stop was Colby, KS. Along the way to Colby, I started to get a lot of looks as people passed me. Some of which were taking videos and pictures. I'm sure I was a part of the social media world and text messages to their friends. Felt like a rockstar for a few moments. Nonetheless, I was in Colby in no time, got a good charge and headed right off to Goodland, KS. I spent less than 40 minutes in Goodland and headed out to Limon, CO. By this time, the wind was picking up and I was being pushed around a bit. I slowed down to 70mph as there was a lot of semi tractor trailers on the road. I charged in Limon while eating at the Arby's just off of I70. I spent a full hour or more charging as this would be my last charge before I reached my home in Fort Collins. Since being home, I charge at the Loveland, CO supercharger. I will be relocating to California at the end of March, so no need to waste installing my home charger prior to the move.

    For the trip, I downloaded the Teslab app prior to the trips. Below are my stats:

    Total Miles Driven: 1280
    Drive Time: 21 hours 11 minutes
    Avg. Speed: 64.8
    Charge Time: 8 hours 28 min
    Superchargers Visited: 11
    Efficiency: 68.33%
    Longest Leg: 128 miles
    Outside Temps: 28-35 degrees most of the trip...last leg home was mid 50's
    Winds: strayed around Limon, CO and continued to the DIA area, gusts were reported to be out of the north at 45mph.

    Sorry if this rant bored the majority of you. I did not experience much if any "range anxiety" because the navigation screen gave me all of the information I needed to make each leg of the trip. Also, I purchased a Tesla because of how incredibly interesting the whole EV concept is coupled with the raw power and luxury the car exhibits. I will be moving to California where Tesla owners can get into the HOV lanes without having a passenger....speeds up the commute "somewhat".....again "somewhat".

    Lastly, I have been fortunate to experience owning several sports cars over the years, I will Tesla hands down outperforms them all. I hope to continue to experience all the good things that the car and the Tesla community has to offer for years to come!
     
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  17. bishoppeak

    bishoppeak Member

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    Great writeup! You probably spent a lot more time charging than you needed to, but had the proper attitude about it. I'm sure you'll get more "efficient" when you're here in CA. Glad you enjoyed your trip.
     
  18. ShockOnT

    ShockOnT Quickish

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    Charge rate is much faster when battery is less that 50%, so only charge enough to reach the next supercharger, not to 100% (unless you're eating or sleeping or otherwise happy to keep charging).
     
  19. T Dawg

    T Dawg Member

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    Is this a fast supercharger?
    It didn't take long to get a full charge!
     

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  20. ig_epower

    ig_epower Member

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    I would say yes. Anything over 90 KW is a great rate IMHO. I have experienced up to 120 KW assuming you have 15% SOC or lower to start with. I pity the people that have to suffer from low rates like 20 - 30 KW because they are the slave connection to another paired Tesla that came before or due to a limping charging station due to maintenance issues.
     

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