You probably already have a good idea of how long it will take to drive somewhere based on your experience with gas cars. That part shouldn’t be much different with an electric car. The main difference is charging rather than buying gas. You need to figure out
· how often to stop
· where to stop
· how much charge to replenish
· how long charging will take
We will cover those issues one by one below; but before we get in to that, we should have:
A note for EV newcomers
Driving electric has many advantages. Smoother, more responsive, quieter, lower center of gravity, less maintenance, cheaper to own than comparable gas cars, cleaner, use US fuel, and all that. However, fully-electric vehicles do have one disadvantage: road trips take longer. That is because charging is slower than refueling - which doesn’t matter for everyday use where you charge overnight in your garage, but can be a drag on a long drive. Fear of this situation is why many people are sticking with gas cars, and missing out on all of the electric advantages.
However, a disadvantage is not really a disadvantage if you never encounter it – and all-electric road trips are REALLY easy to avoid. First, you can always buy a plug-in hybrid (PHEV), which will electrify most of your driving but still has a gas engine so road trips are unchanged. It doesn’t get any simpler than that.
You may prefer an an all-electric car (less maintenance, more range, better packaging and less cost than a comparable PHEV), and that's fine because there are still many ways to avoid having to plan an electric road trip. You could take a second family car, rent or swap a car, fly/bus/train, etc. Buying an electric car does not require you to sign a pledge saying you will never use any other form of transport. Not only do many plug-in owners never take a road trip in an all-electric vehicle, but many plug-in owners never charge their cars anywhere other than in their own garage.
Even though you don’t have to take an all-electric road trip, you may find that you want to. Gas cars are noisy, they vibrate and jerk as you accelerate, the accelerator is not nearly as responsive, gas is expensive and dirty while the solar-powered Superchargers are free…this post is optional reading for those owners that choose to take a long electric trip.
[Pic: my Seattle-based Roadster in San Diego, April 2010]
[Pic: my Model S in Death Valley, January 2013]
How often to stop
The key rule-of-thumb is to never plan to drive farther than 2/3 of your EPA range without charging (although you may alter that plan slightly as you are taking the trip depending on conditions). That’s 177 miles in an 85kWh, 139 miles in a 60kWh, and 95 miles in a 40kWh. For simplicity I will assume an 85kWh car in this post.
There are many details behind the 2/3 number HERE. With that information you can make some adjustments for a specific trip; but the simple rule of thumb that should cover the vast majority of cases is to not plan your charging stops any more than 177 miles apart. While you may go much farther than 177 miles if you drive slowly on a nice day (300 miles really IS possible), surprise bad weather - including headwinds on an otherwise nice day - could bring your range way down even if you drive conservatively. And when weather conditions are good, the Model S makes it hard to drive slow – but faster driving uses a lot more energy.
Planning more frequent stops is more work, so most people grumble about limiting trip legs to 177 miles. They grumble even more when I point out even that may sometimes be too far. What if the charger is broken or blocked? You should always leave a buffer for that. Shorter trip legs with more frequent charging:
· keep you from worrying if you will reach the next charger or not
· keep you from having to slow down or turn off the climate control
· give you a lot more options if you run in to a problem with the next charger
· keep your battery closer to the middle where it is most comfortable
· give you more breaks from driving (177 miles is 2 - 3 hours; a break is a good idea anyway)
· help keep any single break from getting overly long
You can always skip (or more likely, cut short) a planned charging stop if conditions are good and you don’t need it. But plan for it anyway. I tried stretching my range on my first long trip, and had several problems. I learned my lesson and don’t do that anymore; I have since taken 5 long trips (1,600 to 3,000 miles each) with shorter legs and have had no issues – the trips are much more enjoyable that way!
Where to stop
Inside your 177-mile range, the primary thing that determines where you make a charge stop will be is the availability of the fastest charger you can access. If you need a reminder of what types of places you can plug in to, what you need to use them and how fast they are, there is a list HERE.
If you have more than one charging site to choose from, you should take in to consideration what you can do at each location while charging. There is no point to just stand around and wait for your car to charge, so look for things you’d like to do anyway – visit friends, go to a museum, watch a movie, eat, spend the night, read, get some exercise, check email, etc. Charging time is not wasted time if you are doing something you want or need to do. Is the charging location protected from the weather? Are there restrooms, internet access, walking paths or parks nearby? Are there other chargers nearby in case there is a problem with the one you plan to use?
If you happen to be on the US West coast, HERE is a map that shows you Tesla Superchargers, high-amp J1772 stations, and Roadster HPCs as well as a few “strategic” 14-50 outlets and low-amp EVSEs. You can also use EVSE-finder sites like the following (this is not an exhaustive list; just some sites that I happen to use. No one site has every option):
· recargo.com
· carstations.com
· chargepoint.net – the first charging network to include chargers outside its network. Includes station status for Chargepoint stations
· plugshare.com – originally a network of owner outlets, now includes public outlets too - so perhaps the most comprehensive overall
Plus you can look at any number of campground directories that list campgrounds with 50-amp electrical service. (Be sure to ask for “50 amp”, not “240 volt” or “NEMA 14-50” which often cause confusion).
How much charge to replenish
The simplest method is to reverse the 2/3 leg-length mantra, and to say that you will charge until you have at least 150% of the miles necessary to reach the next charging point. At least 150% - you really should add an extra ~25 miles in case there is a problem at the next charger and you have to drive to charge somewhere else. For example, if it’s 100 miles to the next charger, you should not leave your current charging station until your car says you have 175 miles of rated range. That may seem like a lot, but just think how nice it will be to take that drive with no worries about getting there! Besides, unless it’s your last charge of the day, any leftover charge will save you time at the next stop anyway.
If charging conditions are ideal, you may want to stay even longer as having more charge is always better. Well, always better up to the full 240 miles in Standard Mode, anyway. Tesla does not recommend frequent Range Mode charging and charging is slower in Range Mode, so only wait for that if you need it to reach the next charger – or if you are hanging around anyway (i.e. spending the night) and want to use the idle time charging to save time on your next charge. For example if you are at the fastest charger on your trip, and nobody else is waiting for it, and you have things to do there…well, stick around and charge until 240 miles. But if you get bored, or the next charger is faster, or somebody is waiting for this one, you might want to leave as soon as you get to 150% of the miles needed to make the next charger. Perhaps a little sooner if the weather and road conditions are favorable and you don’t plan on going fast; but you should have some road trip experience under your belt before you try that.
The above describes when you have enough miles to leave. To make an estimate of how many miles of range you will have when you arrive, see THIS post for many details. The summary is to plan to have used 150% of the actual miles from the previous charging point. This leaves you a lot of room to cover bad weather and high speeds. You will hopefully generally arrive with more miles than that; congratulations, you are ahead of schedule. Feels better than being behind schedule, eh? Plan for the worst case, but realize that on good days you can come out ahead. Maybe that extra time will make up for any problems that you can’t anticipate, like all chargers being in use when you arrive. (That has only happened to me once. I talked to the other owner for half an hour and then plugged in).
How long it takes to get the charge
The key determinant is what you are plugged in to. The chart HERE gives you nominal rates for each type of charger. As that post notes, your car has to be able to handle the power offered – i.e. you must have Supercharge hardware to use Superchargers, and you must have Twin Chargers to take advantage of 240V EVSEs with more than 40A.
The general idea behind the numbers in the chart is this: multiply volts*amps to get Watts of power provided by the charger. Then divide by your car’s rated (Watt*hour)/mile to get the miles of rated range that you will get per hour of charging. For example, at a 240V NEMA 14-50 campground outlet, with a 308Wh/mi Model S, you can expect a nominal maximum of 240V * 40A / 308Wh/mi = 31m/h. The number in the chart is actually 29mph because of inefficiencies in the charging process.
As an example, say you roll in to a campground with 75 miles of rated range left, and it is 100 miles to the next charger. As noted above you don’t want to leave until the car shows 175 miles of rated range. So you need to add 100 miles of range at this charger; at 29 mph that will take almost 3.5 hours. Perhaps even longer if any of the factors below come in to play. Yeah, that’s a long time; that’s why you want to use faster chargers whenever they are available! (My first trip used campgrounds, but I’ve always used at least HPCs since then).
There are many factors that can lower your charging rate below the maximum values in that chart. They include:
· The outlet could have lower voltage. This is most common at Level 2 EVSEs, which are 240V when you are lucky, but in practice often on commercial 208V legs. Plus other loads may cause the voltage to sag. Seeing 200V is not uncommon at L2 EVSEs. That will increase your charging time by 20%.
· It could be lower current. For example, Tesla’s HPWC is rated for 80A when installed on a 100A circuit. But any given installation could be on a smaller breaker, so the current may be well under 80A. There are some Roadster HPCs in Fairfield CA that only allow a 32A draw. What a disappointment; that will more than double the charging time.
· To protect the battery (when near full in Range Mode, or when it is hot outside) the car may ask for the amp level to be dialed down. You probably won’t notice this with 110V charging; and the effect is usually very small on 240V charging as well if you are charging in Standard mode. It is noticeable with a Supercharger; in fact charging from 20 – 80% may be faster than charging from 90 – 100%. Again, this is only a significant issue if you need a Range mode charge.
· If it’s hot or very cold, the car will divert power to manage the battery temperature. This matters most at 110V, where in extreme conditions you may find your car not being charged at all. On a Supercharger, this is unlikely to be a measurable drain. For 240V charging in extreme weather, this might increase your charge times by ~30% if you are on a slow 30A EVSE, but 10% is more likely on an 80A HPWC.
· If it’s really hot or cold and you are in the car with the HVAC on, power will be diverted to keeping you comfortable rather than charging the batteries. On 110V in extreme conditions you may actually LOSE charge. On a Supercharger you might start to notice increased charging times, but the delta should be less than 10%. For 240V charging in extreme weather, the effect of HVAC is probably (I am guessing rather than using real numbers here) twice as large as the effect of battery conditioning. So on a slow 30A EVSE in very extreme conditions, you and your battery may be very comfortable, but you might never get the charge you want. An 80A HWPC may take nearly twice as long to finish.
In addition to the possible drains on max-speed charging above, charging speed will also ramp down as the battery gets full. Exactly when it ramps down and how far it ramps down depends on a lot of things – type of charger, size of your pack, ambient temperature, pack temperature, etc. Here are some general thoughts based on the type of charging you are doing:
· 110V: yikes, I hope you’re not using this on a road trip. But 110V is slow enough that you won’t notice a slowdown near the end, so no need to consider this.
· 240V: The rampdown doesn’t happen until after you get a full Standard Mode charge of 240 miles. In most cases you will stop at that point anyway. But if you need it to ensure you have enough range to reach the next charger, you should figure the miles from 240 to 265 will take about twice as long as the earlier miles (although it varies depending on charger speed and conditions, and is not linear). Figure an hour or so to go from 240 to 265 miles even on an 80A HPWC.
· Supercharger: the rampdown starts pretty early, maybe even before the battery is half full. But the rampdown is very gradual (so there’s no obvious point at which to stop) and the rate is still very quick. Given the many advantages to having more juice in your pack, leaving early just to make the same charging some minutes faster at the next site is not generally your best strategy. But if you have another reason to leave (bored, others waiting to charge, etc) this gives you one more reason to leave once you have at least 150% of the miles needed to reach the next one.
The key points
· Road trips in an EV do take planning…but fortunately they are optional
· Plan charging stops no more than 177 miles apart
· Plan to have your range reduced by 150% of the actual miles while driving
· Charge until your car shows enough rated miles to cover 150% of the actual distance to the next charger, plus 25 miles
· However long you spend driving, plan on spending very roughly twice that much time charging if you are using a 30A EVSE or pulling 40A from a campground outlet. Plan on spending about the same amount of time charging as driving if you can use 70A HPCs or 80A HPWCs. Plan on spending about 1/3 as much time charging if you are using Superchargers.
Applying it to a real trip
In January 2013 we drove from Seattle to Death Valley and back. We spent a couple of days in Death Valley as well as a couple of days in the Bay area; those are ignored for our purposes here to focus on the travel days. We spent four days using Level 2 chargers, and 2 days using Superchargers. Temperatures ranged from 25 to 70 degrees on this trip. Charging was usually done with temperatures in the 40’s, which didn’t seem to have much effect on charging times.
The Level 2 240V chargers were all Roadster HPCs; 70A at up to 240V. After charging losses ~50mph is probably the fastest charging we’d really expect to see. And few of the chargers are at 240V; most are slightly under 208V which is 14% less so we’d expect more like 43mph. Of course it could be even worse if we sat in the car and ran HVAC, although we didn’t do that on this trip. There also could be some overhead to heat or cool the batteries; on this trip it didn’t seem to get warm enough to have to cool them. It was around freezing several times, but from looking at the actual charging rate it doesn’t appear much if anything was used to heat the batteries – they were probably warm enough to accept an L2 charge (which isn’t very intense on a battery this large) from driving and then from overhead heat released during charging.
As you can see from the chart below, we actually saw 50mph at the 240V nominal charger (47 the second time, but that included a Range Mode charge that slowed down the overall rate), and 41-44 at the slightly saggy 208V nominal chargers, so the numbers were right in line with expectations.
As for the Superchargers, there is good news and bad news. The good news is that, yes, they are WAY faster than 70A Roadster HPCs. Probably at least 3 times as fast. The bad news is that we did not get anywhere near 300 miles per hour. Of course we didn’t really expect that much, but our actual rates were between 108 and 167mph, with an average of 139. I was expecting to see 200mph on some of them, and at least 150mph on all of them. I know there have been some threads on Supercharger charging rates, so I’ll have to examine those. I was running 1.15.14 at the time, so it’s possible that contributed. It was also pretty cold for most of the charging we did, though I wouldn’t think that would hurt.
Day 1 on Level 2
Day 2 on Level 2
Day 3 on Level 2
Day 4 on Level 2
Day 1 on Superchargers
Day 2 on Superchargers
· how often to stop
· where to stop
· how much charge to replenish
· how long charging will take
We will cover those issues one by one below; but before we get in to that, we should have:
A note for EV newcomers
Driving electric has many advantages. Smoother, more responsive, quieter, lower center of gravity, less maintenance, cheaper to own than comparable gas cars, cleaner, use US fuel, and all that. However, fully-electric vehicles do have one disadvantage: road trips take longer. That is because charging is slower than refueling - which doesn’t matter for everyday use where you charge overnight in your garage, but can be a drag on a long drive. Fear of this situation is why many people are sticking with gas cars, and missing out on all of the electric advantages.
However, a disadvantage is not really a disadvantage if you never encounter it – and all-electric road trips are REALLY easy to avoid. First, you can always buy a plug-in hybrid (PHEV), which will electrify most of your driving but still has a gas engine so road trips are unchanged. It doesn’t get any simpler than that.
You may prefer an an all-electric car (less maintenance, more range, better packaging and less cost than a comparable PHEV), and that's fine because there are still many ways to avoid having to plan an electric road trip. You could take a second family car, rent or swap a car, fly/bus/train, etc. Buying an electric car does not require you to sign a pledge saying you will never use any other form of transport. Not only do many plug-in owners never take a road trip in an all-electric vehicle, but many plug-in owners never charge their cars anywhere other than in their own garage.
Even though you don’t have to take an all-electric road trip, you may find that you want to. Gas cars are noisy, they vibrate and jerk as you accelerate, the accelerator is not nearly as responsive, gas is expensive and dirty while the solar-powered Superchargers are free…this post is optional reading for those owners that choose to take a long electric trip.
[Pic: my Seattle-based Roadster in San Diego, April 2010]
[Pic: my Model S in Death Valley, January 2013]
How often to stop
The key rule-of-thumb is to never plan to drive farther than 2/3 of your EPA range without charging (although you may alter that plan slightly as you are taking the trip depending on conditions). That’s 177 miles in an 85kWh, 139 miles in a 60kWh, and 95 miles in a 40kWh. For simplicity I will assume an 85kWh car in this post.
There are many details behind the 2/3 number HERE. With that information you can make some adjustments for a specific trip; but the simple rule of thumb that should cover the vast majority of cases is to not plan your charging stops any more than 177 miles apart. While you may go much farther than 177 miles if you drive slowly on a nice day (300 miles really IS possible), surprise bad weather - including headwinds on an otherwise nice day - could bring your range way down even if you drive conservatively. And when weather conditions are good, the Model S makes it hard to drive slow – but faster driving uses a lot more energy.
Planning more frequent stops is more work, so most people grumble about limiting trip legs to 177 miles. They grumble even more when I point out even that may sometimes be too far. What if the charger is broken or blocked? You should always leave a buffer for that. Shorter trip legs with more frequent charging:
· keep you from worrying if you will reach the next charger or not
· keep you from having to slow down or turn off the climate control
· give you a lot more options if you run in to a problem with the next charger
· keep your battery closer to the middle where it is most comfortable
· give you more breaks from driving (177 miles is 2 - 3 hours; a break is a good idea anyway)
· help keep any single break from getting overly long
You can always skip (or more likely, cut short) a planned charging stop if conditions are good and you don’t need it. But plan for it anyway. I tried stretching my range on my first long trip, and had several problems. I learned my lesson and don’t do that anymore; I have since taken 5 long trips (1,600 to 3,000 miles each) with shorter legs and have had no issues – the trips are much more enjoyable that way!
Where to stop
Inside your 177-mile range, the primary thing that determines where you make a charge stop will be is the availability of the fastest charger you can access. If you need a reminder of what types of places you can plug in to, what you need to use them and how fast they are, there is a list HERE.
If you have more than one charging site to choose from, you should take in to consideration what you can do at each location while charging. There is no point to just stand around and wait for your car to charge, so look for things you’d like to do anyway – visit friends, go to a museum, watch a movie, eat, spend the night, read, get some exercise, check email, etc. Charging time is not wasted time if you are doing something you want or need to do. Is the charging location protected from the weather? Are there restrooms, internet access, walking paths or parks nearby? Are there other chargers nearby in case there is a problem with the one you plan to use?
If you happen to be on the US West coast, HERE is a map that shows you Tesla Superchargers, high-amp J1772 stations, and Roadster HPCs as well as a few “strategic” 14-50 outlets and low-amp EVSEs. You can also use EVSE-finder sites like the following (this is not an exhaustive list; just some sites that I happen to use. No one site has every option):
· recargo.com
· carstations.com
· chargepoint.net – the first charging network to include chargers outside its network. Includes station status for Chargepoint stations
· plugshare.com – originally a network of owner outlets, now includes public outlets too - so perhaps the most comprehensive overall
Plus you can look at any number of campground directories that list campgrounds with 50-amp electrical service. (Be sure to ask for “50 amp”, not “240 volt” or “NEMA 14-50” which often cause confusion).
How much charge to replenish
The simplest method is to reverse the 2/3 leg-length mantra, and to say that you will charge until you have at least 150% of the miles necessary to reach the next charging point. At least 150% - you really should add an extra ~25 miles in case there is a problem at the next charger and you have to drive to charge somewhere else. For example, if it’s 100 miles to the next charger, you should not leave your current charging station until your car says you have 175 miles of rated range. That may seem like a lot, but just think how nice it will be to take that drive with no worries about getting there! Besides, unless it’s your last charge of the day, any leftover charge will save you time at the next stop anyway.
If charging conditions are ideal, you may want to stay even longer as having more charge is always better. Well, always better up to the full 240 miles in Standard Mode, anyway. Tesla does not recommend frequent Range Mode charging and charging is slower in Range Mode, so only wait for that if you need it to reach the next charger – or if you are hanging around anyway (i.e. spending the night) and want to use the idle time charging to save time on your next charge. For example if you are at the fastest charger on your trip, and nobody else is waiting for it, and you have things to do there…well, stick around and charge until 240 miles. But if you get bored, or the next charger is faster, or somebody is waiting for this one, you might want to leave as soon as you get to 150% of the miles needed to make the next charger. Perhaps a little sooner if the weather and road conditions are favorable and you don’t plan on going fast; but you should have some road trip experience under your belt before you try that.
The above describes when you have enough miles to leave. To make an estimate of how many miles of range you will have when you arrive, see THIS post for many details. The summary is to plan to have used 150% of the actual miles from the previous charging point. This leaves you a lot of room to cover bad weather and high speeds. You will hopefully generally arrive with more miles than that; congratulations, you are ahead of schedule. Feels better than being behind schedule, eh? Plan for the worst case, but realize that on good days you can come out ahead. Maybe that extra time will make up for any problems that you can’t anticipate, like all chargers being in use when you arrive. (That has only happened to me once. I talked to the other owner for half an hour and then plugged in).
How long it takes to get the charge
The key determinant is what you are plugged in to. The chart HERE gives you nominal rates for each type of charger. As that post notes, your car has to be able to handle the power offered – i.e. you must have Supercharge hardware to use Superchargers, and you must have Twin Chargers to take advantage of 240V EVSEs with more than 40A.
The general idea behind the numbers in the chart is this: multiply volts*amps to get Watts of power provided by the charger. Then divide by your car’s rated (Watt*hour)/mile to get the miles of rated range that you will get per hour of charging. For example, at a 240V NEMA 14-50 campground outlet, with a 308Wh/mi Model S, you can expect a nominal maximum of 240V * 40A / 308Wh/mi = 31m/h. The number in the chart is actually 29mph because of inefficiencies in the charging process.
As an example, say you roll in to a campground with 75 miles of rated range left, and it is 100 miles to the next charger. As noted above you don’t want to leave until the car shows 175 miles of rated range. So you need to add 100 miles of range at this charger; at 29 mph that will take almost 3.5 hours. Perhaps even longer if any of the factors below come in to play. Yeah, that’s a long time; that’s why you want to use faster chargers whenever they are available! (My first trip used campgrounds, but I’ve always used at least HPCs since then).
There are many factors that can lower your charging rate below the maximum values in that chart. They include:
· The outlet could have lower voltage. This is most common at Level 2 EVSEs, which are 240V when you are lucky, but in practice often on commercial 208V legs. Plus other loads may cause the voltage to sag. Seeing 200V is not uncommon at L2 EVSEs. That will increase your charging time by 20%.
· It could be lower current. For example, Tesla’s HPWC is rated for 80A when installed on a 100A circuit. But any given installation could be on a smaller breaker, so the current may be well under 80A. There are some Roadster HPCs in Fairfield CA that only allow a 32A draw. What a disappointment; that will more than double the charging time.
· To protect the battery (when near full in Range Mode, or when it is hot outside) the car may ask for the amp level to be dialed down. You probably won’t notice this with 110V charging; and the effect is usually very small on 240V charging as well if you are charging in Standard mode. It is noticeable with a Supercharger; in fact charging from 20 – 80% may be faster than charging from 90 – 100%. Again, this is only a significant issue if you need a Range mode charge.
· If it’s hot or very cold, the car will divert power to manage the battery temperature. This matters most at 110V, where in extreme conditions you may find your car not being charged at all. On a Supercharger, this is unlikely to be a measurable drain. For 240V charging in extreme weather, this might increase your charge times by ~30% if you are on a slow 30A EVSE, but 10% is more likely on an 80A HPWC.
· If it’s really hot or cold and you are in the car with the HVAC on, power will be diverted to keeping you comfortable rather than charging the batteries. On 110V in extreme conditions you may actually LOSE charge. On a Supercharger you might start to notice increased charging times, but the delta should be less than 10%. For 240V charging in extreme weather, the effect of HVAC is probably (I am guessing rather than using real numbers here) twice as large as the effect of battery conditioning. So on a slow 30A EVSE in very extreme conditions, you and your battery may be very comfortable, but you might never get the charge you want. An 80A HWPC may take nearly twice as long to finish.
In addition to the possible drains on max-speed charging above, charging speed will also ramp down as the battery gets full. Exactly when it ramps down and how far it ramps down depends on a lot of things – type of charger, size of your pack, ambient temperature, pack temperature, etc. Here are some general thoughts based on the type of charging you are doing:
· 110V: yikes, I hope you’re not using this on a road trip. But 110V is slow enough that you won’t notice a slowdown near the end, so no need to consider this.
· 240V: The rampdown doesn’t happen until after you get a full Standard Mode charge of 240 miles. In most cases you will stop at that point anyway. But if you need it to ensure you have enough range to reach the next charger, you should figure the miles from 240 to 265 will take about twice as long as the earlier miles (although it varies depending on charger speed and conditions, and is not linear). Figure an hour or so to go from 240 to 265 miles even on an 80A HPWC.
· Supercharger: the rampdown starts pretty early, maybe even before the battery is half full. But the rampdown is very gradual (so there’s no obvious point at which to stop) and the rate is still very quick. Given the many advantages to having more juice in your pack, leaving early just to make the same charging some minutes faster at the next site is not generally your best strategy. But if you have another reason to leave (bored, others waiting to charge, etc) this gives you one more reason to leave once you have at least 150% of the miles needed to reach the next one.
The key points
· Road trips in an EV do take planning…but fortunately they are optional
· Plan charging stops no more than 177 miles apart
· Plan to have your range reduced by 150% of the actual miles while driving
· Charge until your car shows enough rated miles to cover 150% of the actual distance to the next charger, plus 25 miles
· However long you spend driving, plan on spending very roughly twice that much time charging if you are using a 30A EVSE or pulling 40A from a campground outlet. Plan on spending about the same amount of time charging as driving if you can use 70A HPCs or 80A HPWCs. Plan on spending about 1/3 as much time charging if you are using Superchargers.
Applying it to a real trip
In January 2013 we drove from Seattle to Death Valley and back. We spent a couple of days in Death Valley as well as a couple of days in the Bay area; those are ignored for our purposes here to focus on the travel days. We spent four days using Level 2 chargers, and 2 days using Superchargers. Temperatures ranged from 25 to 70 degrees on this trip. Charging was usually done with temperatures in the 40’s, which didn’t seem to have much effect on charging times.
The Level 2 240V chargers were all Roadster HPCs; 70A at up to 240V. After charging losses ~50mph is probably the fastest charging we’d really expect to see. And few of the chargers are at 240V; most are slightly under 208V which is 14% less so we’d expect more like 43mph. Of course it could be even worse if we sat in the car and ran HVAC, although we didn’t do that on this trip. There also could be some overhead to heat or cool the batteries; on this trip it didn’t seem to get warm enough to have to cool them. It was around freezing several times, but from looking at the actual charging rate it doesn’t appear much if anything was used to heat the batteries – they were probably warm enough to accept an L2 charge (which isn’t very intense on a battery this large) from driving and then from overhead heat released during charging.
As you can see from the chart below, we actually saw 50mph at the 240V nominal charger (47 the second time, but that included a Range Mode charge that slowed down the overall rate), and 41-44 at the slightly saggy 208V nominal chargers, so the numbers were right in line with expectations.
As for the Superchargers, there is good news and bad news. The good news is that, yes, they are WAY faster than 70A Roadster HPCs. Probably at least 3 times as fast. The bad news is that we did not get anywhere near 300 miles per hour. Of course we didn’t really expect that much, but our actual rates were between 108 and 167mph, with an average of 139. I was expecting to see 200mph on some of them, and at least 150mph on all of them. I know there have been some threads on Supercharger charging rates, so I’ll have to examine those. I was running 1.15.14 at the time, so it’s possible that contributed. It was also pretty cold for most of the charging we did, though I wouldn’t think that would hurt.
Day 1 on Level 2
Where | Distance driven | Rated miles used | Rated miles at start | Rated miles at end | Charging goal: 150%+25 | Time consumed | Rated miles gained per hour of charge | Charging equipment | Notes |
Driving | 93 miles | 129 (139%) | 268 | 1:42 | |||||
Charging in Centralia WA | 139 | 185 | 175 | 1:05 | 42 | 207V 70A Roadster HPC | |||
Driving | 100 miles | 137 (137%) | 1:43 | ||||||
Charging at Tesla Portland | 48 | 234 | 183 | 4:15 | 44 | 207V 70A Roadster HPC | Lots to do here, so we stayed longer than needed | ||
Driving | 105 miles | 130 (123%) | 1:45 | ||||||
Charging in Eugene OR | 104 | 159? | 162 | 1:20 | 41 | 202V 70A Roadster HPC | |||
Driving | 93 miles | 126 (138%) | 33 | 1:30 | |||||
Day's totals | 389 miles | 13:20 (6:40 charging) |
Day 2 on Level 2
Where | Distance driven | Rated miles used | Rated miles at start | Rated miles at end | Charging goal: 150% + 25 | Time consumed | Rated miles gained per hour of charge | Charging equipment | Notes |
Driving | 124 miles | 180 (145%) | 265 | 2:23 | |||||
Charging in Yreka CA | 85 | 240 | 258 | 3:33 | 44 | 206V 70A Roadster HPC | Left before getting 150% because of elevation loss ahead | ||
Driving | 155 miles | 161 (104%) | 2:28 | ||||||
Charging in Orland CA | 79 | 188 | 166 | 2:11 | 50 | 236V 70A Roadster HPC | Meal service was slow so we stayed a little longer than we had to | ||
Driving | 94 miles | 115 (122%) | 73 | 1:28 | |||||
Day's totals | 373 miles | 12:03 (5:44 charging) |
Day 3 on Level 2
Where | Distance driven | Rated miles used | Rated miles at start | Rated miles at end | Charging goal: 150% + 25 | Time consumed | Rated miles gained per hour of charge | Charging equipment | Notes |
Driving | 94 miles | 126 (134%) | 264 | 1:29 | |||||
Charging in Orland CA | 138 | 267 | 258 | 2:44 | 47 | 236V 70A Roadster HPC | Range mode charge slowed down rate | ||
Driving | 155 miles | 200 (129%) | 2:17 | ||||||
Charging in Yreka CA | 67 | 215 | 211 | 3:52 (not charging for ~20 mins) | ~42 | 207V 70A Roadster HPC | Gave owner a ride; used ~4 miles of range | ||
Driving | 124 miles | 143 (115%) | 72 | 1:55 | |||||
Day's totals | 373 miles | 12:23 (6:16 charging) |
Day 4 on Level 2
Where | Distance driven | Rated miles used | Rated miles at start | Rated miles at end | Charging goal: 150%+25 | Time consumed | Rated miles gained per hour of charge | Charging equipment | Notes |
Driving | 91 miles | 116 (127%) | 260 | 1:29 | |||||
Charging in Eugene OR | 144 | 234 | 183 | 2:03 | 44 | 202V 70A Roadster HPC | Don't recall why we stayed so long; multiple chargers in Portland | ||
Driving | 105 miles | 124 (118%) | 1:40 | ||||||
Charging at Tesla Portland | 110 | 182 | 175 | 1:41 | 43 | 207V 70A Roadster HPC | |||
Driving | 100 miles | 128 (128%) | 1:38 | ||||||
Charging in Centralia WA | 54 | 141 | 165 | 2:00 | 43 | 207V 70A Roadster HPC | Left early because we were comfortable with route and weather, and had backup | ||
Driving | 93 miles | 113 (122%) | 28 | 1:18 | |||||
Day's totals | 389 miles | 11:59 (6:44 charging) |
Day 1 on Superchargers
Where | Distance driven | Rated miles used | Rated miles at start | Rated miles at end | Charging goal: 150% + 25 | Time consumed | Rated miles gained per hour of charging | Charging equipment | Notes |
Driving | 46 miles | 58 (126%) | 173 | 0:49 | |||||
Charging in Gilroy CA | 115 | 185 | 192 | 0:39 | 108 | Supercharger | Left early: trying lower SOC | ||
Driving | 111 miles | 142 (128%) | 1:49 | ||||||
Charging at Harris Ranch | 43 | 185 | 216 | 0:51 | 167 | Supercharger | Left early: good weather, lower SOC | ||
Driving | 127 miles | 152 (120%) | 1:40 | ||||||
Charging in Tejon Ranch | 33 | 213 | 249 | 1:10 | 154 | Supercharger | Warm and trying low SOC again | ||
Driving | 149 miles | 188 (126%) | 25 | 2:26 | |||||
Day's totals | 433 miles | 9:24 (2:40 charging) |
Day 2 on Superchargers
Where | Distance driven | Rated miles used | Rated miles at start | Rated miles at end | Charging goal: 150% + 25 | Time consumed | Rated miles gained per hour of charging | Charging equipment | Notes |
Driving | 70 miles | 72 (103%) | 146 | 1:14 | Adjusted start miles for cold soak | ||||
Charging in Tejon Ranch CA | 74 | 240 | 199 | 1:17 | 130 | Supercharger | |||
Driving | 116 miles | 150 (129%) | 1:48 | ||||||
Charging at Harris Ranch | 90 | 217 | 193 | 0:54 | 141 | Supercharger | |||
Driving | 112 miles | 138 (123%) | 2:04 | ||||||
Charging in Gilroy CA | 79 | 231 | 222 | 1:07 | 136 | Supercharger | |||
Driving | 131 miles | 149 (114%) | 82 | 2:00 | |||||
Day's totals | 429 miles | 10:24 (3:18 charging) |
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