Mr. Green Car: Tesla S sedan — a test drive, part four: charging
Editor’s note: The following is the fourth in a four-part series. Part one appeared in the Dec. 3-9, 2014, issue, part two appeared in the Dec. 24-30, 2014, issue, and part three appeared in the Jan. 7-13, 2015, issue.
By Allen Penticoff
Let’s say you have a Tesla Model S sedan. What can you do with it? Is it as practical as driving a gasoline-powered car?
If you owned one in Rockford, and had frequent need to travel to Springfield, the state capital, you could make the round trip essentially free. With the battery topped off, even with the 60-Kwh model, you can roll the 198 miles to Springfield within the 208 EPA mile range.
Since there is a new Tesla Supercharger in Springfield, you can top off the battery in something more than 30 minutes before heading home (see details below). Upon returning to Rockford, you could swing by the Tesla Supercharger at CherryVale Mall and top off your batteries once again — for free. Or just go home and plug in your home 240-volt charger that will cost you about $7 for electricity (3.1 mi./Kw). A gasoline-powered car, getting 25 mpg on the highway, would cost you $32 at today’s extraordinarily low gas prices.
I’ve found in a year of driving a Chevy Volt around that with only 28-53 miles of range, depending on ambient temperature — that we can do all of our daily running around on electricity — and that’s with its puny stock 120-volt charger. From April 1 to the end of November, we drove it 6,005 miles and filled the tank once at the end of that time — 6.8 gallons — most of which was burned on individual trips to Freeport and back. What this indicates is that with the Tesla’s far larger 60-Kwh or 85-Kwh battery pack versus the Volt’s 17-Kwh, you are unlikely to run out of electricity and won’t need to go looking for a recharge around town. Tesla owners can also find Tesla Superchargers along the interstates to drive across the country for free.
I should explain that when I refer to the “battery” in a Tesla Model S, what we’re really talking about for the 85-Kwh “battery” is 7,104 modified Panasonic laptop batteries, each coated with a material that will suppress a thermal runway. Further, the whole “battery” has a liquid cooling system. Other EV builders are using “large format” batteries in their battery assemblies. It should come as no surprise that Panasonic is an investor in Tesla Motors. The warranty for the 60 Kwh battery is eight years, 125,000 miles, while the 85-Kwh battery is eight years, unlimited miles. I won’t say what replacement cost will be, as the price of the laptop batteries used will continue to drop as Tesla ramps up production in their battery giga-factory. However, you can purchase a battery replacement option with a new Tesla: $10,000 (60 Kwh) or $12,000 (85 Kwh).
Tesla claims the range of a Tesla Model S with the 85-Kwh battery is 306 miles (at 55 mph). This reflects the “old” way of determining range. However, the EPA is imposing a 10 percent decrease in advertisable range on EVs that have user adjustable charge rates. Right now, I have no idea why. So, this same car has an EPA range of 265 miles. The P85D model has an EPA (pending) range of 253 miles. Also, Tesla advises owners to expect 3 percent less range with 21-inch wheels. For now, I would consider the EPA range as very realistic, and let Tesla’s claims of higher mileage serve as reserve capacity. In ordinary daily use, it will not matter. As with any EV, ambient temperature will have a significant effect on range. This is one of the things about Tesla’s big battery capacity: even with a 50 percent reduction in range during very cold weather, you will still have plenty of power for daily needs.
In fact, if you don’t intend to drive your Tesla Model S out of town much, or will drive something else when you do, then you might consider saving the $10,000 additional cost of the bigger 85-Kwh battery pack and go with the 60-Kwh battery. The 60-Kwh cars do not come with the ability to use a Tesla Supercharger, but this can be added as a $2,000 option. The 85-Kwh cars come with this standard. The Tesla Superchargers use 480-volt DC current to fire-hose electricity into the batteries at locations handy to interstate highways and nearby places to eat or kill time (i.e., shopping malls). Nonetheless, a 60-Kwh car without supercharging can still fill up at home in a few hours.
Two options are offered for charging the batteries of the Tesla Model S at home. The standard single 40-amp, 240-volt charger or the $1,500 Dual 240-volt, 80-amp charger option. With the dual charger option, you will still only plug in one cord to a charger — but the onboard chargers are doubled to handle the higher current. Your house wiring will probably need upgrading to handle 240 volts at 80 amps. You could weld some pretty thick metal with that kind of current.
The charge port is in the left rear taillight assembly. A small door pops open, and the Tesla charge cord is plugged in. It is much smaller than those found on the Volt or Leaf, so an adapter is included with each car so one can charge at public charging locations with 120-volt or 240-volt chargers up to 80 amps. 120-volt charging is not recommended, but is possible should there be a need — it will take four times longer to charge.
The location of the charge point is one of the few complaints I have about the Telsa Model S. If the charger is ahead of you, as in most public charging or Superchargers — it will require that you drag a heavy electric cable from the charger back to the port on the left side, unless you back up to the charger. The cord will possibly be in the way for access to the left side of the car — and it most certainly will be dirty when you go to put it away after charging. Ladies might want to have a pair of gardening gloves for this chore. At home, you can locate your charge cord to be near the left rear of the car — where it will be out of the way and a short stretch to plug it in. At home, you probably won’t have to touch the cord. With my Volt, where the port is in front of the driver’s door, we have the charge cord set up to where it is easy to plug in without touching the cord or it being in the way at all. Port and charger location is something EV owners must take into consideration, both at home and with public charging.
Tesla’s website says that for a typical 40-mile usage, electricity will cost $1.58 at 12 cents per Kwh (national average) and take one hour and 21 minutes to charge at 240 volts with the single charger. The single 240-volt charger adds 29 miles of charge per hour, while the dual charger adds 58 miles of range per hour. The supercharger can add 170 miles of range in 30 minutes. Whether with the 240-volt charger, or the supercharger, the last few miles of charge will take considerably longer than the first miles because of the way the charger tapers off at the end when nearing full to avoid a battery damaging overcharge. In locations where you can get a better rate on your electricity at night, the charger can be programmed to turn on during the wee hours and still be full before commute time arrives. This feature is found on most factory made EVs. Also, there is a smartphone app that will show the state of charge and time to complete charge. You can also remotely turn on the air conditioning or heater with the smartphone app (again, this is common to most new EVs).
While I won’t go into great detail, since I’ve written about this topic previously — regenerative (regen) braking adds power back into the batteries every time you lift your foot off the accelerator. The Tesla Model S has full-time regenerative braking (as opposed to the Volt’s two settings with light regen and heavy regen). It is very pronounced and powerful, negating much of the need for touching the brakes except to make a complete stop. Regenerative braking adds significantly to your daily range when driving in city traffic. It has far less effect in highway driving, where 1 mile of driving will use 1 mile of range. The Tesla should be similar to my Volt — I recently left the house with 17 miles of range indicated. I made a 21-mile round trip and still had 3 miles of range showing when I parked in our garage. Slower speeds are more efficient as well. One Tesla Model S was driven more than 400 miles on one charge — but at a slow 30 to 35 mph.
While the Tesla Model S range could allow you to go for days without charging, lithium-ion batteries are happiest when kept fully charged. Deep discharges are not necessary for battery health, nor are they harmful. The best thing to do is to plug in the charger every time you park in the garage, whether you need it or not. It soon becomes an easy habit.
This concludes the Tesla Model S review, although I’m far from done with things to report about on Tesla-related news. At some time in the future, after I take a break from them, I will report on a Chicago-based company that uses the Tesla Model S as limousines.
From the Jan. 21-27, 2015, issue