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Hi,
For most EV driving, a fast-charger is not needed; but it's nice to have the
capability. Mostly, in practice, Tesla owners use the 120v convenience charger,
not the 70A 240 outlet.
The one place fast charging is helpful is on long trips; on city voyages, mostly
the car sits around (unless you're a speedy messenger?) and can charge while you
spend time at the place you spent energy to visit. The average car sits unused
23 hours per day.
You can calculate exactly how FAST you can travel in an EV on long distance
trips by how fast the charger works.
Let's say you can charge at 10 kW; that's 10 kWh per hour. 10 kWh takes you up
to 60 miles in an EV1 (30 to 40 miles in a RAV4-EV, and 50 miles in a Tesla or
Mini-E). Depending on the distance, that's 1 hour, .67 hour, or .84 hour of
driving; add that to the charge time, and you get total mph over distance.
So in an EV1 with optional fast-charging add-on, if you charge for one hour at
10 kW, you can drive 60 miles on the 10 kWh you reaped; over both charging and
driving hours, that's an average speed of 30 mph.
To do this calculation, the number of hours you spend at each charger is
irrelevant; it could be 60, or 120, or 180 miles between chargers, depending on
the kWh capacity of the EV.
There's an anomaly created by how many kWh the EV holds, because you can stop
recharging it when you're in range of your destination; thus devolving into the
trival case of driving inside your range limit.
Hence, there's a table, idea due to Will Korthof, that can show the effects of
charging speed on long-distance travel mph in an EV1:
EV1 CHARGER.....ONE-HOUR.....60mphDIST..TIME...TOT. MPH
5 kW.............5 kWh...x6....30m......0.5hr...30/1.5===20 MPH
10kW............10 kWh...x6....60m......1.0hr...60/2=====30 MPH
12kW (50A240v)..12 kWh...x6....72m......1.2hr...72/2.2===33 MPH
24kW (100A).....24 kWh...x6...144m......2.2hr..144/3.2===45 MPH
For a RAV4-EV (assuming 3 miles per kWh):
RAV4-EV CHG.....ONE-HOUR......60mphDIST..TIME...TOT. MPH
5 kW.............5 kWh...x3....15m......0.25hr...15/1.25==12 MPH
12kW (50A240v)..12 kWh...x3....36m......0.6 hr...36/1.6===23 MPH
24kW (100A).....24 kWh...x3....72m......1.2 hr...72/2.2===33 MPH
I like the visual appeal of tables; but here's the formula:
For each one-hour of charging,
..K=kW of charger, can be add-on
..M=miles per kWh depending on car
..D=Distance traveled on one hour charge
..T0=Time of charging (assume 1 hour)
..T1=Time of travel at assumed speed (60 mph)
TMPH=resultant miles per hour, including charge time
TMPH=(K*M)/(T0+[K*M/T1])
For the TESLA, assming K=18, M=5:
TMPH=90/(1+[90/60]) or 90/2.5, 36 mph.
Assuming a TESLA with a really fast charger, say K=30:
TMPH=150/(1+[150/60]) or 150/3.5, 43 mph.
Thus, driving a RAV4-EV to SF can be a lengthy process (Will took me on one such
trip in our RAV4-EV "nogaso" a few years ago, using the Manzanita 12 kW
conductive charger). Conversely, you can make it to SF in an EV1, with 6 miles
per kWh, in less than 24 hours (Lisa and I did so in a rented EV1, using the
last 26 kWh for the last leg).
A lot depends on the volts and amps in the charger; COSTCO sites are only 208
volts, and the amps are 30, so it's 6 kW, pathetic; RV parks with 50A and 240
volts are the best commonly available (12 kW).
So when Bill and another engineer drove an EV1 to Toronto, and then to NY, they
figured out how to goose the on-board to 10kW; it was still pretty lengthy, even
with the 6 miles per kWh.
Now let's look at the TESLA, which can charge at 70 A 240V, or almost 18 kWh,
and which gets 5 miles per kWh:
TESLA..........ONE-HOUR CHARGE.....DIST@.... MPH
18kW...........18 kWh..............90 miles.......90/2.5==36 MPH
So you can make it to SF, 400 miles, in 11 hours, formally.
Of course, you CAN arrive NOT FULL; so if you arrive empty, and if the TESLA
holds 53 kWh, you cut the trip by at least 2 hours, since you don't count the
time you charge at your destination. So it's only 9 hours, or perhaps less if
you arrive emptier or don't go as far into SF.
Here's the Golden State Freeway "ELECTRIC CORRIDOR" to SF, assuming maximum
charge time at the highest kW, and assuming an EV that gets 5 miles per kWh:
LOST ANGELES
--48 Miles
--.8 hours driving
CASTAIC RV PARK 14/50 outlet (12kw)
(used 10 kWh, takes .8 hours to recharge to 100%)
(cum. time = 1.6 hours)
--103 Miles (cum. 151 miles)
--1.5 hours driving
LOST HILLS RV PARK 14/50 outlet (12kW)
(used 21 kWh, takes 1.9 hours to recharge to 100%)
(cum. time = 1.6+1.5+1.9 = 5.0 hours)
--47 Miles (cum. 198 miles)
--.8 hours driving
JAYNE RV PARK 14/50 outlet (12kW)
(used 9 kWh, takes .8 hours to recharge to 100%)
(cum. time = 5.0+0.8+.08 = 6.6 hours)
--82 Miles (cum. 280 miles)
--1.2 hours driving
LOS BANOS RV PARK 14/50 outlet (12kW)
(used 16 kWh, takes 1.25 hours to recharge to 100%)
(cum. time = 6.6+1.2+1.2= 9 hours)
--66 Miles (cum. 346 miles)
--1.1 hours driving
SAN JOSE COSTCO (Avcon 6 kW)
(used 13 kWh, takes 1 hour to recoup 6 kWh; leaving partly empty)
(cum. time = 9+1.1+1= 11.1 hours)
--67 Miles (cum. 413 miles)
--1.1 hours driving
SAN FRANCISCO
(used 13 kWh; arriving partly filled)
(cum. time = 11.1+1.1 = 12.2 hours)
TOTAL KWH USED: 82 kWh, the energy equivalent of 3.3 gallons of gasoline.
COST @ 10 CENTS PER KWH: $8.20
COST PER KWH FOR THOSE KWH FROM OWN SOLAR: $0.00
COST OF DRIVING AVERAGE CAR IN GAS (20 GAL.) ALONE: $66+
COST OF OIL WARS TO SUPPORT BIG OIL ($4/GAL.): $120+
MONEY TO BIG OIL WHEN DRIVING EV: ZERO
MONEY TO BIG OIL WHEN DRIVING IC (20 GAL): $40.00
MONEY SUPPLIED BY TAXPAYER TO SUPPORT OIL WARS: $120+
COST OF AFTERCARE, HEALTH, SUBSIDIES, EST: $60+
Hm. Maybe that's what they hate about EVs.
The Electric Corridor assumes, for an EV that gets 5 miles per kWh, that it
holds at least 21 accessible kWh; that's to get over the 4144 ft. Tejon Pass,
103 miles from Castaic to Lost Hills. Once with the HondaEV, coming from
Bakersfield, we made it all the way to LADWP, over Tejon Pass arriving with 23%
left; we could have made it all the way to Seal Beach from Bakersfield.
Also, the more the EV holds in kWh, the shorter the charge time for the trip,
because you can hold off charging on the last leg until you get to a fast
charger, and arrive emptier (using more of the charge you started out with, also
not travel time).
This Electric Corridor has been existence long before Shcwarzenegger's pipe
dreams of 'hydrogen hypeway' crashed to the gutter.
Doug {Korthof}
