Range Anxiety never goes away completely

The longer you drive your electric car the more you grow accustomed to how much energy it will consume along the routes you regularly drive.  The occasional new route is usually no sweat because you already know your safe driving radius from your home.  I know I can generally count on driving 4 miles per tick (out of 16) on the charge-level gauge, with each tick representing about 1KWh of charge.  So, I can safely drive about 60 miles without much worry and still have a margin of about 4 miles remaining.  My drive to work regularly uses up nine ticks, leaving me with six or so to run errands near home after work.  Most places I’ll visit are within 5 miles of home, so this works out well.  The problem comes when I start traveling unknown routes that extend to the range of my safe-driving radius, especially when a significant elevation change is involved.

The case-in-point happened last Mother’s Day (actually, the day before – to avoid the crowds).  My siblings decided to treat mom to a picnic at one of the nearby wineries in the Saratoga foothills.  Ordinarily, the trip from my house to the winery is about 16 miles, with the final 3 miles involving a significant climb in elevation.  32 miles round-trip is easy to do.  But, it was my turn to bring along mom, so I had to drive first to her place (14 freeway miles) and then to the winery (10 miles), for a total distance of 48 miles round-trip.  But, that morning I had to run an errand and used up 9 miles of charge already, making the total trip for one charge about 57 miles.  Factoring in the uphill climb was starting to make me nervous about completing the trip.  Fortunately, I had surface streets as backup options for the return trip home.

The trip went better than I had expected, thanks in part to two factors.  First, my morning errand was done entirely on city streets, which uses about 20% less charge to drive the same distance.  The second factor was more significant.  I keep thinking like I did in my gasoline powered car …  If I started my trip with 14 ticks on the gauge,  I would need 7 remaining by the time I reach my destination or I might not make it home.  As I was about a mile from the winery, the seventh tick cleared and I knew I would only narrowly make it home if I didn’t plan my driving carefully.  But, I wouldn’t have to worry about that until after the picnic at the winery.  Then, on the way home, the second factor kicked in.  Driving three miles downhill give me back one tick on the charge gauge, meaning that I had an extra four miles I could drive, and I used nothing for those three miles – for a total of seven miles.  (I’m telling you, it’s a mind game driving the hills in an electric car.)  The end result is that I had two ticks remaining on the charge gauge when I pulled into my driveway, and I was even able to run to the local store and back for dinner supplies.

A busy day ahead

It all started off easy enough…  I was invited to a party at my younger sister’s place on the east side of town.  Then, my mom called and told me that my older sister would be arriving the same afternoon and asked if I could give her a ride to mom’s place on the west side of town.  Then my older sister called and wanted to join me at our sister’s party before heading to mom’s.  With a reliable 60+ mile range, I was starting to worry about whether I could drive that far.  I tried estimating energy use in my head by counting the charge-level ticks it usually takes me to drive each stretch and came up with too many unknowns (and not enough ticks leftover for comfort).  So, I let the real engineer inside me solve the problem.  That, and a little help from Google Maps.

So, I needed to bring supplies (ie: wine) to the party on the east-side, wait for a phone call for a trip to the airport (and back), then a trip from my sister’s party to my mom’s house, and finally home.  I broke the trip into segments and measured each using the Google Maps directions feature:  (1) my house to my sister’s party: 4.7 miles city/5.6 miles freeway; (2) my sister’s place to the airport: 8 miles mixed/10 miles freeway (each-way); (3) my sister’s place to my mom’s place: 18 miles freeway; and (4) my mom’s place to my place 13 miles.  If I saved time and stayed on the freeway, I would drive just under 57 miles, which is too close to the 60+ miles that tends to limit my car on the freeway.  So, I favored city routes where it made sense, cutting the trip to just over 52 miles, and extending the range by three miles or so along the way (by driving a little slower). 

How did it turn out?  The extra city driving added about five minutes to each leg through town, which was easily managed and really did not impact my plans at all.  After driving the 52 miles, I needed to make two more errands near home, bringing the total trip to 55.7 miles according to the trip odometer.  So the car made it, but how much charge was left?  Driving home from the last errand, the gauge ticked down just a few hundred feet from home, leaving three bars (out of sixteen) on the charge gauge.  Typically, this is enough to drive another 11 miles on the freeway or up to 14 miles around town (the range gauge suggested 15 miles remaining).  So, all told, I could have safely driven 68 to 70 miles this day.  Fortunately I didn’t need to run the A/C on the car, or the results would have been different.

Good things come of people behaving badly

Somebody must have noticed the situation at work with the level-2 electric vehicle chargers.  Lately, the EV mailing list has been fired off with regular announcements of people leaving their car in the charging spaces after they have finished charging while others practically beg for a couple of hours of connection time.  (It doesn’t help that nearly all the convenient parking is now in use too, leaving disconnecting folks limited parking options.)  People are struggling to learn the new etiquette surrounding public infrastructure sharing.  We all struggle to find an opportunity to charge, but we seldom think about our impact when we fail to disconnect and vacate the charging space in a timely manner.  Sharing is a trait acquired in one’s youth when growing up with siblings, although this can also lead to hoarding.  Fortunately, the company decided to take the next step toward being a good advocate of electric vehicle adoption.

About two weeks ago, I noticed that a number of parking spaces near the employee entrance to the building had been roped off, and digging/trenching was underway.  I followed the route (visually) of the trenching and saw that it connected to the building and up to the roof (where the solar panels are).  I asked one of the construction crew members what the project was and they said they were working on installing four new charging stations with two plugs each, producing eight new charging spaces.  Added to the existing fourteen plugs and that amounts to more than 50% more charging points for us electric vehicle drivers.  Now, as I walk past the site each evening as I leave, I admire the new stations as they await final connection in the coming days.  Soon, we won’t have to depend quite so much on everybody’s etiquette and consideration.  I can hardly wait.

To charge, or not to charge

Anybody over the age of 30 remembers the first NiCad rechargeable batteries from the 1990’s.  These batteries needed to be depleted completely before recharging or they would “remember” how much you used and only recharge that amount in the future.  NiMH batteries got rid of the “memory” issue, but did little to improve charge capacity or battery life.  My first hand-held device had a Li-Ion battery and came with instructions to let the battery drain to 25% to 75% before recharging.  I followed that advice to a large degree and managed to get three years of useful charge from the battery before it started to dwindle.  I did not follow that advice for my laptops and those batteries all failed to hold the originally promised charge beyond two years.  With my first two cell phones, I was diligent about appropriate battery charging and managed to get more than four years of nearly full charge capability from each before the batteries started to degrade.

Five ticks remaining on the I-MiEV charge gauge (5/16)

So, before I even bought my electric car back in 2012, I knew how to better care for the battery.  Wait for the charge to drop below 75% full before recharging and avoid complete discharges when possible.  My commute usually draws the battery down to about 45% remaining, so this represents an ideal point at which to recharge the car.  But, when I know I will be working from home the next day, should I wait to charge the car or charge it right away?  The ideal choice for extended battery life (according to articles I have read) is to complete charging within an hour or two of when you expect to drive again.  The thinking here is that maintaining a full charge for an extended period strains the battery, ultimately weakening it.  But, the practical choice is to have the car ready to drive in case of an unexpected need the next day (which seldom happens for me).  So, I choose to charge at night and have the car sit fully charged the next day.

The real trouble arises when I use the car the next day to run a short errand and I use less than 25% of the battery capacity.  (Typically 85% to 90%of the charge will remain.)  Then I have to drive to work on the following day.  I admit that I like my comfort zone when it comes to the car’s range.  I don’t enjoy learning just how far I can push the car without running out.  While I can get to work and back and still have at least 25% of the charge remaining, it reigns-in my after work activities, limiting me to a short trip to a local store.  On the other hand, recharging with only 10% to 15% drawn off the battery will accelerate its decay.  When I know I need to do some extra driving I will recharge before driving to work.  When I have no plans, I drive on the reduced charge and hope for the best.  Sometimes, I have the option to charge once I get to work, which allows me to run those after-work errands.  To date, my efforts have paid off as I have lost less than 5% of the original driving range after 41 months of ownership.  (Mitsubishi warrants that 80% of the charge capacity will remain useful for ten years.)

Measuring Battery Degradation

One thing that I "miss" about driving my gasoline powered car is being able to calculate the fuel efficiency for any fill-up.  The math was straight-forward:  divide the miles driven by the fuel used to top off the tank and presto!  MPG.  Home EV chargers don't typically display the amount of electricity consumed during a charge-up cycle, so it's nearly impossible to compute the energy efficiency accurately.  There were a number of reasons for doing this with the gas car.  Most importantly was to understand how my driving habits impacted my fuel economy.  Secondarily, by watching for a drop in fuel economy I could detect problems in the engine that might otherwise have gone unnoticed.  A misfiring spark plug, a problem with the emissions equipment, or low (or burning) oil could all have a small impact on fuel economy (though newer cars have sensors for these problem areas).  So, why would I want to do this with an electric car?

Anyone who has used the same cellular phone for more than two years has noticed that the "talk time" starts to drop off after a few years.  Suddenly, sending a few text messages drains the battery faster than a phone call, and forget about doing anything beyond an e-mail scan using the internet, because the power will drain quickly.  Electric cars use a very similar battery technology, so it is logical to expect that the driving range of an electric car will start to drop off after a few years.  The manufacturers even admit to this storage decay in their warranty for the car's battery.  In my case, the warranty assures me that 80% of the original charge capability will be available after ten years.  So, how do you know if your battery charge capacity is dropping?

The charge gauge on my Mitsubishi i-MiEV is informative but lacks precision

To check your battery's capability, you have two options.  For those who are math averse, you can drive the car until the battery is depleted (or indicates about one mile of range remaining).  The problems with this approach are that it tends to leave you stranded somewhere, and completely draining the battery hastens its end-of-life, making the problem worse.  Enter mathematics ...  Instead of looking at the range, look at the distance traveled per kilowatt hour.  To measure this, you have to get an accurate reading of how much electricity was used to top off the battery, and how many miles were driven.  Then just track the miles-per-kilowatt-hour (or MPkWh) over time.  This way you don't negatively impact the battery's longevity (or strand yourself) in order to measure its performance.

It would seem that driving to work during Spring Break and March Madness on a Friday is the ideal time to find a vacant charger spot at work.  When I arrived at work, I had already driven an extra 16 miles from the day prior, so the range I could drive after work was already reduced.  Checking the ChargePoint network app, I found an empty charger spot right near the entrance to my office, so I parked there and hooked up.  One nice feature that public charging stations offer is a tally of the energy used to charge your battery.  (Often times this is used to calculate your billing.)  On this day I drove 36.5 miles and needed 7.589 kWh to recharge.  This yielded an efficiency of 4.81 MPkWh.  When the car was less than a year old, I was able to measure the same way and usually got about 4.95 MPkWh, which is within 3% of the other measurement.  This suggests that I have had no appreciable battery degradation in three years, which is comforting.  (This winter I was starting to think the range had dropped off more dramatically, but I lacked any solid evidence or numbers.  I guess it was just colder weather and stronger winds.)

A little traffic, please?

When I would drive my gasoline powered cars, I would dread having to drive through congestion on the freeway.  Not only was I slowed by the traffic mess, but the car ran less efficiently, it was a little jerky on the frequent stop-starts, it was irritating listening to the engine idling or running at low speeds, and there were the exhaust fumes, from my car and the others around me.  And, in the summer, all those hot engines running seemed to make the freeway steam in the sun.  I always looked forward to the traffic break when I could again cut through the air at high speeds and the car was running near its peak efficiency.  So, why would I want to endure highway traffic congestion now?

Electric cars today lack a multi-gear transmission, which allows a gasoline engine to operate at both low and high speeds, while optimizing for the latter.  Generally, gasoline engines are rather inefficient at lower speeds, and they require a clutch mechanism in order to stop and resume, robbing the engine of its abundant power.  The electric car has just one speed, directly connected to the wheels because it can start turning from a stop.  Lacking other gears, the electric motor is less efficient at typical freeway speeds.  In short, the electric car can drive much further on the same amount of electricity at lower speeds (such as found in most highway traffic congestion).

My commute - 12 interstate miles and 7 expressway miles

Today was a case in point.  My drive to work consists of 12 miles driven at 55 to 60 MPH on the freeway, followed by 7 miles driven at 45 MPH on an expressway.  Lately, by the time I return home at the end of the day (38 miles late), the ninth (of sixteen) power bars in the charge gauge has disappeared.  Because of my work hours and meetings, I typically commute after much of the heavy traffic has subsided.  Today, however, was different.  I had to leave earlier for work and dealt with congestion along half of the freeway route to work.  I also drove home early and had to deal with a brush fire and two accidents along the way, which backed up traffic for nearly the entire stretch of the freeway I travel.  I also ran a few errands after arriving at home.  By the time that the charge gauge had dropped its ninth bar, I had driven 44 miles (or 15% farther).  So, I saved nearly 1.5KWh of charge by driving in congested traffic.

So, the efficiency is greatly improved in the slower moving traffic.  What about the other issues I face in congestion?  The interior noise in my car is dramatically reduced because there is no roaring engine (especially while idling).  Every start from a stop is delivered with silky smoothness thanks to the low-end torque available in an electric motor.  I am able to save a little time by using the carpool lane instead of being stuck with the rest of traffic.  And, of course, my car is not producing any exhaust gas fumes (and its electric charging is offset by solar power, both at home and at work).  If there were many more commuters also using electricity instead of gasoline, we’d all enjoy the drive home a lot better.

Kids and the i-MiEV

I think Dr. Seuss had a hand in designing the newer electric cars (except for the Tesla, which has serious Jaguar design influences).  I drive the Mitsubishi i-MiEV, which is odd-looking at best.  And the Nissan Leaf is no better.  And BMW tried to give the new electric i3 a real sense of style, but missed the mark in my opinion.  While the Fiat 500 has a little bit of cute-ness going for it, its cramped rear quarters makes it an impractical choice for many.  And the Think City, the Scion iQ, and the Smart are just as peculiar to look at.  Surely these cars are examples of Dr. Seuss’ design works.  At least the i-MiEV has an ample interior.  A number of my passengers have remarked how they were surprised that the car has as much interior space for how short it is outside.  And, with four doors, that interior space is easy to get to.  (The i3 is similarly useful inside.)  But it seems that the biggest fans of this car are kids.



Dr. Suess' design influences

Dr. Suess' design influences

 

I have a niece and nephew (seven and five years old) who actually enjoy the car and its funky look on short trips.  They call it the “Purple Car”, which is the same color as their favorite afternoon hangout in San Jose - the "Purple Building" (also known as the Children's Discovery Museum).  Sometimes they call the car the “funny car” – I’m guessing because of its looks.  Of course funny car is both a compliment and a slap in the face from them.  Funny is endearing and welcoming, which I believe was Dr. Seuss’ goal in the design of all of his characters and their possessions.  The only problem here is that the people forking out hard-earned money for these cars are no longer children.

The BMW i3's awkward styling

Here is my theory on why electric cars look so off from normal.  Most normal looking cars attract a lot of buyers.  Sexy looking cars attract buyers in droves.  Only the price of these sleek looking sedans keeps the buyers at bay.  So, why aren’t electric cars sexy looking and affordable?  Manufacturers can only build so many electric cars in their early production runs (typically fewer than 10,000).  So, they need to reduce the demand for these cars.  There are two approaches: raise the price or mess with the looks.  Unfortunately, early electric car buyers have been very value savvy, so a jacked up price had better offer superior value (which is very hard to deliver).  So, rather than following Tesla’s expensive lead, manufacturers follow the alternative and lean on styling to dissuade most buyers.  Only those drivers with a sturdy constitution can find themselves heading down the street in a bug-eyed, Picasso-styled driving machine, allowing the manufacturers to meet the demand comfortably.  I expect that the volume electric vehicles to come next will be much easier to look at and be seen in.  (Check out the Chevy Bolt.)