Short range electric cars taking longer trips with faster charging

An electric car with just a 50 mile range can barely be used around town, right?  That’s what conventional wisdom says:  that a short range electric car is useless because the range is too limiting. What if the real limitation is charging speed, and you couple the short range car with a fast charger?

My car is one such vehicle. It’s a home-built conversion based on a 1971 VW Karmann Ghia that’s so pretty people routinely stop to gawk, especially after they learn it’s electric. My budget only allowed for 14 kilowatt-hours of battery capacity, giving the car “only” 50 miles of range. Conventional wisdom says I would be limited to short trips around town, but I’ve been able to repeatedly take medium length trips (200+ miles per day) without trouble.  How?  I have a 40 amp (8-9 kilowatt) charger on-board, giving a faster-than-average charging rate.  I know where the charging stations are, and I’ve developed confidence in the equipment from taking several medium-range trips.

I’m taking a medium range trip (Santa Clara CA to Laguna Seca Raceway, and back – a 170 mile round trip) and hope that by demonstrating how I do this others might learn how to transcend supposed electric vehicle limitations.   We don’t have to remain trapped by range anxiety fears.   These ideas apply to owners of electric cars with longer range, and while some of the details will be different, the basic concepts will hold.

The destination is Laguna Seca International Raceway, a race track that’s been the site of several significant achievements in electric vehicle racing.  One such is the REFUEL race that’s now in its fifth year. That event is pretty low key, and is really just a chance for a track day for electric vehicle owners.  In its first two years most REFUEL attendees were driving/riding electric conversions.  The manufacturers hadn’t yet started making the LEAF or other electric vehicles, but over the years REFUEL has become a concrete demonstration of the rapid advances in electric vehicle adoption. Now, REFUEL has been taken over by manufactured electric cars, with Tesla Model S’s taking the limelight.

Some principles I discuss below are:

  • During the trip you need to be either charging, or driving
  • Don’t charge to 100% because the tail end of the charge is very slow and drawn out
  • On multi-hop trips, at each charging location add range a little longer than the upcoming leg
  • Having something to do during charging stops means the charging stop is not a waste of time
  • Know your charging equipment
  • Map the route carefully, knowing the primary charging stops and backup stops in case of broken charging stations


My first leg is to drive from Santa Clara to Gilroy, CA, to use the charging stations at the outlet mall. Tesla Motors chose this spot for one of the earliest Supercharger installations, making me properly envious at the charging speed Tesla owners enjoy.

I’ve driven 35 miles, and have 28 miles to go before my next stop in Salinas. After that I have 14 miles to get to the track. Both those segments have mountainous stretches.  The total miles (77 miles) is more than the range of my car.  The question is, how much charging should I do to arrive safely, and how do I minimize the charging time to arrive at the event early?

Because my car is a home-made conversion I have more flexibility than do the manufactured cars.  Such as, to install a more powerful charger.  The Manzanita PFC40 in my car can handle 40 amps, and because most commercial charging stations run at 208 volts that works out to 8.3 kilowatt charging rate maximum.  That’s significantly faster than the typical 6.6 kilowatt charging of the manufactured electric cars.  I can only charge at that rate if the charging station can dish it out, and unfortunately many charging stations (cough cough Blink, Chargepoint) cannot.

I’ve previously validated the Gilroy charging stations can handle 35 amps, and I’ve set the knob on the Manzanita to that amount.  That’s roughly 7 kilowatts.

The rule of thumb is for a 6 kilowatt charging rate, an electric car gains 20-25 miles of range per hour of charging.  I use that rule of thumb to calculate the charging time required to cover a given trip.

In this case I want to charge long enough to be certain of having the range to reach Salinas, the next stop, 28 miles away.  My car has roughly 15 miles of range remaining, and the next leg of the trip is mountainous and therefore will require more energy.  Adding 28 miles would require over 1 hour charging time, while adding 13 miles (and arriving in Salinas on empty) would cut that to about 1/2 hour.

I could charge to full, have a 50 mile range, and just drive straight to Laguna Seca which is only 42 miles away.  However, there are two reasons that wouldn’t an efficient use of time.

First, charging  the last 5-10% always takes a long time because the charging rate naturally slows down.  To make the best use time, you want to be charging at the highest rate possible.  That means not taking the time to charge the vehicle to 100% but to charge to 90%.  By charging up to 90% your vehicle is still gaining range at the fastest rate possible, while charging beyond that point slows your effective speed.

Second, the charger at the Rabobank in Salinas can dish out 70 amps of power.  Therefore, at that station I can turn the Manzanita up to a higher charge rate (40 amps) for an even faster effective speed.

A lot depends on the distance covered in your next leg.  You have to charge the vehicle enough to handle the next leg of your trip, plus a few extra miles which will be your cushion in case something goes wrong – such as a broken or missing charging station.

I elected to charge for about 40 minutes.

The Supercharger stations behind me charge at 100+ kilowatts rate for about 300 miles of range per hour of charging. The 6 kilowatts my car is sucking down is a paltry 20-25 miles per hour of charging.  I’m really wishing I could afford a Model S but that desire will have to wait for the Model III in 2017ish.

Now I’m at the Rabobank in Salinas.  Because the car is in an indeterminate intermediate state of charge, I don’t know precisely the remaining range in the pack.  Maybe it has enough range to get to Laguna Seca, but I don’t want to risk getting stuck in the mountains.

The distance to go is about 14 miles and using the rule of thumb that means about 1/2 hour of charging.

If there were no charging available at Laguna Seca, the required range would be double – or about 30 miles, because I’d have to drive back to this charging station.  But in this case I know that at the REFUEL event there will be plenty of charging available, and I’ll be able to charge the car to full before leaving.

Therefore, I only have to get to the track and can even arrive with an empty battery pack.  Well, not too empty, because the entrance to the Laguna Seca Raceway is a steep 16% grade climb for about a half mile, and the car will need some power to make it up that last hill.

I’m feeling urgency about getting to the track.  Rather than wait the full 1/2 hour, and assuming the car has some significant remaining range, I’ve only charged for 20 minutes.

I easily made it and the car never showed a sign of the battery pack running low, even on the climb into the race track.

As expected I was able to find a charging outlet, except that we had to first untrip a circuit breaker.  At first I only had a 120 volt outlet on which to charge, but later in the day after some people left there were some 240 volt 50 amp outlets available.   With that power I’m able to turn the Manzanita PFC40 to full, charging the car fully.

What about the waiting time?  Charging my car fully at the Gilroy charging station takes about 1 hour 50 minutes (I’ve done this several times).  This time charging to full at the race track took quite a bit longer, because of how long it had been charging at 120 volts (at a 1.5 kilowatt charge rate versus 8+ kilowatts).

The waiting time doesn’t matter if you naturally have something else to do.  For example, across the street from the Gilroy charging stations is a Denny’s Restaurant, and next door is an In-N-Out burger joint.  I could have had a meal at either one.  Instead I spent that time writing the first draft of this blog post, and taking pictures of the Supercharger station.   At the Rabobank charging station, I had a snack from food I was carrying with me, but could easily have gone into the Taqueria or other food joints in the shopping center.

At Laguna Seca, the total charging time was probably 3-4 hours but I didn’t notice it.  That’s because I was too busy talking with people and taking in all the activities of the REFUEL event.

In other words, the charging time is of no importance if you have something else to do during that time.

In the typical example – the daily commute to/from work – you may have a 3-4 hour recharge time after arriving at work.  You might think, ugh, what a burden that is, but the only cost to your time is the minute (or less) it takes to plug in to the charging station.  You plug in, walk away, take care of your business, and it doesn’t matter that it took the car 4 hours to recharge.

It didn’t matter that I spent nearly 1 1/2 hours of charging time to get to Laguna Seca.  I had other things to do with that time.

The return trip home was uneventful, and was just the reverse of the trip above.

At the Salinas charging station I elected to only charge for 15 minutes.  The car was full at Laguna Seca, so it was almost unnecessary to even stop in Salinas.  I wanted to use the faster charger so it might decrease the charging time required in Gilroy.

In Gilroy a longish charging session was needed because there simply wasn’t enough range to make it home.  Since returning home to my sweetie was highly important, getting a full recharge wasn’t needed, and I could arrive with an empty battery pack letting the car charge all night long.

In Salinas there’d been about 35 miles remaining range, and the 15 minutes charging brought it up to about 40 miles.  In Gilroy the remaining range was about 10 miles (to be on the pessimistic side), and there was 35 miles to go.  That meant a 1 hour charging time, while sitting in the Denny’s having dinner and writing notes about the REFUEL event.   During the return trip, I would have spent that time anyway to have enough details in my mind to write the REFUEL event report.

About David Herron

David Herron is a writer and software engineer living in Silicon Valley. He primarily writes about electric vehicles, clean energy systems, climate change, peak oil and related issues. When not writing he indulges in software projects and is sometimes employed as a software engineer. David has written for sites like PlugInCars and TorqueNews, and worked for companies like Sun Microsystems and Yahoo.
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About David Herron

David Herron is a writer and software engineer living in Silicon Valley. He primarily writes about electric vehicles, clean energy systems, climate change, peak oil and related issues. When not writing he indulges in software projects and is sometimes employed as a software engineer. David has written for sites like PlugInCars and TorqueNews, and worked for companies like Sun Microsystems and Yahoo.

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