06 December 2010

The one thing electric cars need most but no one is offering

Every electric car, no matter the manufacturer (or start up), is offering one and only one power inlet.

Is this the only way it could be?  Gas cars have only one filler pipe for the gas tank.  So electric cars should have only one power receptacle, correct?

Wrong!  At least in the USA.  Much of the world has 220 volts as their standard supply voltage, which makes for a faster charging process.  But in the USA we stayed with 110 volts even after light bulbs switched from carbon filaments to tungsten one hundred years ago.  Since wires are more or less the same diameter in European homes as in US homes, this means there is less power available from US outlets, even if they are nominally safer.

There are many places in the US where it is easy to find multiple electrical outlets near each other that are on separate circuits. I always used two circuits in my garage in winter, one for charging the Mini E and one for keeping the cabin warm, which helps improve the battery performance greatly.  (Of course the charging circuit was usually the 220 volt wall box and the heater was on 110 volts, but bear with me.)

At my work place in the winter, I used two separate, dedicated 110 volt circuits.  One for charging, one for heating the car.  I have done the same thing when stopping to charge at the homes of several other Mini E drivers.  Plug the car into the charging box and run the cabin heater to a regular outdoor receptacle.

I have seen three separate 110 volt outlets at multiple shopping centers that have reserved parking spots for electric cars.  Truck stops with the "Idle Aire" system provide three 20 amp outlets right next to each other, all on separate circuits.  All sorts of camp grounds have multiple circuits side by side.

There is no reason not to provide a second connector, designed into electric cars, so that you can either run the cabin heating or cooling WHILE charging from a separate circuit, or simply double the charging rate if both circuits are 110 volts.

How to protect against someone plugging two cords into the SAME circuit?  This is a very easy engineering task.  If two circuits are out of phase with each other, they are guaranteed to be on different circuits.  This was the case I had at work, this is the case with "Idle Aire", and the shopping center parking lots.

So, why not provide even more than two power inlets on an electric car?  Actually the limit would be three.  In industrial or commercial locations where power is generally supplied in three phases, three would be the maximum that could be definitively distinguished from each other, and thus verified to be on separate circuits.  Idle Aire provides three outlets right next to each other, all on separate phases. Same in the shopping center parking lots.  The two outlets I had access to at work were on different phases of a three phase supply, although I did not get around to finding a third circuit.

In the long run, two (or three) power inlets in an electric car might not be necessary, but in the short run it strikes me as essential for flexibility.  And I don't hear any one talking about providing it.  This is an engineering crime of omission.  I cannot think of another thing that would improve the flexibility and even viability of early electric cars more than multiple power inlets.

And best of all, I don't see anything in the National Electrical Code or recommended practices of the Society of Automotive Engineers that forbids it.

So here is how it would work.

1) Plug in the first cord, the car starts charging.
2) Plug in cord number 2, and if the car can verify that the circuit is separate from the first, you either double your charging rate or use the added power to heat or cool the cabin, as you choose.
3) Plug in cord number 3, and if the car can verify that the circuit is separate from the first, you again increase your charging rate.

I understand that the coming BMW electric car will heat or cool the cabin from "shore power" but only after the battery is fully charged.  With a single 110 volt supply, that is about all you can do.  But with two circuits, it could be extremely useful at times to condition the cabin temperature BEFORE charging is complete.  I speak from experience.  25,000 miles of electric car experience in the Mini E, to be precise.  Much of it in cold weather.

There is a commercially available safety device that can combine two 110 volt outlets into a single 220 volt outlet.  But for practical purposes, it would be of limited use for an electric car although I have heard of a Tesla driver using one effectively.  These devices are popular for, say, contractors that need to operate a 220 volt floor sander in an older house, or operation of European instrumentation in a US facility.  But for outdoor use with an electric car, the omnipresence of Ground Fault Interrupters (GFIs) makes this "Quick 220" box unusable for the average electric car driver.  It only works without a GFI.

However, a properly engineered electronic interface in an electric car could easily take advantage of multiple separate 110 volt circuits to get faster charge times without special infrastructure installations in the early days of electric cars.  And I don't hear anyone talking about it!  Why?  Has no one noticed?  Are you guys asleep or something?  Hello?  Is anybody out there?  Don't make me do it myself!

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