What's Holding Back Electric Car Sales?

[Zythryn]

As for the range vs number of chargers, if you double the range you will need fewer than half the chargers.

That's a very difficult, and probably wrong, thing to determine. It's pure guess-work unless you understand the true usage profile of the users.

I agree for any individual.
However, in total, for the entire market, I am quite confident that would hold true.

In my case, if I had an 80 mile EV I would be using a public charger 1-2 times a week during the summer, and 3-4 times in the winter. With a 160 mile EV I would need to charge once a year.
That is for city travel. Vacations would be close to the half mark, just slightly less.

I'd be interested in others experiences though. Perhaps I'm the exception rather than the rule?

 

[GetOffYourGas]

As for the range vs number of chargers, if you double the range you will need fewer than half the chargers.

That's a very difficult, and probably wrong, thing to determine. It's pure guess-work unless you understand the true usage profile of the users.

I think it depends more on whether you are taking the perspective of the network (i.e. chargers to cover an area) or the driver (i.e. charging stops on a trip).

Simplistically speaking, we drive our cars on the 2-dimensional surface of the earth. If the distance between chargers doubles, the number of chargers necessary to cover the same area decreases by a factor of 4.

On the other hand, for a driver on an infinitely long trip, you are driving in one dimension, and will need half as many chargers. Of course, the first charge is "free" since it is from home, so you do need slightly less than 1/2 the chargers.

 

[donald]

Simplistically speaking, we drive our cars on the 2-dimensional surface of the earth. If the distance between chargers doubles, the number of chargers necessary to cover the same area decreases by a factor of 4.

On the other hand, for a driver on an infinitely long trip, you are driving in one dimension, and will need half as many chargers. Of course, the first charge is "free" since it is from home, so you do need slightly less than 1/2 the chargers.

This really isn't correct.

You might need to take only half the stops with double the battery, but you have to wait twice as long to charge. So, overall, the time on chargers is not a function of the battery capacity but a function of the miles you do, and the limitation in a scenario where there is a large population of EV drivers is how many charging sessions you can get out of a charger in a day.

One driver with 2.N.kWh battery on an infinite trip would, numerically speaking, use a half of the chargers that another driver with N.kWh battery, but he'd be sitting on each for twice as long, so the total number of chargers that a large population of drivers need would be exactly the same, assuming the same mi/kWh, because the limitation is time-on-chargers not whether there is a charger there.

(And there has to be a large population of drivers else there is no point in putting up a charging network!)

So-many chargers have so-many charge-minutes per day between them, and whether a population of cars with small batteries use them in twice as many charge sessions as large battery cars, there are only so-many kWh they can put out in the day, and therefore only so-many EV miles.

But in fact carrying around an extra N.kWh would probably hit your mi/kWh figure, so it is possible that the folks with larger battery capacities might actually need MORE chargers, not less.

In practice they would need less because they can get further on their first 'leg' of the journey and that cuts out 'one charge', and such lengths of journeys occur more often than longer journeys. It is the elimination of 'the first charge' that is the main benefit. The whole calculation is dependent on some integer maths and how many miles the cars are actually expected to be used.

Put it another way. Say there are two chargers on a route and all these N.kWh cars are using them. All of the drivers move to 2.N.kWh cars and say between themselves 'hey, we have twice the capacity, we can get rid of one of the chargers'. Now you have all the drivers turning up to the one charge point instead of being split between the two, hence you will need to double the number of chargers at this, new, singular location. Outcome, yeah, half the number of charger locations, but still the same number of chargers.

Your logic only works if you are going on the basis that the chargers will not be saturated in use, and that most people only need one charge between their origin and destination. That might well be true in a majority of cases, but there is nothing certain about it.

 

[DaveEV]

As for the range vs number of chargers, if you double the range you will need fewer than half the chargers.

That's a very difficult, and probably wrong, thing to determine. It's pure guess-work unless you understand the true usage profile of the users.

I agree for any individual.
However, in total, for the entire market, I am quite confident that would hold true.

It certainly seems that the Tesla Supercharger network has far more capacity than the CHAdeMO network here in the USA.

Perhaps it only seems that way because Tesla installs 6-8 stalls at your typical location, but let's just compare CHAdeMO to Superchargers in California:

17 Supercharger locations, 125 stalls (more if you count locations under active construction), each pair of stalls is capable of 120 kW, so that's 7.5 MW of charging power.

Looks like 194 individual CHAdeMO plugs, let's say each is capable of 40 kW on average or 7.8 MW of charging power.

So the question is - how many Model Ss are there in California compared to LEAFs?

So the Model S has about 3x the range of the LEAF - does that mean it should only have a third the charging stations?

Not quite an apples to apples comparison - if CHAdeMO stations were grouped together with 2-4 plugs per location instead of being scattered about haphazardly, we probably could get away with a lot fewer stations as they might actually be reliable. And there is evidence that many Tesla Supercharger locations suffer from overcrowding as it is already at many locations - Gilroy, Hawthorne (currently getting upgraded to 13 Supercharger plugs + 8 HPWC plugs - over 1MW of power!), San Juan Capistrano, not to mention the 10 Supercharger locations coming soon (another 60 plugs or so).

Still - IMO the biggest holdup for electric car sales is:

1. Range - 100+ miles range at 75 mph with a 20% buffer (so a 140+ mi EPA vehicle)
2. Charging infrastructure - Need to have reliable charging spots at reasonable intervals. With the current LEAF that means 40 mile intervals at a minimum along highways - might be even closer given than a 10-bar LEAF can probably only drive 35 miles on a 80% charge to LBW. But in highly populated areas you probably want charging stations even closer together so that one has the assurance that they will be able to charge if they need to to make it that last 10-15 miles home if they need it and run low. Now for that last situation even 6.6 kW would work in a pinch - 30 minutes gets you 15 miles of range or so.

 

[GetOffYourGas]

...

Your logic only works if you are going on the basis that the chargers will not be saturated in use, and that most people only need one charge between their origin and destination. That might well be true in a majority of cases, but there is nothing certain about it.

I follow what you're saying, Donald. Everything you described is true if the charging power (kW) is constant. However, a 2X capacity battery can handle a 2X charging power. In other words, if the charger can provide it, both cars can charger in the SAME amount of time. Since the current generation Leaf maxes out at 48kW (a "2C" rate), and the CHAdeMO standard can provide 100kW, I would say it's safe to assume that a 2x capacity relative to today's 24kWh battery should still charge in the same time with the right charger (maxing out at 96kW - again 2C).

Now that argument obviously breaks down if we talk about Tesla, but I think it holds pretty well for most of the affordable BEVs on the market today.