We Need a Standard Metric For DC Fast Charging Speed, Similar to MPG.

[pdx_m3s]

Charge ratio is good, but I think we also need a metric for charging speed. My suggestion would be miles added per minute, on average, over a 10->80% charge session. This way manufacturers can’t play games by only quoting miles added per minute during a very narrow SOC.

 

[jerry33]

The only time charging speed matters is on a trip (with a few exceptions) and, except for a lot of routes in the central states, charging stops are 100 to 150 miles apart, the only real criteria is "will there be enough charge gained in fifteen minutes to continue without white knuckle passengers?". Fifteen minutes are chosen because it's unusual to stop for less than fifteen minutes regards of car type. The problem with this method is winter which has much higher energy usage, so charge times are longer. The other factor is the miles remaining when starting to charge, which needs to be standard. SOC doesn't work because of the variance in battery size between cars. (25% of a 370 mile MS is much more than 25% of a 220 mile Leaf). I believe most people would be comfortable with fifty miles remaining when they arrive at their destination, assuming no problems. The fifty miles is to take care of any issues that might occur (weather or traffic related). So instead of the ICE cars' city vs. highway BEVs should have a winter charge time vs summer charge time to recover 150 miles. Combined isn't applicable.

 

[ecarfan]

My point is that, if you go on a road trip in an EV, you have the option of arriving at your destination (or nightly stop-over point) with a relatively low SoC, just as you can do at the end of a day of commuting and running errands. This option reduces the need for high DC fast charging rates, and by a quite significant amount.

It depends on your definition of the length of a “road trip”. I think that the very cogent analysis by @Zoomit is on point in terms of driving from SC to SC, and applies to trips of 400 miles/day or more (which many people do). I agree with you that for a “road trip” of say 400 or less your point is valid, except...

As to "no planning is required to find a Level 2 plug at night," those are becoming quite common, and I wouldn't be surprised to start seeing them noted on highway signs that announce lodging before too long. This will make finding them trivially easy. Even now, you can find them with PlugShare without all that much effort.

Yes, you can find them, but PlugShare does not tell you if they are properly maintained and in good working order or if they are in use. Since L2 charging points are usually available in very low quantities at a specific location (one or two plugs) you cannot count on them. The situation is improving, but slowly. Superchargers are much more reliable.

 

[jerry33]

Yes, you can find them, but PlugShare does not tell you if they are properly maintained and in good working order or if they are in use. Since L2 charging points are usually available in very low quantities at a specific location (one or two plugs) you cannot count on them. The situation is improving, but slowly. Superchargers are much more reliable.

Certainly Superchargers are more reliable (as are destination chargers), but there are many places where there aren't Superchargers, or they are too far apart, or there is no redundancy. For example, a few weeks ago the Salina, KS Supercharger worked but couldn't be reached due to flooding--the only road to it was barricaded (probably didn't help Holiday Inn's business either). Because there are no SCs between Salina, KS and Lincoln, NE (a distance of ~200 miles), alternative charging locations needed to be used. Superchargers can't be 100% relied on until the network builds out enough so one incapacitated SC location doesn't force alternatives. That is still a very long ways away (unless you only travel in California).

And while PlugShare doesn't tell you, if you are using a private location, you have to call and reserve, and sometimes people leave notes on PlugShare about their experience at a particular location. As a last resort, you can call and find out. Also not every possible location is in PlugShare. PlugShare does a poor job of showing RV parks, so you also need to check RVparking.com to see those locations.

 

[M3BlueGeorgia]

MPH (or KPH) is the only useful metric.

Amount of power added (kWh) is useful when different charge technologies are used on the same car, but once you start comparing different cars with different rolling efficiencies, MPH (or KPH) is what really counts.

 

[Evbwcaer]

I see the value in the ratio, but I don't think that will register with Joe Schmoe car buyers. The ratio is a really useful number, but I think it is hard to understand.

Call me arrogant, but I still think my metric is the best because Joe Schmoe knows what minutes are, and minutes are comparable across all brands.

Car buyer, "How long does it take to charge on road trips." Dealer, "10:1".

Car buyer, "How long does it take to charge on road trips." Dealer, "25 minutes."

Twenty to Two hundred Time, TTT, becomes a Monroney sticker listing, just like MPG, GVW, MSRP.

 

[nwdiver]

As EV's become mainstream, purchased by "normal" people, not just EV enthusiasts,

You think Miles per Gallon made any sense to people coming from a horse? Or Megabytes to people coming from file cabinets full of paper? kW and kWh is fine. 'Normal' people just need to learn how 'new' technology works.

 

[RubberToe]

I did see someone mention summer versus winter, but a couple other very important items haven't been discussed yet...

How would one take into account "battery pre-conditioning" when computing the 20-200 or whatever metric is proposed? Tesla can now do this, so do you allow in your metric for the Tesla pre-conditioning for some time on the road prior to arrival at the Supercharger? If Tesla changes their pre-conditioning software with an update two years after a car is sold, does it get a new 20-200 "sticker"? If the 20-200 is only calculated on a new cars battery, does that provide any useful information for someone buying a 5 year old used Leaf that might be ready to die? Or would you require a 20-200 test as part of the vehicle transfer paperwork?

Also remember that Tesla Superchargers are "proprietary" chargers. They do not support either of the standard CCS or Chademo connectors. So maybe if the government is involved, they only allow the 20-200 to be calculated on standard connector/EVSE equipment. In that case, Tesla's would need to use an adapter, and possibly restricted to the maximum power output by a non Supercharger. This might seem illogical, but the Volkswagen Dieselgate settlement that created Electrify America only requires them to support non-proprietary connectors, so no EA EVSE had a Tesla connector. And this despite the majority of EVs on the road being Tesla's.

I'll concede that this is an important thing to pursue, though mostly for those newbies who don't get that you have to stop for 15 minutes every few hours for other reasons.

Joe(sephine) six packs only question might be something like: How long does it take to fill up? If the answer to that question has to be the 20-200 time, then you will find that other automakers will whatever is required to "game" the test to get the best possible number. See the emissions scandal if you don't agree with this.

Tesla is obviously going to have the best score on any test that is dreamed up, so the other companies will either game the test or simply run commercials with factual data spun to make them look better. For example: "This great Smart Mini charges to 80% in 15 minutes, even a Tesla can't do that"! With no mention that the battery capacity is 20% of the Tesla battery.

If there is no defined 20-200 standard test required, every company will devise their own metric/test that will convince everyone their car is the best. The i-pace, e-tron and Taycan being less efficient than a model 3 will demonstrate this principal at work.

RT

 

[Evbwcaer]

You think Miles per Gallon made any sense to people coming from a horse? Or Megabytes to people coming from file cabinets full of paper? kW and kWh is fine. 'Normal' people just need to learn how 'new' technology works.

How are kw and kWh fine? Those values alone tell you nothing? You need a rate/time.

 

[nwdiver]

How are kw and kWh fine? Those values alone tell you nothing? You need a rate/time.

They tell you just as much as HP and Gallons....

 

[SSonnentag]

I think stating 3 average miles/hour or km/hr would work well:

1) 5%-20% average mph
2) 20%-80% average mph
3) 80%-95% average mph

The data sheets for each vehicle could read something like:

15/60/15 Charging Rate: 100/300/90 mph