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Electric Vehicle information for Atlanta and Georgia

DC Fast Charging

DC Fast Charging cabinets in service in Atlanta market

DC Fast Charging (DCFC) is a class of technology that can charge your car much faster, on the order of minutes rather than hours.  Widespread rollout of DCFC stations is the true game changer in the automotive market, because with DCFC, EVs get over the last hurdle — quick “fueling” and long distance travel.

The current (ha) problem is that there are three different, competing DCFC plug types.  Back in 2009, the automakers agreed on the Level 1 and Level 2 standard, and now that’s the J1772 receptacle that you see on all cars and the J1772 plug that you use at home to charge overnight.  But they did NOT agree on the Level 3 / DCFC standard, and since then the market has been churning, trying to sort out the winners and losers.  (FYI, the correct term to use is DCFC, not Level 3, for reasons I won’t go into here.)

So there are now three DCFC plug standards on the market.  In 2010, Nissan launched their Leaf with the “Chademo” plug standard (now also seen on a few other Japanese and Korean cars).  In 2012, Tesla launched the Model S with their proprietary “Supercharger” interface, and that’s now on the Model X as well.  In 2014, the rest of the auto industry, via the Society of Automitive Engineers standards organization, agreed on the “SAE Combo” plug standard (first seen on the BMW i3 but now also a half-dozen other cars).

They are generally NOT compatible with each other.  A car with one kind of receptacle will not work with another kind of plug.  The one exception is that Tesla, at great effort, designed an adapter to allow Tesla cars to use Chademo stations.  But that’s just one of the six possible interoperability combinations.  Non-Tesla cars can NOT use Tesla stations.

The good thing is that it’s now been a few years since this standards battle started, and we’re starting to see market convergence.  Nissan’s partner Renault is shipping their new Zoe car with SAE Combo, so this may signal the eventual end of Chademo.  Tesla has joined the SAE Combo industry organization, which may signal that Tesla will upgrade their vast Supercharger network to support SAE Combo cars.  With every month there’s a new tidbit of news that shows that the market is converging.

In 2014, the Atlanta market started to see a lot of DCFC sites popping up, some with just one of the above plug types, and some with two. The next section serves to document the different kinds of DCFC cabinets seen in metro Atlanta.

See the bottom of the page for data on the charging rate (power) of different cars.

picture manuf. network plug type(s) power Plugshare example note including date first seen in Georgia
DCFC-Blink Blink? Blink Chademo only 50 kW none Jul 2013; two plugs, power split; both Georgia units replaced
DCFC-Eaton Eaton misc Chademo only 50 kW none Nov 2013; can do SAE Combo but not seen in ATL yet; both Georgia units replaced
DCFC-NRG Sumitomo NRG Chademo only 44 kW Town Center NRG EVGO launched in Atlanta market in November 2014, although these stations were widespread, found at most Nissan dealers prior to that
Georgia-Power-branded-DCFC Efacec Chargepoint Chademo and SAE Combo 50 kW Georgia Power HQ Nov 2014 testing, Jun 2015 launched
Signet-Greenlots-DCFC Signet Greenlots Chademo and SAE Combo 50 kW Cobb County April 2015
Signet Greenlots? Chademo only 50 kW Nissan in Griffin April 2015; same as above but equipped with only Chademo port
BMW-ChargeNow IES/Bosch Chargepoint SAE Combo only 24 kW BMW office Jan 2015; some only deliver 21 kW; BMW/VW partnership
NRG-BTC-DCFC BTC Power NRG Chademo and SAE Combo 50 kW? AAA storesSuwanee April 2015; can run off 208V 3-phase power; output cable may be limited to 100 Amps, which limits peak power to about 40 kW
ABB ABB NRG Chademo and SAE Combo 50 kW Perimeter Summit Nov 2015
Tritium-Veefil Tritium Veefil Chargepoint Chademo and SAE Combo 50 kW GWCC downtown Nov 2015
And finally, in a class of their own …
Tesla Inc. Tesla owners only Tesla cars only 120-135 kW pedestals, cabinet May 2014; much better tech than anyone else, but for Teslas only; two pedestals per 120-135 kW cabinet; see links to left for lots of pictures, and more cabinet pictures

DCFC station attributes to consider:

– which DCFC plug standard? e.g Chademo only, or dual-standard with both Chademo and SAE Combo
– what is the peak power? 21 kw, 50 kW, 130 kw … HUGE difference in charge time
– for Chademo, which plug type exactly? old clunky Yazaki CHV-03 “firehose” design, or newer designs? Yazaki CHV-04, Sumitomo, JAE, see pics
– dual-standard cabinets effectively serve all three DCFC types, since Tesla can use Chademo
– is the DCFC a split design with separate cabinet and kiosk, or single unit?
– cabinet size? contrast Efacec vs Signet
– is it prone to overheating? do the filters clog?
– does it accept input power as 480V/277V 3-phase or 208V/120V 3-phase? service install expense vs current (amperage) needs

DCFC station technology developments that are in the pipeline:

– 150 kW peak power capability — standards work completed, products coming*
– 350-400 kW stations — in the works
– stations that have multiple plugs being able to supply power on all of them simultaneously, splitting power somehow*
– liquid cooled charging cables to allow higher power flows
– cars that can absorb more than 50 kW*; Chevy Bolt EV absorbs 80 kW
– cars that run at ~800 Volts instead of ~400 Volts, which alone could double charging power rates
– U.S. electrical code (NEC) revising the “HV threshold” from 600V to 1000V, which would allow consumer handling of 800V cabling
* Tesla already does this

BMW i3 DCFC charging power curve


This graph was generated from data gathered in early 2015 during DCFC sessions at stations with SAE Combo plugs. Most of the sessions were done at stations that deliver peak power of 50 kW; the lower curve sessions were done at a 21 kW station. The middle curves were typically sessions done at a 50 kW station that was delivering only 36-37 kW; typically this degraded power will be due to high ambient temperatures or a current limit in the station’s input or output.

The first key threshold to note in these curve is what SOC the car starts ramping down the power that it can absorb. On the i3 with the 22 kWh battery, it starts ramping down from 50 kW at around 55% SOC.

The second key threshold to note is what SOC the car is absorbing less than 6-7 kW. At that point, the car is charging as slow as it would on a regular Level 2 (J1772) station. If someone is waiting behind you to use the DCFC station, and you need to charge all the way to 100% for some reason, you should move to a Level 2 station and let the next person absorb the full capability of the DCFC station. What is interesting is that this curve shows that this “Level 2″ threshold is not reached until about 93%, much higher than the 80-85% number that is often quoted as a charging etiquette guideline.

Tesla Model S DCFC charging power curve


I gathered this data in March 2015 on a long roadtrip in a Model S (thanks Keith R). There are two thresholds to note here.

First, similar to the i3 curve above, the Model S charges at max rate of 120 kW until around 35% SOC, and then starts to ramp down. Obviously the Tesla is charging far faster than the i3 to begin with, due to the far bigger car battery and far faster charging stations, but it still exhibits similar behavior — the battery can absorb full power only when somewhat empty.

Second, at around 65% SOC the car is absorbing around 60 kW. This is notable because it’s half of the 120 kW capability of the Tesla stations. Tesla supercharging stations are unique in the industry in that each DCFC cabinet (typically hidden behind a fence) actually supplies TWO charging pedestals (the plug hardware that you actually touch). If ONE car is plugged into one of that pedestal pair, it gets all the power. If TWO cars are plugged into each of the two pedestals associated with that one cabinet, then the cabinet splits the power between the two pedestals! I don’t know exactly how this split is done (equally? first person gets more?) but I suspect this 60 kW threshold may play a role.

Atlanta Tesla owner Keith R has made these observations:
– First one there always wins. And it also doesn’t even matter after you are above 65%. You will be capped to no more than 64 kW no matter what if your charge level is above 65%.
– Each DCFC cabinet has 10 modules (or 12). The first car “reserves” as many as it wants up to 7. That provides approximately 130-140 kW (~20 kW per module) and leaves 3 modules for a car arriving in the other stall. When the first car drops below 100 kW then it releases one of the modules, and again once it drops below 80 kW draw, etc. The second car enlists those released modules if it wants them. But it never “steals” from the first car that arrives. They only become usable by the second car if the first car isn’t using them.
– Whether another car is there or not doesn’t matter after 60% charge level (typically about 15 to 20 minutes) because that’s the point where the ramp-down curve crosses 64 kW.
– In the very worst case scenario, with two cars plugging in to shared stalls at almost the same time, both with nearly empty batteries – the “loser” will only have a 50% reduction for that 20 minutes or so… or to think of it another way, it can only cost you (at a maximum) an extra 10 to 15 minutes of charging time if you happen to get there last. And no loss if you get there first.

Nissan Leaf DCFC charging power curves

DCFC-power-LeafA couple owners in the Atlanta area helped me gather this data for the Nissan Leaf — thanks David K and Robert K!

The lowest curve is from a 2011 Leaf, showing how the battery technology in the earliest Leafs really not as good as just two years later.  Indeed, there is quite a bit of variance in the cars from year to year.

Most of these sessions were done on NRG EVGO stations, which as you can see peak out at around 42 kW. The one curve that peaks at around 48 kW is from a session done on a Blink DCFC station.