On board AC chargers compared to off board DC chargers

On board AC chargers compared to off board DC chargers

200 mile EVs are coming. Will we be ready to charge? First of all, home is already the primary place for charging. With 150-200 miles of range, the number of times we charge outside our home/work will be reduced even more. This new found range may however change our outlook on charging. First, a statement  on AC charging. Until now, most of our charging has been AC largely due to convenience of available AC and the ability to agree on a common connector, the J1772, but that may be about to change.

How could  DC charging be the future for EVs? Short and simple… speed. Speed-to-cost ratio to be more specific.  The SAE Charging Configurations and Ratings Terminology graph above provides the following for 25 kWh BEV comparison for on board AC chargers vs off board DC chargers:

Level 1 1.4 kW 12A AC charger =17 hours compared to up to 36 kW 80A DC charger = 1.2 hours.

Level 2 7.2 kW 40A AC charger =7 hours compared to up to 90 kW 200A DC charger = 80% charge 20 min.

Until now, the industry has also chosen to build the charger into the EV, or on board, with the electric vehicle supply equipment (EVSE), serving as a safe method of connecting to the EV. The concept of using an off board charger is slowly manifesting in Asian and European markets.  Our own IEVs European correspondent Mark Kane previously reported on Denza DC Wallbox development found here.  Mark reports a Denza 10kW wallbox for $1600 or a 20kW for $3200. Compare that to an EVSE that can be purchased  for $500-$800 and at first glance most would  opt for the cheaper EVSE option.

That is until you realize that you could get by with a less expensive low power on board charger for ALL of your future EVs. If you have made the switch to EVs, you do not need to keep buying the high power on board charger, thus saving you money in the long run--assuming the infrastructure is there to support it. With 200 mile BEVs on the way, does this change the way we look at the long term investment of maybe a $1000-$2000 premium for a home DC charger?

Denza DC charging

Denza DC charging

DC Direct for home charging

Recently Tesla Motors announced that they would be introducing a home storage battery to help with the indeterminacy of solar and wind as well as functioning as emergency backup power. For those who purchase this DC storage, they most likely have a DC source of power in wind and solar, and if they own an EV, they now have closed the loop in their DC system no longer dependent on AC conversion. DC solar > to an AC inverter > then back to DC storage is the current model. Currently PV-EV users are losing upwards of 16% in conversions. Of all the questions asked about the upcoming Model III, the most intriguing may be to see if Tesla Motors will offer/market a complete DC direct package? Musk has stated that the home storage will be "plug and play." Presumably they will integrate to their on board chargers, gaining  efficiency through a DC direct package. Though this model will not be limited to Tesla, they may be the first auto manufacturer to offer the package.

This model will in the future be expanded to vehicle-to-home (V2H) .  V2H systems will connect through Home Energy Management Systems (HEMS) integrating roof top photovoltaic solar panels and will communicate the optimal charge and discharge patterns.

DC Public Charging

DC QC standards

DC QC standards

As for public chargers, would it not be desirable to simplify your EV's on board charger? Could mid-range (20 kW)  fast DC chargers nudge out Level 2 EVSEs, thus allowing EVs the option of passing on high power on board chargers with every purchase? This scenario is more likely to play out on low end EVs while premium models hold on to high power on board chargers. Some form of low power on board charger is a must due to the convenience and accessibility to an AC plug.

How does DC affect commercial deployment? It comes down to the speed-to-cost ratio. Labor cost is the largest expense for commercial deployment. The difference in material cost vs the speed of public charging very well could push mid-range DC charging (think 20 kW)  forward to properly fill that which has been currently attempted by Level 2 EVSEs combined with supported on board chargers.  20 kW requirement would be more readily available in some urban and commercial setting.  Bill Howland comments that 80 amp 208 volt 3 phase or 35 amp 480 volt would be economical so feeders to existing electrical panels are minuscule, provided only 1 or 2 fast chargers per location.  This approach is not aimed at long distance highway travel, but does the introduction of the 200 mile BEV change the needs at hotels, airports and other 150+ mile destinations as well as the mall, library, and other public parking usage of the current Level 2 EVSE?

20 kW DC fast charging will never replace the need for long distance highway travel. The speed provided by the power of  50 kW - 100 kW DC charging does however increase the expense ten fold in deployment. So far, Tesla Motors, a single start-up manufacturer has tackled this issue for their customers with the deployment of their own  supercharger network. If a start-up producing 30,000 autos per year can deploy a functional 120 kW network in Asia-Pacific, Europe, and North America over three years, then surely there can be a solvable deployment. In a way, it has been somewhat of a hidden blessing that this has not happened yet as both rapidly changing power requirements, along-side of determining standards has limited expansion as much as the cost. Fortunately, other auto manufacturers have stepped up there commitment to supporting highway quick charging. Recently BMW and VW have teamed to provide electric  bridges across  North America.

Standards

Tesla CHAdeMO Adapter - Despite The -Coming Soon- Status, We Can Now Confirm That Tesla Is Shipping These Adapters

Tesla CHAdeMO Adapter - Despite The -Coming Soon- Status, We Can Now Confirm That Tesla Is Shipping These Adapters

A continued issue facing any type of DC deployment is standards. For the near future, it looks like many will be purchasing at least one DC adapter in the life of their EV. This is an item you most likely will hold on to between trades. Recently Tesla released information on their CHAdeMO adapter for their customers. Currently CHAdeMO is the closest thing to a standard in the US, thus what you are most likely to currently find in a public DC fast charger. Expect future deployment of SAE Combo chargers, thus driving a need for the alternate adapter in the future. With the arrival of many 200 mile BEVs supporting the SAE Combo standard, it is not too soon to start asking about a CHAdeMO adapter.

The other solution is to provide dual CCS and CHAdeMO connectors as BMW and VW have agreed to do in their bold quick charge commitment.  Would it not be great if Nissan chooses to do the same?

200 mile BEVs are coming. How will we support them and how will your charging patterns change? How would mid-range 20 kW fast DC charging affect your future usage by tripling the speed of current Level 2 EVSE charging? Would you be willing to pay a small premium for the ability to use a mid-range fast DC charger in the current/future Level 2 locations to cover deployment costs? How soon must we deploy 100 kW  quick charging DC infrastructure and do we know what to deploy?

While waiting on these high level decisions, there is going to be a lot of trouble free miles when leaving the home with a topped off 80% (160 mile) charge every day.

Leave us your thoughts.