NACS - Charging below 200v?

[Username1]

The Tesla connector is now the standard for North America, which included adopting the non-proprietary CCS communication protocol. To cut to the chase, I’m wondering if it’s possible (in theory) to DC charge our PEVs...

I commonly see “200v” discussed as the lower limit for CCS charging. Some say it’s a limit of individual charger hardware, with others saying it’s a limit of the communication protocol itself. After lots of digging, I can’t seem to find a straight answer.

Tesla V3 superchargers state an output of 0-500v on the sticker. So I’m wondering if it’s possible to use CCS communication protocol to directly charge below 200v without the use of transformers. Why or why not?

By the way, I’m not even trying to attempt this myself. I just want to know if it’s possible. For example if PEV manufactures could include this capability in the future, especially once super high power cells come to market.

 

[Pajda]

In short: It's possible, but it's not practical.

The practical reason is the same as for moving from 400V to 800V systems, at low voltage you won't transfer decent power at a reasonable current. Basically, the CHAdeMO standard came up with a similar idea to support LEVs, and has the mandatory support for 50-500 Vdc output range. If I'm going to complain about CHAdeMO (this standard has brought nothing but pain to the world) I don't know how anyone could think it would be useful to transmit such ridiculous power as 6.25 kW (50 V @ 125 A) in such an expensive way.

But this issue can still be seen even in modern production, for example BMW iX1 and iX2 (78s NMC pack) or new Hyundai Inster (74s NMC pack). Both vehicles require 500 A to achieve the promised charging power of 120 kW. Which means that at regular 50 kW @ 125 A DCFC will both vehicles charge a pathetic 30-36 kW.

So the only practical way how to support LEV charging on conventional DCFCs is to use the same principle of a switching the vehicle battery connection from 100 Vnom (which is common for LEVs like motorcycles) to 200 V for DCFC charging purposes only, e.g. similar to how Tesla and VW are now doing it on their new platforms.

 

[Souvlucky]

CCS2 DCFC stations voltage DC output range often starts at 150VDC nowadays.
It used to be more common to see a 200VDC min.

Some points to consider:

1. In DC fast charging, the station outputs what the vehicle's charging controller requests – not a fixed open-voltage output, so if the battery is at a station of charge lower than the station minimum DC voltage output, charging won't work;
2. Not all DC charging stations today are recent and many deployed on the field have an min. voltage output of 200VDC "only" (previous generations);
3. Except if having visited it or knowing the charger models used by specific charge point operators, it's often difficult to know in advance if a specific DC station has a minimum voltage output of 200VDC or 150VDC.
4. (If we presume that the choice is not to add a DC/DC step-down converter in the system – though technically possible and very interesting idea to engage with!);
5. If we aim for a battery that is compatible with the widest available network, meaning a 200VDC minimum lower cut-off range...

Then the battery configuration (supposing today's NMC/NCA cathodes and common electrolytes) would have to be:

• Minimum 67S, accomodating a 2.50V cell low voltage cut-off, or;
• Minimum 80S, accomodating a 3.00V cell low voltage cut-off.

DCFC handshake and duty control from the vehicle side is also not exactly trivial.
On that, great work being done here (the FOCCI project) by members of the openinverter community!