[brian_]

Does anyone know how 500V DC charging stations behave if a car plugs in and requests, say 550V terminal voltage?

Will the station charge the car to a maximum of 500V, or will it not charge at all?

I don't know, but the voltage choice is a bizarre boundary case. A car needing over 500 V is probably way over 500 V - like 720 V nominal - so even the fully discharged voltage is probably over 500 V and no charging can occur at all.

Are you considering a pack around 500 V nominal, so a 500 V max charging station could take the pack from fully discharged to roughly half-charged, if it interprets a 550 V request that way?

 

[lochnessnomster]

I don't know, but the voltage choice is a bizarre boundary case. A car needing over 500 V is probably way over 500 V - like 720 V nominal - so even the fully discharged voltage is probably over 500 V and no charging can occur at all.

Are you considering a pack around 500 V nominal, so a 500 V max charging station could take the pack from fully discharged to roughly half-charged, if it interprets a 550 V request that way?

Thanks Brian. 550V was plucked out of the air. I'm considering a pack with around 510-520V terminal voltage, expecting to be able to charge to 75/80% on older DC chargers. The OBC will support 500+V for 100% charge.

The idea is you don't generally charge much past this on DC anyway and this design has higher nominal voltage for improved capacity, efficiency and higher charge/discharge power (for the same current).

Most newly installed chargers appear to provide 150-920VDC, even those that are power-limited to 50kW so it would be a non-issue on those.

I am curious how the CCS2 protocol behaves if the car requests higher terminal voltage than the supply. Whether it will charge with requested current until 500V and then taper, or whether it will refuse the vehicle for incompatibility..?

EDIT - 0% voltage of around 430V.

 

[brian_]

That makes sense.

If the CCS protocol or actual implementations are not cooperative, perhaps a workaround (requiring some work on the car side) would be to request only 500 V when the charger is known to be limited to that, knowing that it will not result in a full charge but ensuring compatibility?

 

[lochnessnomster]

That makes sense.

If the CCS protocol or actual implementations are not cooperative, perhaps a workaround (requiring some work on the car side) would be to request only 500 V when the charger is known to be limited to that, knowing that it will not result in a full charge but ensuring compatibility?

I have a feeling this is going to be a case of 'try-and-see' and then eject a module or two if it's not workable!

 

[remy_martian]

The car pulls current, not voltage and the car manages its own pack voltage; the charger could care less within its operating limits...

There's no magic. Above 500V you get zero current.

There should be protection circuits in the charger that keep you from backflowing current from a higher voltage pack. Should be...it might cost you 50 grand to find out.

In other words, if it's a 500V charger, you aren't getting 501V from it and don't even think about charging the charger 😂

You'll have no choice but to charge Level 2 (high current 240VAC, assuming you're in NA) and use an onboard charger if you want more than 500V for your pack voltage....unless you can find a very rare 800V charger and your stuff is rated for it (even your wire changes).

 

[lochnessnomster]

The car pulls current, not voltage and the car manages its own pack voltage; the charger could care less within its operating limits...

There's no magic. Above 500V you get zero current.

There should be protection circuits in the charger that keep you from backflowing current from a higher voltage pack. Should be...it might cost you 50 grand to find out.

In other words, if it's a 500V charger, you aren't getting 501V from it and don't even think about charging the charger 😂

You'll have no choice but to charge Level 2 (high current 240VAC, assuming you're in NA) and use an onboard charger if you want more than 500V for your pack voltage....unless you can find a very rare 800V charger and your stuff is rated for it (even your wire changes).

I understand the car draws current and that current will taper as we approach 500V. My question is more about the charging standard rather than battery chemistry.

As I understand it, the CCS protocol involves an exchange of max voltage and max current information for both the EVSE and EV before charging begins. What I don't know is whether the EVSE will reject the car, or deliver power up to its max operating voltage.

Majority of new installations in the UK are rated 150-920VDC so will have no problems with those.

 

[remy_martian]

As far as I know, the car only asks for current and its BMS monitors pack voltage