#### ajdelange

##### Well-Known Member

- First Name
- A. J.

- Joined
- Aug 1, 2019

- Messages
- 974

- Reaction score
- 455

- Location
- Virginia/Quebec

- First Name
- A. J.

- Vehicles
- Tesla X Extended Range Plus 2019, Lexus, Landcruiser, SR5

- Occupation
- EE Retired

It's amazing how much you can learn from a simple diagram like this one:

A charger has a maximum voltage it can deliver and a maximum current. Most have a power limitation which is less than the product of the maximum voltage and current. Such supplies use "limiting" to keep the supply within its power rating. As an operator increases the voltage setting the current will increase as will the power. When the power limit is reached the operator can no longer increase the voltage and thereby the current. BEV chargers are this type of supply.

There are 3 boxes on the graph above. One formed by the boundaries of the graph itself representing a power supply with 1500 V maximum voltage and 1000 A maximum current. The broken line box represents a supply capable of 920V and 500 A. This bounds the CharIn HPC150 to HPC350 class charger's power supplies. The curved lines represent combinations of voltage and current that represent a fixed power level. An HPC350 class charger has to be able to supply

The smaller dashed line box represents the voltage and current limits of a CharIn HPC50 class charger.

A vehicle's battery system is represented by a "load line" which is monotonic if not quite straight as shown on the graph. If the voltage is increased the current increases. The vehicle can control the duty cycle of the PWM in the charger's modules (it communincates this via a PWM signal but this is a separate PWM circuit reserved for communications). As one turns up this "volume control" he moves from left to right along the load line. The car continuously changes this volume control setting to match the charging profile it wants to implement.

There is tremendous flexibility in the system as currently implemented. There is a reason maximum voltage and current are not specified. And that is that fundamentally there are no limits using this approach. The present limit to CCS right now seems to be the connector which is limited to 1000V and 500A.

In designing a new car the manufacturer only has to insure that his vehicle's load line falls within the envelope of the chargers he wants it to be able to use.

Consider the Tesla or Rivian with their 385 volt battery packs. A hypothetical load line for a 385 V battery might look like the one labeled "Tesla" and extended by the dashed line "Rivian Lo". This load line intersects the HPC350 envelope at 500A and 400 V. The maximum power that these vehicles can get from an HPC350 class charger is 200 kW. This is less than the batteries can handle. So Tesla doesn't use an HP350 charger. It uses its own whose envelope's high current boundary is at 625 A and it is able to get 250 kW from such a charger but the current is a whopping 625A.

The Rivian battery can also take more that 200 kW but they want to use the CCS chargers and so split the battery into two halves and connect them in series. This makes the battery a 780 V battery with a load line like the one labeled "Rivian High" on the graph. This load line reaches the 300 kW power curve inside the HPC350 envelope. It is shown terminated on the 300 kW curve because that is the maximum that this battery pack can take but clearly could it take more it could run right up to the 350 kW envelope edge for this class of charger.

Now note that the 780V battery cannot charge from a HPC50 class charger because such a charger's maximum voltage is limited to 500 V. Switched to the Rivian Lo configuration, thouh, it can.

If some OEM decides he wants to build a car that can charge at 500 kW he knows that he will not be able to use any of the existing class of chargers but just as the existing classes have grown to HPC350 there is no reason there could not be an HPC500 class but it would have to have higher voltage capability (and probably need a new connector). There is no reason a manufacturer can't build a charger that exceeds HPC350 . But he will have to configure his battery pack (and connector bank) to be compatible with the existing classes if he wants to use them too.

A charger has a maximum voltage it can deliver and a maximum current. Most have a power limitation which is less than the product of the maximum voltage and current. Such supplies use "limiting" to keep the supply within its power rating. As an operator increases the voltage setting the current will increase as will the power. When the power limit is reached the operator can no longer increase the voltage and thereby the current. BEV chargers are this type of supply.

There are 3 boxes on the graph above. One formed by the boundaries of the graph itself representing a power supply with 1500 V maximum voltage and 1000 A maximum current. The broken line box represents a supply capable of 920V and 500 A. This bounds the CharIn HPC150 to HPC350 class charger's power supplies. The curved lines represent combinations of voltage and current that represent a fixed power level. An HPC350 class charger has to be able to supply

*at least*350 kW. It must, therefore, be able to supply any combination of voltage and current on the graph within the broken line box with the upper right corner cut off by the 350 kW power curve.The smaller dashed line box represents the voltage and current limits of a CharIn HPC50 class charger.

A vehicle's battery system is represented by a "load line" which is monotonic if not quite straight as shown on the graph. If the voltage is increased the current increases. The vehicle can control the duty cycle of the PWM in the charger's modules (it communincates this via a PWM signal but this is a separate PWM circuit reserved for communications). As one turns up this "volume control" he moves from left to right along the load line. The car continuously changes this volume control setting to match the charging profile it wants to implement.

There is tremendous flexibility in the system as currently implemented. There is a reason maximum voltage and current are not specified. And that is that fundamentally there are no limits using this approach. The present limit to CCS right now seems to be the connector which is limited to 1000V and 500A.

In designing a new car the manufacturer only has to insure that his vehicle's load line falls within the envelope of the chargers he wants it to be able to use.

Consider the Tesla or Rivian with their 385 volt battery packs. A hypothetical load line for a 385 V battery might look like the one labeled "Tesla" and extended by the dashed line "Rivian Lo". This load line intersects the HPC350 envelope at 500A and 400 V. The maximum power that these vehicles can get from an HPC350 class charger is 200 kW. This is less than the batteries can handle. So Tesla doesn't use an HP350 charger. It uses its own whose envelope's high current boundary is at 625 A and it is able to get 250 kW from such a charger but the current is a whopping 625A.

The Rivian battery can also take more that 200 kW but they want to use the CCS chargers and so split the battery into two halves and connect them in series. This makes the battery a 780 V battery with a load line like the one labeled "Rivian High" on the graph. This load line reaches the 300 kW power curve inside the HPC350 envelope. It is shown terminated on the 300 kW curve because that is the maximum that this battery pack can take but clearly could it take more it could run right up to the 350 kW envelope edge for this class of charger.

Now note that the 780V battery cannot charge from a HPC50 class charger because such a charger's maximum voltage is limited to 500 V. Switched to the Rivian Lo configuration, thouh, it can.

If some OEM decides he wants to build a car that can charge at 500 kW he knows that he will not be able to use any of the existing class of chargers but just as the existing classes have grown to HPC350 there is no reason there could not be an HPC500 class but it would have to have higher voltage capability (and probably need a new connector). There is no reason a manufacturer can't build a charger that exceeds HPC350 . But he will have to configure his battery pack (and connector bank) to be compatible with the existing classes if he wants to use them too.

Last edited: