Can we use 250KW charger to charge a 20KW EV battery Vehicle ?

Yes, We can generally use a 250kW charger for a 20kW EV battery, but with some important thing need to remember :

Key Considerations

• Battery Management System (BMS): The car's BMS is crucial. It communicates with the charger to regulate the charging process. It will ensure that the battery receives the appropriate voltage and current, preventing damage from overcharging or excessive heat.

• Charging Rate Limit: Every EV battery has a maximum charging rate it can safely handle. Even if you plug into a 250kW charger, the BMS will limit the charging rate to the battery's maximum capacity. With a 20kW battery, the maximum charge rate will likely be significantly lower than 250kW.

• Charging Pattern: EV batteries don't charge at a constant rate. They typically charge faster initially and then gradually slow down as they approach full capacity. This is known as the charging curve. The BMS manages this process to optimize charging speed and battery health. 

What to Expect: 

• Faster Initial Charging: You might experience a faster initial charging rate compared to using a lower-powered charger, but this will quickly taper off as the battery gets closer to full.

• No Damage to the Battery: If your EV and its BMS are functioning correctly, using a higher-powered charger will not damage the battery. The BMS will act as a protector.

• Not Necessarily the Fastest Charge: While you can use a 250kW charger, it doesn't mean your 20kW battery will charge incredibly fast. The limiting factor is the battery's capacity and its maximum charging rate.

Example:

Take the case of the TATA Nexon Vehicle, The battery pack is 320V & 90AH Capacity, Energy is 28.8KWh.

The maximum energy the Nexon battery accepts for charging depends upon the BMS inside the battery pack and the nominal charging ampere of a 90AH battery is 45Amps, 

The 55KW charger can charge the 28.8KW Pack of Nexon Car with a maximum of 16.4KW , 

How. Since the Lithium cell's maximum voltage is 3.65v and we multiply 3.65*100 Cells is 365v. then multiply 365v*45A (Nominal Charging Current ) which is 16.4KW.

Note:

There are different types of chargers available,

1. Slow Chargers.

2. Fast Chargers.

3. Ultra Fast Chargers or rapid chargers.

To learn more about the types of chargers, click the below post...

The charging speed and time depend on the power supplied by each type of charger and also depend on the capacity of the battery.

In Summary

Using a 250kW charger with a 20kW EV battery is generally safe, thanks to the BMS. However, don't expect a dramatically faster charging time compared to a lower-powered charger. The battery's limitations will determine the actual charging speed.