EV Batteries Have a Brief Maximum Charging Rate

by | Mar 2, 2023 | About

Understanding how energy storage supports EV charging sites requires a mixture of knowledge in both upstream grid functionality and downstream EV battery demands.

Sparkion’s technology simultaneously matches energy storage support with the needs of the exact site at a specific time. To achieve this, it’s vital to leverage Open Charge Point Interface (OCPI) data from the chargers, which are getting a live feed from the vehicle, in order to understand what capacity to charge at.

Every EV model has a unique onboard battery management system (BMS), which leads to a specific charging pattern. One key component of the BMS is to control the temperature ranges of the batteries, which helps to optimize performance and cell life. Through the vehicle’s telematics system, the BMS data, such as state of charge (SOC) of the battery (i.e. 0%-100%), is communicated to the ecosystem to optimize how energy flows to the vehicles. It’s important to note that lithium batteries start to charge at a slower rate as they approach 100% SOC.

For example: A Tesla Model 3 Long Range charges at 192kW when it only has 10% of range, but once the battery is charged to 30% it drops all the way to 130kW. Then, once the vehicle is at 50% SOC it’s charging all the way down at 88.5kW. Once the Model 3 reaches 80% SOC it’s down to 45kW. Now, it’s vital to consider the time at which the Model 3 is actually charging at high power – between 192kW and 130kW (10%-30%). In total, it’s around seven minutes of charging, during which only four minutes are using over 150kW.

This is crucial when considering how energy storage can protect against a site’s peak kW usage, and more importantly, how many kWh of stored energy are needed to do so, based on the amount of time needed for the protection. In the case of the Tesla, even if two Teslas arrive at 10% SOC at exactly the same time, Sparkion’s ESS would only need to provide four minutes of energy to ensure the site’s demand charge doesn’t go above 150kW, and seven minutes to keep the demand charge below a multiple of 130kW. When looking at it from this viewpoint, an ESS can make a huge impact just by protecting a site’s max kW for a small period of time.

EV Batteries Have a Brief Maximum Charging Rate