What is a second life Battery?
The electric vehicle battery or the “traction battery” is no longer useful after twelve to fifteen years of usage. As the traction battery is tortured while used in a vehicle due to fast charge and discharge currents in different temperature conditions the battery gets degraded.
Now after ten to fifteen years of usage the batteries are not capable to deliver the performance that they used to deliver when they were new. Now the end user needs to replace its batteries with the new one.
The batteries which are removed from the automobile has eighty percentage of its capacity still left in it, Now it can be further used before getting recycled. Now this battery is called as a Second life battery when it is used in other applications or repurposed for “second life” after being used in Automobile.
Certification of Second Life batteries
EV batteries that are repurposed goes through three step process
- Assessment: The battery engineer’s examine the batteries coming out of an EV whether they can be further used or not by knowing the history of the manufacturer and the end user.
- Remanufacturing: The batteries can be used directly as it is in some cases, but sometimes needs to be remanufactured depending on the application it will be used.
- Recertification: Finally, the battery manufactured needs a certification depending on the intended use. This includes regulation for transportation such as UN 38.3 and electrical safety regulations and standards.
It is very important to follow established standards and guidelines, such as the UL 1974 is a standard for assessments of repurposed batteries. UL 1974 includes requirements that the battery must pass the tests regarding safety and performance.
If not UL 1974, The batteries must be judged to applicable safety standard from IEC, NFPA, ANSI or other industry organizations.
Application of Second life batteries:
- Telecom and datacenter backup services: Currently the largest second-life application in the world, as the application needs stable power supply.
- Behind-the-metre storage services (BTM) : Residential or commercial application, used to provide back up power when there is a power cut. Most of the Homes are behind the metre, which means the electricity must come through the metre.
- Front-of-the-metre storage Services (FTM): Utility scale services that targets applications for frequency regulation, voltage support and excess renewable energy storage.
- Low power electric vehicle: Since the batteries cannot power the passenger vehicles though it can be used to power slow moving vehicles like Golf carts, fork lifts etc.
Challenges while using second life batteries:
- Requires track and trace of each battery cells/module because knowing the history of each battery is important to decide whether its suitable to use in second life applications and even after second life application when it goes for the recycling process during the end of life when its no longer able to hold charge.
- BMS needs to be changed depending on the application, we cannot use the same BMS in the Grid storage application which was used in EV.
- EV Battery cells comes with different chemistries, form factor, modules cannot be mixed up while using it in second life application, It requires sorting of batteries depending on the chemistries, capacities ,and form factors.
- Batteries must be certified if used in a grid storage types of applications, where safety cannot be compromised.
- Lithium ion batteries are classified as class nine hazardous materials, transportation and handling of these batteries are a big challenge.