Battery Life eXTension
Battery Life Extension, is a tool that DNV GL has developed based on extensive testing databases to size, predict degradation, and virtually test battery packs. DNV GL is presently using modeling to extend the operational limits of batteries, and validate the life extension and safe operation of batteries in a variety of applications. There are presently two main initiatives in the project, both of which are in collaboration with external partners and funding organizations:
In the US, DNV GL has partnered with companies to examine the deployment of a novel gas sensor that detects battery off gas. This will first be demonstrated on new batteries, and the lessons learned will be applied to second-hand batteries to demonstrate the viability of a “second life” of batteries. The life extension limits and model parameters will be validated along with the sensor in the deployment and demonstration in a Community Energy Storage (CES) platform. The underlying hypothesis of the project is that two factors limit the performance and revenue potential of battery-based energy systems: first, conservative estimation of the SOC limits and C-rates minimizes potential stresses on the battery but inhibits its maximum performance; second, retirement of batteries under the assumption that their remaining capacity has no value is premature. The project aims to use battery life prediction modeling and sensor monitoring to identify scenarios where the limits of battery operation can be pushed so as to extract greater performance without adversely affecting the net lifetime throughput. The sensor validates these limits and the model predicts performance with the newly established limits. It is presumed that sensor signals will provide early warning of battery stress prior to failure conditions, such that the performance envelope can be more accurately measured. In addition the project will demonstrate the implementation of second-hand batteries into a CES system to validate the remaining capacity of batteries and test their viability using the modeling and sensor approach.
In Europe, DNV GL is partnered with a mobility company to examine the use of batteries in second-hand applications, as well as new mobility markets such as hybrid ships. Projects in these areas span issues associated with rural electrification of transportation, implementing high power and high energy density batteries in ships such as tugboats and ferries, as well as using second-hand batteries to enable affordable microgrids.
The viability of second-hand batteries is greatly dependent on their intended application and the prior stresses that the batteries have experienced. DNV GL has found that if a battery is to double its revenue over its lifetime, it may be possible to pair the battery with applications where high revenue is earned for its energy throughput with only a 20-30% of its service life. This hypothesis is being tested with the programs described above.
The BXT program ties into existing DNV GL KEMA activities related to energy storage and compliments qualification and validation of battery-based energy storage systems.