Second-life batteries for self-consumption

Research coordinated by Université de Haute-Alsace

Lithium-ion batteries are widely used in electric vehicles. However, it is no longer possible to use them for mobility when their performance decreases.We propose to study the reuse of batteries from electric vehicles for a second life in stationary storage. Modelling will be carried out to qualify the batteries and gain a better understanding of their state of health (SOH). Active cell balancing will be proposed to increase storage life for self-consumption.

Particular attention will be paid to accurately determining the state of charge (SOC) of batteries using intelligent algorithms and state of health (SOH) estimation.
Simulation tests and case studies will help determine whether it is more appropriate to reuse end-of-life batteries in stationary storage, or to recycle the materials. Best practices based on used battery scenarios from the three countries will be proposed for intelligent self-consumption. The aim will be to highlight the advantages and disadvantages of reusing second life batteries, and propose models for making the most of the ecological, technological and economic benefits.
It is important to balance the charges of the cells inside used batteries to increase their lifespan. To give used batteries the longest possible second life, it’s important to actively balance the different cells. Healthy cells help weaker ones.
As an extension of active cell balancing, this task will develop concepts for dynamically reconfiguring the series and parallel connection of cells or groups of cells to dynamically distribute charge and power, to adapt the battery terminal voltage and even to isolate and bypass faulty cells.

The results of the studies and the solutions proposed above will be tested, both in simulation and in real-life situations in the three countries. The project’s partner companies will be involved in selecting scenarios that can be directly transposed into real-life situations, considering societal surveys of user acceptability.

The following actions are expected:

State-of-the-art report on the reuse of second-life batteries in static storage.
Workshops involving automotive, battery and self-consumption manufacturers on second-life batteries.
Detailed report on the precise identification of SOH (state of health) and SOC (state of charge) battery indicators. Deep learning neural networks such as LSTM (Long Short-Term Memory) will be used to increase measurement accuracy.
Report on the improvement of active cell balancing solutions to improve battery life in stationary use.
Analysis of ideal block sizes in terms of costs and benefits, hardware demonstrator, publication of results in international journals.
A report on best practices for intelligent self-consumption based on used batteries.
Tests will be carried out on pilots such as the electrical microgrid available at UHA, equipped with 9 kWp photovoltaic production and 30 kWh lithium-ion battery storage. Scenarios from the three countries can be tested with different loads, including electric vehicles.
Best practices will be proposed, with technical solutions for intelligent self-consumption coupled with storage derived from recycling.

This WP interacts with all other WPs.

Taking into account the societal studies carried out in WP3, WP4 and WP5 to integrate users’ perceptions and expectations for better recycling of used batteries.
Consideration of the legal framework developed in WP6 to fine-tune self-consumption solutions.
Consideration of the estimation of SOH (state of health) and SOC (state of charge) battery indicators in WP7 for the online Vehicle-To-Home design tool.
Strong interrelations are expected with other technical Work Packages to improve intelligent self-consumption.

An algorithmic innovation is planned to improve the real-time implementation of intelligent solutions.

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