My application idea for the TAPAS board is about batteries, especially used Li-Ion cells, with many cycles on them. The TAPAS board will be part of a fully automated test system to analyses the performance characteristics of the Li-Ion cells. Knowing these characteristics, which are different compared to a new cell, is important to evaluate the possible second-life use cases of older batteries. The Raspberry Pi will monitor and control the test system and host a digital platform to analyse the data.
The main performance characteristics are the internal resistance. the capacity and the self-discharge of the cell. The capacity can be measured during charge and discharge cycles. Discharging at different C-Ratings (1-10C) can give a realistic results on the real capacity for different load situations.
The internal resistance can be determined using different methods. However the internal resistance also depends on the method used and thus several methods will be implemented using the TAPAS board - the current step method and more important electrochemical impedance spectroscopy (EIS). The fast switching possible with the TAPAS board is perfect to implement EIS as i needs a signal in the kilohertz range.
The self discharge will be monitored while the cells are waiting to be tested as well as afterwards
A system made with the TAPAS boards could control the charging and discharging very accurately up to the high frequencies of several hundred kilohertz need for the EIS
In addition to the TAPAS boards, a data acquisition board based on a 24bit ADC (TI ADS1248) called TeensyDAQ , which is currently being test, is part of the system. Its function is to supervise the cells temperature and measure very accurately the voltage during the tests. More about this project: https://hackaday.io/project/158060-teensydaq
An overview schematic of the automatic test system is shown in the attached picture. The use two TAPAS boards would reduce the testing time and allow for different test setups at the same time. The Li-Ion cells, 3 at the same time, are loaded on to a carrier which is loaded into a hopper. A linear motions system transports the carrier with the cells from the input hopper to the first TAPAS board, then to the next and places it into the output hopper.
This first test system would also help to evaluated the business case of reusing li-ion batteries by generating first real-world test data and and estimating the effort that would be needed for large scale battery testing.
this idea gets two TAPAS dev kits