Batteries for electric vehicles are, in general, monolithic blocks accommodating individual cells and the necessary technology. While all cells should, in theory, be able to save the same amount of energy, this is not the case in practice. The team says this is problematic; since cells are connected in series, the battery is only as strong as its weakest cell. If this cell is ‘empty’, the energy in the other battery cells does not help and when a cell is defective, the vehicle stops functioning.
Researchers at the Fraunhofer Institute for Manufacturing Engineering and Automation IPA have created an alternative. “Our modular battery system solves these problems,” claimed Dr Kai Pfeiffer, group manager. The solutions sees each battery cell equipped with a microcontroller that records relevant physical parameters, such as temperature and the cell’s state of charge. As a result, each cell knows what condition it is in. The cells can ‘talk’ to each other via the existing power wiring between battery cells. An on-board computer uses data from the cells to calculate how much remaining energy the entire battery still has.
If a cell is empty, but others have energy stored, the empty battery cell can be decoupled from the cluster, allowing the others to continue to deliver energy. “Depending on the cell quality, we can therefore increase the range by at least 4%,” explained Dr Pfeiffer. “Over time, this effect is amplified: in the case of an old battery, and if the empty cells are replaced, it is conceivable that a range up to 10% higher can be achieved.”
Since one cell with lower capacity hardly affects the overall range of a car, manufacturers no longer need to pre sort them, reducing costs.
While the researchers have developed a prototype of the battery cell, their next challenge is to miniaturise the electronics and embed them into cells. “We want it to cost less than €1,” Dr Pfeiffer noted.
