Control of Lithium-Ion Battery Warm-up from Sub-zero Temperatures

Abstract

The archetype of rechargeable technology, Lithium-ion batteries have over the last decade benefited from improvements in material science through increased energy and power density. Although widely adopted, these batteries suffer from significant performance degradation at low temperatures, posing a challenge for automotive applications, especially during vehicle start-up.

One way to counter the impact of cold weather conditions is to warm the battery. This begs the question: can we derive a good warm-up strategy? How would it look? Moreover, if as much as 22% of the reduction in the range of electric vehicles is attributable to onboard battery heating systems, would an energy-optimal heating strategy alleviate this range-drain? At what expense?
This thesis answers these questions by addressing the four main aspects of control design: modeling, control, verification and adaptation. Two energy-optimal warm-up strategies are posed and associated tools — that enable prudent decision making on whether warm-up is feasible — are developed.

The methods developed are demonstrated via a combination of simulation and experiments on Iron Phosphate or Nickel Manganese Cobalt Li-ion battery cells which have high power capability and could be used in replacement of 12V starter batteries or 48V start-stop applications.