The state of health (SOH for "State of Health") of the lithium battery that powers any electrical device is a legitimate concern, because it has the defect of degrading, a little over time, but above all with the use we make of it, and thus lose storage capacity and power. Its knowledge even becomes crucial when it comes to an electric vehicle since its autonomy and its price in the event of resale are at stake.
However, car manufacturers have so far been reluctant to easily provide this information to their customers. It is necessary to deepen the subject, much more complex than it seems, to understand why and to know if we can really know the state of health of a lithium battery, and if so under what conditions.