*3.7. Serviceable*

The last failure mode listed is labelled *Serviceable*, which defines actually still good, functional batteries whose ageing progress has not yet led to failure. These batteries were replaced prematurely, presumably due to customer request. This failure mode is therefore not a failure mode of the battery but only indicates how many batteries have been replaced before the end of their lifetime.

These five major failure modes presented in the previous sections can be found in the field data in Figure 2 and in Section 3.1. The following Section 4 presents the results of the Weibull analysis and the calculated time-dependet failure rates *λ*(*t*).
