A calorimetric method is based on the cell heat-generationstudy. According to Forgez et al. [8], there are four heat sources ina battery: electrical losses, entropic heat, heat generated by sidereaction(s) and heat of mixing. Concerning the studied battery, sidereactions are mostly aging reactions that are slow enough for theirheat generation to be neglected. The heat of mixing is negativeduring the creation of concentration gradients and is positive whenthese gradients disappear (the sum being zero)