A mathematical model for an anodic half-cell redox-flow lithium -ion battery is derived and complemented with experiments. In short, the model considers conservation of charge and species - two redox shuttle molecules and their ionic counterparts - coupled with electrochemical reactions in the battery and conservation of species coupled with chemical reactions in the tank. Based on quantitative arguments, it is postulated that such a model is sufficient to capture the behavior of the system. This is confirmed by calibrating and validating the model with a training and test set from the experiments respectively overall, good agreement is found. In particular, the model is able to capture the two distinct charge and discharge regimes that occur in the system as well as the dependence of the overall battery performance on the chemical reactions taking place in the tank. (C) 2016 Elsevier Ltd. All rights reserved.