The results of an in situ investigation of the structural changes that occur during the operation of working battery electrodes using synchrotron radiation are presented. Two types of electrodes were investigated: an AB2-type Laves phase alloy anode with the composition ZrxTi1-xM2 and a proprietary cell based on a LixMn2O4 spinel compound cathode made by Gould electronics. For the Laves phase alloy compositions with x=0.25 and 0.5 and M=V0.5N1.1Mn0.2Fe0.2 were examined. Cells made from two different batches of LixMn2O4 material were investigated. The relationships between battery performance and structural changes will be discussed. In the later case, we also discuss the role of over-discharging on the LixMn2O4 structure and on battery operation.