A battery system monitor includes cell measurement circuits (CMCs) that each measure a voltage at or current through a pair of terminals of a respective associated battery module from among a plurality of plurality of battery modules in a battery system. Wireless communication transceivers (WCTs), each associated with a different CMC, transmit voltage or current measurement information of the associated CMC across a wireless communication link. A controller receives the voltage or current measurement information from the wireless communication transceivers for monitoring the state of operation of the battery system. Battery system monitoring is improved through synchronization of clocks in different CMCs or WCTs to enable synchronous sampling of multiple battery modules, through systems for determining relative positions of battery modules in a series coupling of battery modules between terminals of the battery system, and through improvements to the reliability of wireless communication.