Hi Paul, I have seen exactly the same symptoms. The batteries were emptied in about 2 weeks, and some unexpected log files appeared on the SD card. They contain only about 6000 data points, so I doubt the logging alone can account for the battery drain. The logs are irregular, stopping and starting at unexpected times.
I’m sure James will sort it out. For now I have withdrawn from the beta-test programme and re-flashed the stable firmware, and the Mooshimeter is working nicely again.