The Geode Seismograph uses 0.5 W/ch during acquisiton with a 0.25 ms sample rate. With that power consumption, a single 12 amp-hour battery is sufficient for a typical day of data acquisition.
In standby mode, power consumption is reduced by 70%. We recommend you run each Geode AU unit off of its own battery (2 is one and 1 is none), but you can run two Geode's off of one battery if the battery is able to deliver 2 amps per hour.
The smaller the battery, the more often it needs to be recharged, so keep that in mind when deciding on your power source.