MarkSetBot offers two battery options, a 50ah and 100ah lithium-ion battery. In normal conditions (i.e. 7-10 knots of breeze, 1-2 foot waves), the Bot has an approximate battery life of 12 hours with the 50ah battery and 24 with the 100ah. This battery life, however, fluctuates depending on how much the Bot must move around (course changes, motoring to course), wind speed, waves, and current.
In our trials, Bots have been able to last 8-10 hours in windy (over 20 knot) conditions even with the 50ah battery. The 100ah only extends this capacity. So, regardless of the battery option, and holding all else constant (current of 0), in wind-speeds of 20+ knots, the Bots can easily make it through an entire day of racing.
When you send a bot out to the race course on it's own, it uses more battery than when holding place. Sending a bot 1nm uses about 10Ah (20Ah round trip). That leaves you with 30Ah or 80Ah depending on the battery you select.