Here's what I have found related answer for your question.

I am not sure, I have not run out of battery power after sailing the boat for 4-1/2 hours in medium wind, using a NiMH 1200 ma, 6v rechargeable battery pack in the boat. The batteries will provide less time in very windy conditions--and more in light wind. The transmitter has NiMH 2500 ma AA batteries,and draws about 300ma. They should last about 8 hours. The transmitter time has been verified by one of our skippers who erroneously failed to charge the transmitter batteries after two extended sailing adventures. They died on the third sail. I have heard that alkaline batteries last about 6 hours in the receiver.