As promised, more tests were done, and more are to follow.
One test consisted of taking the battery on longer daysail (see the thread "
Genre:party cruise" for the type of outing). It involves crossing several connected bodies of water, including those that I already tested the motor in. The problem this time of year is that the winds can be fickle, and also have a tendency to "lift off the water", especially for the return, leaving some bays and cuts with mirror smooth water. My previous setup with two 80Ah batteries and trolling motor, did not always have enough range to get me back; to get under bridges the motor is needed on the outbound leg and that can make things tight if the winds don't get me across at least half my return distance.
This year was no exception from the general pattern, in fact, on the chosen day the wind forecast was the weakest. One thing that made a difference was that the battery is so light and charges so fast, that I could take it with me on the other end and plug it in while I attended the party and start my return with a fully charged battery.
We saw some decent wind on the lake when decided to start our return, but with some inevitable delay ended up hitting the water just when the wind died. We motored out into the main lake where we picked up inconsistent zephyrs that allowed ghosting but no progress. We enjoyed the full moon a bit and then spied a promising wind patch and motored to it. Got a nice steady breeze to get us across the bulk of the lake and through half of one of the bays. But under the bridges and some of the smaller bays we had to motor.
The battery is rated for 60min at full power; we did 48min and then another almost 30 mins at half power (which is a bit slower, but much faster than 1/2 speed, perhaps 3/4). That got us home. As full speed with the test motor is a bit faster than with my trolling motor, we can round this result to say that we could have motored for 80 mins with the same speed as with the trolling motor, something that would have put both of the deep cycle batter down to half charge. That from a single 6.4lb battery.