Simon, with all Dave Maynard’s electronics in the boat I’m surprised you did not need a generator!
Although a battery in the boat gives you a decent power source it’s yet another piece of gear in the boat.
Just wondering if you checked for any compass deviation?
How close was the battery to the compass?
There’s a nice story in one of Pat Dollard’s logs coming back across the channel. After a long downwind sail, when they closed the coast they found themselves several miles off course. The culprit was found to be a steel stove stowed in the different position that had given a few degrees of deviation of the compass.