Now I never leave the dock without one of those portable car-starting batteries, completely disconnected from everything.
We had a very similar story, except we were the first to rent the boat at the start of the season and the battery bank hadn't been very well tested before they gave it to us -- a few had gone off over the winter. They drove out from HQ, replaced the bad ones with fresh stock from their van, and sent us on our way.
"I sailed from Deptford, April 9th, 1772, but got no farther than Woolwich, where I was detained by easterly winds till the 23d, when the ship fell down to Long Reach, and the next day was joined by the Adventure. Here both ships received on board their powder, guns, gunners' stores, and marines."
[http://gutenberg.net.au/ebooks/e00044.html]
So the "Resolution" managed about 8km on the day of departure from the London naval dockyard, then remained anchored in the river for 13 days waiting for the wind to change direction, finally managing 16km to the victualling dock.