It seemed like we’d been forgotten after lunch so I went to enquire. It transpired the battery testing kit was not on site though, so even after we’d been remembered we were no further forward. It being Friday afternoon, nothing was going to get fixed until Monday. We agreed to come back in a week or so. If his theory is right and the battery decays further, we do have a work-around. The bow-thruster batteries are identical to the starter battery, so we’d “just” need to carry one the length of the boat and connect it up.