These days shore power is part of marina life. There's no denying the convenience of being able to plug in, so that your fridge can be kept cool and your water hot, without running the engine.
Traditionalists who keep their boats on swinging moorings may deplore the decadence of it all, but it's good for your boat to leave it with a dehumidifier plugged in and running during the cold, damp months, and maybe a low-level background heater, too.
When you're working on the boat, it's great to be able to plug in power tools - or a pressure washer. For many, it's also a bonus to be able to plug in a laptop without worrying about battery drain. And shore power means you can keep your batteries topped up, too, of course.
But can all this convenience lull you into a false sense of security? When we did the North Sea Race the other week, we were surprised how fast our batteries went down, with just the navigation lights and instruments running. (We switched off the fridge because we'd put enough frozen food in there to keep it cool).
You're allowed to run your engine out of gear to top up the batteries during a race, so this wasn't really a problem. But then we were astonished to find the voltage was dropping again, within a short space of time. And with 200 Ah to run all the domestic services, there really shouldn't have been a problem at all, in a race lasting just over 24 hours.
Looking back, we'd only had a problem once before, on an overnight passage last year, when the autopilot was running in quite big seas, and we'd assumed that was what was draining the power. And of course, as soon as we'd tied up in the marina, we connected the shore power, switched on the battery charger, and thought no more about it.
And as we have access to power in our home berth, the batteries are routinely charged whenever we're on board. We don't leave the charger running all the time, as some people do, having been advised not to. But we'll often go down to the boat on Friday evening, say, before leaving early on Saturday morning, so we put the charger on to run the fridge, lights and so on until we leave.
So we never actually needed to ask ourselves how healthy those domestic batteries really were. We replaced the engine starter battery soon after we bought the boat, because it was obviously struggling. With hindsight, that should have made us query the state of the other two as well.
The boat was two years old when we bought her, in “as new condition” according to the survey report. We should have realised that the extremely low log and engine hours readings, which contributed to that pristine state, would mean that her early life had not been particularly kind to the batteries. And we've been using her a lot harder for the two years plus since we've owned her.
We've topped the batteries up with distilled water as needed, of course, and there's been no obvious problem - until now. But now we've been forced to face reality, and added to all the other expense of getting the boat ready for the Fastnet, the list of bills will include two new batteries.
If you keep your boat in a marina, routinely attached to shore power, it may be worth asking yourself how healthy your batteries would be if you detached them from that charger.
Most of us only day sail for most of the year, starting the engine to get in and out of harbour, and between that and the shore power, even quite sick batteries will continue to do the job without calling attention to their plight.
But it's at this time of year, when we set off on longer holiday cruises, that any problem is likely to manifest itself. So don't wait for the wisdom of hindsight. It's worth thinking about how well your batteries would be without that addictive shore power lead before you unplug it!
