Tuesday, April 8, 2008

State of Charge

Up here in Massachusetts, the boating season seems a long way off. There’s been a layer of ice on the car windshield the last couple of mornings and the weekends have been write-offs. Daytime temperatures were consistently below freezing from November until the first weekend in March. I hadn’t been on board the boat between mid-December and then; partly because it was too cold to do anything anyway, and partly because I’d done a lousy job of setting up the cover. I arrived in mid-January to find it had sagged over the cockpit coamings and in front of the hatchway, forming twin pools that collected enough snow and rain to turn into a pair of 150-pound blocks of ice that effectively blocked access to the main hatch. The forehatch was locked from belowdecks. It was too cold to do anything about it, so I went home, after stabbing a few holes in the tarp for drainage when the inevitable thaw arrived.

In February I went back, and found the pools had grown to the point where a small boy could have ice-skated on them. Fearing their immense weight would damage something, I arranged for the boatyard to attack the ice floes with hammers and cold chisels.

When I did eventually get on board a couple of weeks ago, after ripping the collapsed framework and tarp off the boat, I found some good things and some not so good things.

The good – I’d dreamt that the bilge had filled with rainwater until it lapped at the cabin sole and then frozen solid. Irrational, I know, but there you are. It was actually dry as a bone, bar an inch at the bottom of the sump that the pickup tube hadn’t reached. Knowing that a keel-stepped mast is an invitation for water to enter a boat, I’d emptied a gallon of RV antifreeze into the sump back in November, and left the bilge pump switched on. The antifreeze kept ice from fouling the float switch and everything did its job. What I should have done at layup time was pull the depth transducer so trapped water could find a way out before it rose above the sole.

Also good – the interior smelled dry and sweet, with not a hint of mold or mildew or rust anywhere. Obviously, enough light had penetrated the white tarps to keep the two Nicro solar vents whirring away all winter.

The not so good: Friends who borrowed the boat last year had left a full winecask on board, and I’d forgotten to take it home. The contents had frozen and expanded enough to burst the bladder. When it thawed… you can guess the rest. Thankfully, it was white wine. Sauterne in the bilge leaves a much less distinctive odour than a pinot noir or merlot.

The bad: I thought I had switched the forward electric bilge pump off back in December, but it turns out I hadn’t. It sits in the forward bilge, ahead of the mast, and is one of those that turns itself on momentarily every few minutes to sense the water level, and then pumps the offending H20 into the main bilge. Over the space of two and a half months this, combined with the occasional draw from the main bilge pump, had sucked the house battery dry. It was stone cold dead. Battery electrolyte won’t freeze unless the battery is more than 25 per cent discharged, which my battery obviously was; it scarcely registered on the multimeter, and wouldn’t even take a charge. Inspection revealed that the electrolyte (which I’d topped off last fall) in three of the chambers was below the top of the plates.

Not being as dumb as this makes me sound, I did have an automotive, supposedly automatic float charger hooked up to the house battery. I suspect this was my downfall. The charger had, I think, failed to switch itself off, and had overcharged the battery, leading to electrolyte loss and something horrible called plate sulfation. The battery discharged and froze solid. In short, a combination of carelessness and bad luck had ruined an expensive battery. On the other hand the starter battery, which I’d left disconnected from everything, still showed a relatively healthy 12.5 volts.

So, I’m down $120 for a new Group 27 deep cycle battery. Two, actually, because this spring’s main project was going to be expanding the size of the house battery bank. Maybe I’ll just switch over to LED lights instead. ..


J Duncan Gould said...

It's a sad state of affairs when you're dreaming about the boatyard! Somebody made the analogy regarding those bilge pumps that come on every ten or fifteen minutes that it's like having your car start every quarter hour just in case you needed it. I think the poor pump would come on something like 52,560 times a year; that's dubious engineering. I sincerely hope you get Spring soon, it sounds like you need it! Cheers, Duncan Gould

XML Aficionado said...

Ahhh, the vision of spring and the coming boating season. I launched last week, and - to my great pleasure - found that my batteries have survied the winter intact. I can confirm that the disconnect strategy works best - at least it does for me.
Alexander Falk