Ever since the exploits of the USS Enterprise way back in the 1960's, vessels have faced the challenge of delivering power to supply increasing amounts of electronic equipment on board. I can remember small sailing yachts where the main bit of electrical kit was a Seafarer echosounder, powered by its own PP9 battery, whose flashing light whizzed noisily around a dial to give a rough estimation of the water depth.
Our recent problems with the failed engine alternator have brought into sharp focus the challenges of power management that we now face. Maunie has a network of instruments (with rather more modern LCD displays) giving us all sorts of useful information about wind speed and direction, boat speed, water depth and so on. She has no fewer than 3 GPS systems, giving our position to within a gnat's whisker, a chart plotter and radar, an AIS transponder and an electronic autopilot; on top of that we have our two fridges, navigation lights, electric water pumps, interior lights and even an extractor fan in the galley. We also plug in our laptop and satellite phone when we need to contact the outside world to update the blog and receive vital weather forecasts. A PP9 battery certainly wouldn't cope with that lot so we have three large 110Ah 12v batteries under our bunk to run it all (and there's a fourth dedicated solely to starting the engine) but, of course, we have to recharge them.
In a marina it's easy - we just plug into the shorepower 240v and an onboard 'smart' battery charger tops the batteries up without us giving it a second thought. On a longer passage, though, (more than 12 hours or so) we have to apply some careful battery management. We therefore watch our battery monitor gauge with great care - it tells us how many amps we're using at any time and the cumulative number of ampere-hours we consumed and it warns us when the battery voltage has dropped to a level that, if we didn't recharge them, we could do lasting damage to the battery cells.
If the main engine's running, it normally (more later on this!) provides up to 70 amps of charge so a couple of hours of motoring will restore the batteries to full health; however if there's a good sailing breeze it's a very inefficient use of a 56hp diesel engine to be running in neutral with only the load from its alternator. So we also have a small diesel generator which provides about 40 amps and uses a quarter of the fuel (it's a lot quieter too) and we'll run that for a couple of hours in the evening to ready the boat for the high electricity usage at night and then again in the morning to replace the energy used.
We're trying to be green on this trip, however, so burning diesel is something we're aiming to minimise. So we've replaced all the light bulbs with high efficiency LED's and we've installed two solar panels which will deliver up to 5 amps in full direct sunshine. Some boats add a small wind turbine mounted on a pole at the stern (we've decided against that at the moment as they can be really noisy and add yet more weight where we don't want it) and there are some clever generators which have a small propeller hung over the stern to use the energy of moving water to create charge (they are pretty expensive and slow the boat down); we're hoping that a combination of careful energy management and our solar / generator combination will work ok..
The postscript to our alternator story is that, although it's generating electricity once more, the recharging regime is not working as well as it did previously. We managed to get hold of Antonio the electrician again, via the very helpful yacht club in Baiona, so did an unscheduled stop there this morning. Antonio came back aboard, this time with his helper, and spent a good 45 minutes checking everything. I'd already come to the conclusion that he reached, which was that when the the alternator failed it also destroyed an add-on 'Sterling' charge controller. This clever bit of kit fools the alternator into delivering more power than its own regulator would call for, thereby shortening the engine running time to recharge the batteries. Replacements aren't available here so we will have to contact the makers to see if we can get one shipped to a suitable location. In the meantime, though, we're still a going concern so are planning to head into Portugal tomorrow. Antonio was apologetic that he couldn't resuscitate the Sterling controller and refused to take payment for his extra time today.
We're currently anchored off a beautiful beach at the north side of the entrance to Ria de Vigo after a brilliant sail across from Baiona ( a beat in a Force 5-6 so we reefed down); we're ideally placed for an early start in the morning. Graham took advantage of the evening sunshine for a swim and snorkelled around the boat to give the hull a good clean for that all-important extra tenth of a knot of boat speed. We'll check the wind forecast again this evening but it looks pretty good so we hope to be in Povoa de Varsim before dusk tomorrow.