We have had a worrying few days aboard the good ship Maunie. Our 'domestic' batteries (3 large, 110Ah 12v lead-acid jobs which run on a separate circuit to the engine-starting battery) were suddenly losing charge at a frighteningly fast rate. Overnight, after a healthy recharge from the solar panels, the voltage would drop very quickly (even with the fridge turned off) and we feared that they had all suddenly failed – after 5 years and lots of charge and discharge cycles. We were a bit puzzled, though, since we are very careful not to let them discharge below about 40% of 'full' but we had no experience of battery failure on a boat to compare. We knew that they were getting on a bit (5-6 years is a pretty good lifespan) but expected a gently decline and instead we were seeing something much more dramatic.
Graham was particularly fed up with himself for not getting the batteries capacity-tested before we left (it needs some specialist kit) and had discovered that it's not possible to get them air-freighted (even if we could afford the cost) so it looked unlikely that we'd be able to get anything here other than a normal car battery which is not suited to the deep-discharge cycles aboard a boat.
Thankfully our friend Colin on 'Ithaca' is still in Opua and emails and SSB voice messages to him resulted in immediate offers of help and advice. He contacted a local boat electrics specialist in Opua, Rob Whalley, who kindly took the time to email us over the weekend suggesting that our problem sounded like an internal short within one of the batteries which was then robbing the power from its neighbours. We carried out the test he suggested – disconnecting the batteries and testing them with a volt meter after a couple of hours – and, sure enough, two batteries were still at 12.7v and one was down to 10.9v.
So we've now isolated the dead battery and the other two seem to be fine – we should be able to get a replacement in Fiji but in the mean time we can carry on and stop worrying about imminent power black-outs! We're very relieved and happy and, once again, the value of ever-helpful sailing contacts made via our radio net has been demonstrated.
We're back in Neiafu for a couple of days – a chance to restock on fresh veg and fruit from the market and other food items from the Chinese-run stores. Last night we had a great farewell dinner with Lionel and Irene on Kiapa; they set sail for Fiji this morning but we hope to catch up with them somewhere over there. Irene made Graham's day even better (after the battery fix); when Di said he'd celebrated a 'big' birthday in March she said, in all honesty, 'Your 40th?"