About a week ago my wife, Debbi, and I left Fort Myers Beach, Florida on an overnight sail to Marathon in the Florida Keys. The conditions were just about perfect. We had a 10-15 knot breeze giving us a classic port side beam reach on a sunset sail. Then the the Auto-Pilot spoke to us.
When Your Boat Speaks to You
by Hugh Marlor
Our boat like most cruisers has a set of “house” batteries that provide electricity to items such as lights, and water pumps. There is also a separate starter battery. The starter battery and the house batteries are connected by a single circuit that is connected to the engine’s alternator which charges the batteries while the engine is running.
Fail-Safes for Battery Conservation
There are a set of switches that allow you to remove the starter or house batteries from the main electrical circuit. For example, when anchored overnight it is a good idea to turn the switch for the starter battery to off so that your anchor lights, fridge and water pump do not possibly drain the starter battery overnight. While on a long sail we flip the starter battery switch to off to disconnect the starter battery from the main electrical circuit. This prevents the house batteries from draining the starter battery over the course of being under sail for extended time.
Of course something always has to come up on overnight sails. A few hours after dark our auto-pilot began to make a beeping sound. The beeping was initially intermittent, and then became constant. The auto-pilot was still working, but something was amiss. We checked the auto-pilot manual, which told us that this beeping sound is the auto-pilot detecting low voltage from the electrical system.
When All Else Fails – Sail
When we put the starter battery back in the main electrical circuit the beeping stopped. The question then became: Were the house batteries failing, or was there something on the boat that was putting an extra load on the house batteries, and causing their voltage to drop? We noticed that the house battery voltage level seemed to be dropping more quickly than usual. We had a good breeze for sailing, so we started the engine and put it in to idle. Since the engine’s alternator feeds electricity to the batteries while running the auto-pilot stopped beeping. We continued on our overnight sail under a sky full of stars, and a beam reach.
After arriving at in Marathon and docking at Faro Blanco, we needed to determine if the house batteries were failing or if something else was using more electricity than necessary. For example, we noticed that our freezer compressor seemed to be starting and stopping more often than usual. This could be an indication that the compressor’s internal mechanisms are about to fail.
In order to test the house batteries we purchased a 100 amp battery load tester. These run about $25 and will tell you if your house batteries are not working properly. You simply charge your house battery, disconnect the cables and connect the load tester like a standard battery charger. If any of the internal cells on your house batteries are failing, this device will let you know. We found that our house batteries were just fine. We suspect that it is the compressor on our freezer may be the culprit. Before our next passage will have a refrigeration expert test both our compressors.