You learn something new about your boat everyday. For example, we recently discovered that our freezer is hooked up to the battery that is dedicated solely (at least we thought) to starting our port engine. The reason for having dedicated batteries targeted for engine starting is so that if you find yourself having drained the bank of house batteries, there’s no wind to sail or there’s an emergency and you need to make a quick exit, you can always start your engines.
Since buying our boat, we’ve never been away from it without starting the engines for more than 10 days, so there’s no way we could have known that the pump that is used as part of running our freezer gets its power from the port starter battery. This starter (and I guess now freezer pump) battery is not on the inverter/charger that keeps our house batteries and starboard engine starting battery charged. Therefore it does not get charged without running the port engine and having the alternator charge the battery. It had been over two weeks since we had started the engines, and it appears that the freezer (which actually runs on 110 volts either from shore power or by running our inverter or generator) completely drained the battery, even though we were on shore power. The small 12 volt sea water pump that is connected to the port engine battery used to pump water for use in running the freezer was the culprit that actually drained the battery.
How did we discover that the freezer pump drained our port starter battery? First, the freezer indicator light went to low battery, and we thought something was broken, since we’d been on shore power. We searched online to find a solution but could not. When we decided the next morning to take the boat out in order to start the engines, empty the heads (toilets), and make some water, the port engine wouldn’t start. However, the starboard engine started just fine. This was one time that I was elated that that engine wouldn’t start. It explained the low battery indicator light on the freezer!
We actually have a charger for our port engine battery but we’ve never used it. It was explained to us when we bought the boat to be a back up in case our main inverter/charger did not work. If the battery isn’t being used there is no real need to have the charger on. (Of course for extended non-use you would probably want to keep a trickle charge on the battery.)
So, in order to start our port engine, we have a back up switch that will allow us to start the engine with our house batteries (in case our starter batteries are drained). We then recharged the battery with the alternator. Once we did this the freezer worked again and the engine started again – no problems!
Every boat is different. Systems are different, wiring is different, technology is different. Just when you think you understand it all, it throws another curve ball at you. It’s a great way to keep exercising your problem solving skills, that’s for sure. Lesson learned: we’ve now turned on the port battery charger so that the shore power will also keep that battery charged as well as keep our freezer running. All’s well that ends well.
-Michael (in Mazatlan)