Battery Discharge and Polarity?
My lead acid batteries were replaced with AGM batteries 2.5 years ago. At dock, I’m always on shore power with the refrigerator on. I switch batteries between “1” and “2” monthly. This summer, I forgot to turn on the shore power circuit breaker after a sailing trip. When I returned, one of the batteries was completely discharged. I turned on the breaker, turned off the refrigerator, and left the boat on shore power 2-3 days to recharge the battery. Everything seemed to work, until two months later when I again forgot to switch breaker on after a trip and the battery discharged a second time. This time, I switched to the charged the battery, and sailed away for an overnighter. I arrived at my destination, plugged into shore power, and switched to the dead battery to charge. The inverter “cycled” on and off (several loud clicks) a few times and then worked normally.
Yesterday, I switched batteries to the one accidently discharged twice earlier this year. The battery was completely dead. The inverter flashed the “Reverse Polarity” light and "click" loudly. Unplugging shore power and turning off the breaker calmed things down, as did leaving shore power connected and switching to the other battery. I have replaced the shore power cord; the old cord or receptacle appear to have damage or discoloration. I have also been going through zincs rather quickly – replacing them every two months for the past six (maybe started when my first battery drained?). My diver has suggested a “zinc saver”.
- Did I ruin my 18 month old AGM battery by letting it completely discharge?
- Could I have reversed the polarity on one battery and not the other?
- Is it possible to replace ONE AGM battery and not the complete house bank without messing things up further?
- Could the damaged battery be a cause for the zinc corrosion?
I’m at my wits end – and would like to reach out to someone more knowledgeable for help. Thought I’d post this here and see if anyone has input. Thanks for taking the time to read this, and thanks in advance for any comments or input!
Que Sera Sera
1999 Catalina MkII #1738
Wing Keel, Standard Rig
Westerbeke 35B with Obendorfer Conversion