...but like Bob, we are hooked to shore power most of the time and when we are not even when running the fridge for half a day it does not "Kill" the battery...
The difficulty with this approach is that one rarely knows when a bank is dead until "you're out there." Keeping them "charged" on shorepower ALL THE TIME is also not good for banks. Constant float creates sulfation.
FYI - One of my 4D AGM batteries decided to kill itself this year. When we arrived at the boat, there was a horrible sulfer smell. You could hear the one battery "boiling" internally and the outside casing was extremely hot. Shore power was hooked up and the battery charger on. Even after the power was cut, the battery was still boiling due to the other battery feeding it juice. After the batteries were disconnected from each other, the boiling finally stopped.
Not sure about the age of the battery, it was from DEKA. Boat is a 2001. Last season I remember a lot of corrosion on the battery terminal, not sure if this was a sign it was going bad or not. Replaced with 4D's from Interstate Battery. WM was too costly.
Not sure what would have happened if we decided not to come down that weekend.....
This is a perfect example of the first quote. Maine Sail has mentioned many times: "Batteries don't kill themselves, they're murdered."
Perhaps this skipper did the right thing, but...
And 4D batteries are NOT true deep cycle, and they're back killers.
Really, I suggest that those of you who are ALWAYS on shorepower do a simple test, maybe even once a month: FULLY charge your house bank and then DISCONNECT from shorepower.
Then, you will see what is really happening the next time you come down to the boat.
Most folks seem to get it backwards: "My bank was fully charged when I left the dock."
The real world issue {for those of you who are NOT marina hoppers (and this could be many of you and is a description of activity - how YOU use YOUR boat, and is not meant in a negative way at all} is that the challenge is to spend a night on the hook or unplugged, and run your normal loads. In MOST cases, a good daily draw with a fridge is +/- 100 ah.
Like this:
Record of Daily Energy Use of 100 ah per day:
http://c34.org/bbs/index.php/topic,6353.msg41471.html#msg41471
One must work THE OTHER WAY: "How does my system work when the bank is DISCHARGED for a night or two," NOT how it works when it's full to start off with.
This is for those of you who prefer to disconnect from shorepower, whether it be a trip or an overnight at your favorite anchorage.
Give it a try sometimes, you might find out things you never knew. :dance:
Maine Sail's discussion of AGMs is VERY worthwhile reading. The main point is that they fail without warning. IN many boating forums, recently, I've seen questions like, "My AGMs are 9 years old, should I replace them?" It's kinda amazing, the same question in four different forums. In all cases, I refer them to Maine Sail's link, and this one, too:
AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
http://forums.catalina.sailboatowners.com/showthread.php?p=848465&highlight=darn agm
That is why, for most of us frugal boat owners, AND who have reasonable ACCESS to our batteries, wet cell remains the most bang for your buck way to go. Others, who have difficult or NO access, yup, AGMs, but I'd go gels first.
Your boat, your choice.
All the best,
Stu