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Batteries discharge too quickly?
Hi all,
This summer, for a couple of reasons, I took the 110 VAC power cord off line. I had tow periods then when I was away from the boat - the first was a couple of weeks, and the batteries were down, but not completely discharged. That day, the engine started, but we did not run it long enough to charge up, nor did I connect the power when i left. Then, due to some unexpected medical BS (which is what prevented me from running the boat and charging her up at that first spot when I saw they were low), I was away from the boat again for another 5 weeks.
When I returned this time, the batteries were very nearly discharged. I was able to get them back up, but along the way, the Heart overloaded and had to be reset, then I was getting really funky high (250 amp) draw readings on my DC panel, associated with a low voltage (6 volts) - I was able to make that 250 amp indication disappear by turning on the tri-color light (when I tried turning on other DC loads, not all of them shut down that draw, so there is something there - which made me think of diodes and back flow of current, but everything was so screwed up at that point, who knows? less than 6 volts in the batteries, the Heat pushing for all it was worth, etc) So I left the tri-color on, and kept her on charge, and within an hour, the voltage was up to 13, and we were ok to start the engine. We ran it for 4 hrs as we brought the boat north for the winter.
She is now plugged in to 110 dockside, with no loads (again except for intermittent bilge - and I should say she doesn't take much water - a little comes in when it rains hard, but even then not much). I will be up there tomorrow doing some winterizing related stuff, I expect to see the batteries at full charge, and everything else in order - we'll see.
There are three boxes of AGM batteries, presumably two (440 AH) for the house and one (220 AH) for starting. I have to get into the paperwork to make sure of all the details of her electrical system and wiring, I have not yet had to do so - but the purchase information was that the batteries were all new in 2006 as was the Paneltronic panel, combiner, and most of the wiring. It all got a good bill of health on the survey, except for reversed polarity of some AC outlets, which doesn't really concern me much personally. I know the previous owner probably had the batteries on the charger all the time. The boat was in San Diego, so that is 24/7, no winter haul out.
I did not shut off the selector switch when I was to be away from the boat, since the auto bilge pump circuit requires this switch to be on, to bring power to the panel. In previous boats i have run those auto bilge power lines, hot and ground, straight to the batteries, with a fuse on the hot line right at the connection. That way I could otherwise isolate the batteries by shutting the selector switch off, and prevent leakage of current from so many possible paths. Anyone think this is a good approach to continue? My thought when I bought this boat was 'it ain't broke, don't fix it', but as time goes on, we all make adjustments we like, and maybe I should do this one too, but will be interested to hear what you folks say about it.
I do not know if there should be an ordinary or zener diode between the Heart rectifier and the batteries on the hot side - all I do know is that other than the bilge pump, there should not have been any active 12 VDC draws, and I have never seen any indication otherwise of an obvious leak down of the 12 volt system on trips of several days with a full complement aboard.
When she is hauled next week, the yard will put a capacitance tester on the batteries and report to me how much life is left in them (I have to study up on that and 0 maintenance batteries in general so I can understand the test approach and how reliable the results are - I feel undereducated regarding these battery types, but now I will have plenty to read in the winter time).
I guess I am just looking for ideas - am I just expecting too much from the batteries? They say the AGM non maintenance types should be good for full discharge, last 10 years, all that good stuff - but how long should they hold a decent supply of juice when left off-charge in conditions I described? I would have expected a little loss of cranking ability, but was surprised to find them so low.
Anyway, that's enough on this topic, any ideas would be appreciated, and I will report back what I find, for this situation and also regarding my little rock strike from July - since she will be hauled for the first time next week since that event (I really expect nothing more than some chipped paint - but we'll see and I will report to the forum).
Thanks, as always -
Geoff
Corazon
Swan 411 #41
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