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sailhog 11-23-2007 02:21 PM

12 volt problems...
Yesterday the family and I sailed from HHI to Beaufort, SC where we spent the night at the downtown Marina. Barbequed some shrimp, drank lots of beer and wine, played monopoly with the kids, the little ones watched a movie. We all had a great time. We went to bed with two lights on -- the nav desk and the head.

This morning, however, I awoke to very dim lights. We were plugged into a 30 amp shore power port, so I assumed the battery charger would keep the batteries topped off. The battery charger, however, was out of order. It took some futzing with the dock staff, but I finally got a battery in there, got the engine started, switched the batteries out, and recharged my dead batteries. The engine recharged them just fine, and so we sailed home. Being that I was in a hurry to make the tides down the river, I discovered that I had no 12 volt after we were underway -- no GPS, no depth. We decided to go on, and sailed right up to our dock. Started the engine, and parked it.

So... the 12 doesn't work -- no cabin lights, depth sounder, etc. I had some 12v current first thing this morning, but no more. I checked a couple of the fuses while underway, but they were fine. However, I did not check them all. So my question for the learned panel is: Where do you suppose the problem is? I don't have a breaker box, but a fuse box. I have two batteries -- one of which is a dedidicated starter. Could my shuffling batteries around this morning have done something? Are 12v fuse systems like Christmas tree lights in that if one is out none will work? I appreciate your help.
Happy Thanksgiving to you all,

Faster 11-23-2007 02:32 PM

It sounds like your batteries are either dry or completely pooched. A dry battery will come up to voltage quickly but has no amphour capacity so only lasts a short period of time.

Check your fluid levels first, fill and recharge. If they don't recover you may be stuck with buying new batteries.

They may have gone dry if you charger was overcharging for a period of time. In any event when you leave a charger on at the dock you really need to periodically check the levels - every month or two anyways.

sailhog 11-23-2007 02:35 PM

The batteries are fairly new, and this is the first time they've been run all the way down. They came right back once the engine had had a chance to recharge. Also, wouldn't the depth sounder, cabin lights etc. work once the engine was running?

sailingdog 11-23-2007 02:45 PM


You still need to check the water level in them if they're wet cells. It does sound like your house bank is blown.

Also, if you have a battery switch* like mine... it doesn't combine the banks, and isolates the house side from the starting side.. so unless you had a battery combiner, the alternator would only charge the starting side, and wouldn't run the house-side electronics unless you have the switch in the "combine" position.

*BTW, the battery switch I have is a BlueSea Dual Circuit Plus...

bestfriend 11-23-2007 02:47 PM

Check each cell individually. Check all your connections and clean them all. How new are the batteries?

sailhog 11-23-2007 02:52 PM

I have a batter switch with settings for: Off, 1, 2, and both. It was in the "both" position last night. The batteries seem to be recharging just fine.

sailhog 11-23-2007 02:52 PM

The house battery is 6 months old and the starter is about 2.5 years.

bestfriend 11-23-2007 02:55 PM

If you had it on both, you drained them both. Next time, put it on whatever one is your house bank only. That way you will still have your starter battery in the AM, can start your engine, and recharge. If you have them on a trickle charger now, let them go overnight and check it again tomorrow. If the problem persists, clean the connections and check the cells with a tester. If it still doesn't work, you may just have a bad battery. Do one thing at a time so that you can isolate the problem for future reference.

2.5 years could be it for your starter battery. Its best to have them both the same age or the old one will hurt the new one.

Off to the boat, best of luck.

TrueBlue 11-23-2007 02:57 PM

If the battery banks are both fully charged, hold at least a 12 volt charge, and none of your 12 devices are working while underway, there's obviously a short or poor wire contact somewhere in the electrical system.

You'll need to test the circuits for continuity, starting from the batttery terminal posts to each device to find the fault.

sailhog 11-23-2007 02:59 PM

I had them on both last night in order to recharge them. I'm thinking I made a stupid mistake... The only time I plug my boat in is when we're overnighting at a marina. I still don't see why these 12v functions don't work when they've got enough juice to start the engine.

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