[QUOTE=tim_farrell;9440]
You guessed it, the boat wouldn't turn over when I went to start it. I took two of the three batteries home and charged them overnight - came back in the AM and she started right up. I then motored around for an hour to ensure the 3rd battery charged.

Is 9.5 sufficient to drain your batteries? I rarely use my motor - only enough to get to open water (10 min) to get the sails up. I am contemplating a routine of running the engine for 1 hour every other time I go aboard - just to ensure a full charge. Any one have this happen? Am I thinking about this correctly?[/QUOTE]

9.5 hours shouldn't be enough to drain your batteries, even in this weather. We have 225 amp hours in our house bank (2 6v golf cart batteries) and it seems to take about 2 days to draw them down to 50% with the fridge running and careful use of lights, etc.

The bigger question is why your starting battery went dead, since it shouldn't have been hooked in to run your fridge. ... You are wired to isolate it from the house circuit, no?

Batteries are pretty much of a mystery to me but, most diesel people will tell you to run your engine not "under load" for an extended period is not good for the engine. An engine is much more expensive than a battery.

Tim, I guess my question is, how are your batteries wired? Do you not have a dedicated battery for starting only? If not, you may want to consider changing them over; that way you will not have to worry about starting the engine to get out of nasty weather. Regarding the question of running the engine to charge up your batteries, I have always heard from diesel experts that it is best to run the engine under a load.

Tim,
If your current batteries are all deep-cycle, the simplest and easiest way to go is to combine them all into one house bank, and then add a dedicated starting battery, that is NOT a deep cycle. Any regular car battery would do fine. Have the alternator output go directly to the house bank, and get an echo charger to take care of charging the starting battery. You could even use the existing 1-2-B battery switch. Use the house bank for everything, and then if you have a problem, you will have the starting battery in reserve. Let me re-phrase a couple of the double and triple negatives in previous posts. You SHOULD run a diesel with a load. Just charging the batteries at high idle is not a good thing to do with a $8-10k diesel engine. You would be asking for problems in the future. A bigger question is why you ran out of amps after only 9-10 hours. Something is wrong. Are the batteries old and tired and about to die? Have you cronically undercharged the batteries, shortening their lives? Do you have some big energy drain you are not aware of? Even bigger question is do you have some type of battery monitor so that you know what's going on, rather than guessing??? Many owners have installed the Link 10 and been happy with it (now the Link Lite or Link Pro?) With the stock alternator/regulator, it would take MANY hours of motoring to bring depleted batteries back to life. Lots of things to consider. Your boat, your choices, your money!

Tom's right. If you would like a "primer" on boat electrical systems, try this: Electrical 101: [url]http://c34.org/bbs/index.php/topic,5977.0.html[/url] from this "101 Series" of topics, [url]http://c34.org/bbs/index.php/topic,6437.0.html[/url] You may also want to consider a solar panel.

I lived on a mooring for 5 years. It seemed the batteries were always flat due to undercharging. A standard alternator and regulator would take 5-6 hours to bring the batts back up. I had to supplement charging with a 2000 watt Honda generator. They are very quiet and fuel efficient. It will run the microwave and all of the Christmas lights while watching a movie during the evening recharge. The other posts did a great job stressing the importance of keeping the batteries charged. They don't last long when undercharged.
Good luck!

The whole subject of batteries and charging is a LARGE chapter in a book.

But, IMHO running the engine on the hook or mooring to use the alternator for charging is not something you want to do on a regular basis. Getting set up with solar panels and/or wind generator is an expensive option, but worth it for the long term if you anchor out a lot. Alternatively, having a small, quiet portable generator is another option, but requires you to carry more gasoline than perhaps you want to.

As for your statement, Tim: "I am contemplating a routine of running the engine for 1 hour every other time I go aboard - just to ensure a full charge." That will never ensure a full charge for the reasons others have stated.

Good luck with your choices.

[QUOTE=tim_farrell;9440]

Is 9.5 sufficient to drain your batteries?[/quote]

That question can only accurately be answered with more data. The obvious answer is no but it all depends upon the age and condition of the batteries and what was running. For example if you had the fridge going with an inverter running a laptop and some instruments you could be approaching 10 amps per hour or 95 Ah's...

[QUOTE=tim_farrell;9440] I rarely use my motor - only enough to get to open water (10 min) to get the sails up.[/quote]

And here's the problem. With 10 minutes of charging your probably replacing very, very little. Lets' say you have the stock 55A alt that will put out about 45-50A max. So now you run it for ten minutes in bulk and you get only about 8.3 Ah's returned. But you go racing/sailing and use 10 Ah's so now your battery is constantly giving up more than you put back. Your bank could have easily been at 45-50% state of charge before you ran it for 9.5 hours..... Also that ten minutes is not necessarily good for the motor as it usually takes longer than that to burn off the internal start up condensation.

A battery monitor is a GREAT TOOL!:D

[QUOTE=tim_farrell;9440]I am contemplating a routine of running the engine for 1 hour every other time I go aboard - just to ensure a full charge. Any one have this happen? Am I thinking about this correctly?[/QUOTE]

It appears you're on a mooring and should really contemplate a solar panel and charge controller for the way you're using the boat...