The refrigeration unit should be running off the house batteries, not your start battery (if you have installed). I don't believe a separate starting battery was a factory installation. Could be previous owner installed one, you will need to check to see how this was wired.

I can run my refer onvernight without drawing the battery down to a discharged state. You may want to get them and your charging system checked. Like everything else, they tend not to work as well once they get aged.

I'm sure there are others on this site that can offer you additional guidance.

dmotter,
It would help to know a little more about your boat. MkI? MkII? Hull #? Perhaps you can update your signature to automatically give readers this info? I agree with Allan. From the factory, all C36's came with a pair of deep cycle batteries. One wired to the #1 switch position, one wired to the #2 switch position. If your boat has a separate starting battery, all the better. If your boat has a separate starting battery, AND a larger house bank, better still!! As Allan stated, you have to do a little investigating of how your boat is now wired. Factory wiring diagrams will mean nothing to you. From your description, I can make a wild guess that your #1 battery is the starting battery, which is why it ran down overnight. The typical A/B refrigeration system draws about 5A, and should cycle on 50-60% of the time (depending on ambient temps, how often it is opened, etc.). Add to that your typical house loads (lights, water pump, stereo, etc.), and you are looking at a typical draw of about 100 AH per day. Your house bank may be in the 3-400 AH range, but your starting battery is less than 100 AH. Also check for corrosion, loose connections, and undersized wires. Any of these can dramatically reduce the charging effectiveness and the battery capacity. Hope this helps.

Dave-A suggestion if you are not sure about the health of your batteries.

You could have your batteries checked for condition at a battery shop. They can do a load test and give you an idea if they have life left in them or are on their way out.

Laura Olsen
S/V Miramar #938

Dave
To determine which is your House Battery switch and which is your Starting Battery switch just take the wires off your starting battery, set you battery switch to #1 and push the starter (with the key on of course) if nothing happens then your starting battery is switch #1.

You can do the same thing by turning on a cabin light after you disconnect the starting battery and set the switch to #1 then switch to #2. Whichever switch energizes the light is your house battery because the Starting Battery is disconnected. Don't forget to turn on the "Cabin Light" switch as well as an individual light.

At our Club a bunch of us chipped in a few dollars each and bought a battery load tester like the mechanics have. It was not to expensive and we keep it in the Dockmasters office. Now we all can check our batteries under load whenever we want to.

Dave - As Tom suggested, it's worth your while to document how your 12V system has been enhanced. I re-did mine about three seasons ago and I occaisionally have to go back and confirm on my drawing how the fusing and breakers are configured. For example, my Xantrax XC-30 shore charger will equalize my flooded batteries. To protect electronics, I just need to trip the circuit breaker inside the battery compartment to keep the high equalization voltages away from the directly connected devices attached to the battery selection switch.

So, in short, I'd aquire a low cost multi-meter, rig up long conductor with some small aligator clips and do a little continuity testing. If you're lucky, some of the wiring is labeled.

Bottom line is that the more you know about your boat, the safer you'll be on the water.

Craig