I have read some on this topic in the forum and still have a question regarding advice on how to use my duel battery switch. First some details. I recently purchased a 2004 Hunter 36. I think the previous owner had made some changes to the battery set up based on what I see in the owners manual. The current set up as best I can tell is as follows: 1. I have two battery banks. 2. Battery 1 is a single 12V starter battery. 3. Battery 2 is a bank of four 6V batteries configured to provide 12V with a capacity of 220 Ah. This battery has an electronic battery monitoring system attached to it to keep track of current, voltage, amp hours used, remaining hours, charge state. 4. The boat is normally in a slip and connected to shore power under most circumstances and I mostly day sail so I never think about having adequate charge. 5. The battery charger is a 30 amp charger which charges each battery separately through the battery selector switch. When the battery charger is turned on it will always charge both batteries regardless of how the battery switch is set. 6. The engine alternator will only charge the battery bank that is switched on at the battery switch at the time the engine is running. 7. When I bought the boat I was told to keep the battery switch set to "both". 8. Never ever change switch positions while the engine is running. Based on what I have read here it would appear that the "set to both" advice is really bad advice. Each battery bank is quite different and therefore should not be connected to each other for an extended time and it would be possible to run down all the batteries leaving no emergency reserve. I did this once already by forgetting to turn on the battery charger and the refrigerator (on always) ran down both banks. I believe switching from bank 1 to bank 2 on odd and even days wouldn't work in this scenario. So what I am doing is this. I keep the battery switch on 2 all the time which is my house bank and leave battery 1 as my emergency to start the engine if necessary should I run down bank 2 after a day of sailing by not paying close enough attention to the charge state. Every once in a while I will start the engine using battery 1 just to make sure that it is charging. My question relates to what do I do when cruising? I am going away for a week (first time I have been away from shore power that long). I am a little paranoid that I will run down my house bank 2 and find that battery 1 has lost charge either due to not being charged daily or because of, for example, the bilge pump ran it down which is not likely but possible I suppose. When I am running my engine only and while cruising does it make sense to keep the switch set to "both" so that both batteries are charging when the engine is running and then switch to battery 2 when the engine shuts down?