Steve, If you read about batteries, charging (and discharging) you will probably find that starting from "Both" is not the preferred option.
Switching the batteries when the motor is running (or rather, when the alternator is charging) may not be a good idea, but it depends on your switch. If your switch disconnects both batteries and then connects one of them, when you switch from "both" to "1" or "2", you should not switch when charging - you may blow the alternator. However, some switches provide a "smooth" path from "both" to one of the two batteries, so there is a certain load all the time. In that situation, you can switch at will. Some would argue that you should use one battery as "main" and the other as "spare". That way you start from the "main" (and the alternator charges this battery when you are motoring). And you use the "spare", when the "main" is dead or almost. If you switch to "both" right away you might kill both batteries and leave yourself stranded, if one of them was dead (or close). Some very good write-ups on these issues can be found on Sailboat Owners' forum by Maine Sail. Marek (in Ottawa) From: Stevan Plavsa <[email protected]> To: [email protected] Subject: Re: Stus-List Stereo constant 12V Message-ID: <caddevn6om9sdrqrer87ued4gu-r_y92e4oswx3j6c7y4nxq...@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" I have two batteries and a switch. I typically start and run from the "both" position simply so that the alternator can charge both batteries. I heard it's bad to switch while the engine is running. I leave the switch on "battery 1" while away so that both batteries don't drain accidentally. When I go sailing I really only have to run the motor for about five minutes to get out and then five minutes to get back in. I'll need the solar panel to keep my batteries nice and full all season as I plan to do some weekend trips with a two week stint in August. Steve Suhana C&C 32
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