Two batteries switched?

[rookieflyer]

The old Marine Electronics Bible, much of which I find is now out of date, made several statements about dual batteries. One warned about switching batteries in & out while running because of the switching spike generated by the inductance in the circuit when opening the connection. I believe this applies to the typical battery switch, which breaks one connection before making the next. If you are simply switching from two batteries in parallel to one, I don' think it applies. The other, and it sounds like you are aware of this is that the weaker battery will pull the stronger one down. The weaker automatically becomes a load and the stronger attempts to supply current to it. If they sit together connected and balanced they become difficult to charge.

After reading some of the posts, I think the most important thing to do with batteries is to mount them properly. My boat is almost exclusively run on the Gulf,which is notorious for changing from glass to choppy & vice-versa. Anything less than good-solid bolt-down kits would make the batteries dangerous projectiles...

The automatic switcher is a nice idea, but I would want a good display on the dash to tell me what's going on with it.

[Techno]

I think most of the marine switches are a make then break type contact. But there may be some that aren't. They say on the package usually.

For my use I can't really see a need to switch the batteries while running. If one is dead then I would switch to the 2nd. I would know this from either the engine not starting or dieing.