I have a little "smart charger" in the van which trickles the house
battery when I connect the side inlet to household AC power. But I
unplug the extension cord before starting the van, and turn off the van
before plugging in the extension cord.

But there have been a couple times when I've accidentally fired up the
van with the extension cord connected and Nothing Bad happened, but I
think that's going to be a function of your AC-powered charger. My guess
is that with the alternator applying power to the battery, the charger
will look at that and say, "Uh, I dunno," but not blow up or anything.

--
Jack "Rocket j Squirrel" Elliott
1984 Westfalia, auto trans,
Bend, Ore.

On 09/20/2012 01:37 PM, neil n wrote:
> I hate to ask this in the midst of truly electrically qualified people
> but.....
>
> When van running, you're off shore power? IF so, alternator does it's
> job, charger not connected.
>
> When van not running, you're ready to connect to shore power.
>
> Or is there concern that the van might be running while charger still
> on. IF so....
>
> Maybe install a relay between DC charger output and house DC system.
> Have it trigger via alternator blue wire. Or is there too much lag time?
>
> Neil.
>
> On Thu, Sep 20, 2012 at 9:51 AM, Rocket J Squirrel
> <camping.elliott@gmail.com <mailto:camping.elliott@gmail.com>> wrote:
>
>     I'm looking at rewiring my house battery charging system.
>
>     I want to be able to switch between charging the battery from the
>     alternator ..... and charging off my
>     3-stage DC > DC deep cycle charger
>
>
>
>     To do this, I'm looking for a manual 3-position battery switch. I've
>     already looked at West Marine's offerings and I can find either
>     two-position (off/on) switches, or four-position (off/1/2/1+2) switches.
>     The latter could be used but it's dangerous as the 1+2 position would
>     connect the DC > DC charger's output to its input, resulting in a
>     collision of universes and possible smoke.
>
>     Two off/on switches could be used, but again, it would be possible to
>     accidentally turn them both on, resulting in that collision of universes
>     thing.
>
>     Anyone know of a three position (1/2/off) battery switch?
>
>     --
>     Jack "Rocket j Squirrel" Elliott
>     1984 Westfalia, auto trans,
>     Bend, Ore.
>
>
>
>
> --
> Neil n
>
> 65 kb image Myford Ready For Assembly http://tinyurl.com/64sx4rp
>
> '88 Slate Blue Westy to be named.
>
> '81 VanaJetta 2.0 "Jaco" http://tubaneil.googlepages.com/
>
> Vanagon VAG Gas I4/VR Swap Google Group:
>
> http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines
>