Yup, diodes would (mostly) work in this situation. Keep in mind that
diodes have a voltage drop (.4 to .7 volts, depending on types) that you
need to deal with in battery charging applications.

Many of the cheap solar battery chargers have a built in diode.

Jon

On Wed, 18 Jul 2007, Brendan Slevin wrote:

> I am by no mean an electrical guru, but, might diodes work in this
> situation?  My understanding is they are one way streets for current.  Seems
> they would keep the charging from the alt. from getting back up the line to
> the solar and smart charger.  Also, you could hard wire everything in to a
> selector switch, possibly a headlight-type, three way switch.  OFF-no aux
> charging reaching the battery (only alt;) Position 1-Solar Charging;
> Position 2-Smart Charger.  Let us know what works out.
>
>
>
> Brendan Slevin
> 84 GL Totoro
> I have measured out my life with coffee spoons. -T.S. Eliot
>
>
>
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf Of
> Loren Busch
> Sent: Wednesday, July 18, 2007 9:52 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Aux Battery Charging Alternatives Question for the Electrical Gurus
>
> Right now I have wiring in place for three ways to charge my aux battery.
> First, and permanently connected, is the alternator when engine is running.
> The next two are wired right now so that only one can be connected at a
> time: Solar charge controller (and solar panel) and an onboard 30 amp
> 'smart' charger.
> Question:  What kind of problems, if any, would I encounter if all three
> were connected to the battery at the same time?  Assuming that only one
> would ever be running at any time, would I expect problems such as the solar
> controller seeing the voltage from the 110v ac charger and causing damage?
> Or the solar controller seeing the voltage from the alternator and having
> problems?  Or any other combination that should be avoided?  Just to be
> careful I'm now set up so that the solar and the 110v ac charger can't be
> connected to the battery at the same time but the ideal system would be to
> have them permanently wired in.
>