Combining 110v & 12v charging systems

[mmccoy]

I''m looking to add a solar panel/controller to my boat. I already have a Xantrex Trace 20 110v (shorepower) charger.

Everything I read discusses how to hook up 110v charging or 12v charging but not both together.

The question is, how do you add another charger circuit (of a different voltage) to an existing system?

[SCSeaside]

Hi mmcoy,
Your 110v shore power charger converts the 110v AC to a charging current of 12-14 volts DC. Once the shore power is unplugged, the charging stops and your solar panel can kick in to trickle charge your batteries. If your solar panel doesn''t already have an isolating circuit, you can isolate your solar panel from your shore power by simply installing a diode in-line between your solar panel and the battery. This will limit current flow to one direction only. Many panels already have this protection built-in and a quick check of the manufacturer''s specs should tell your whether yours does or not. Hope this helps.

[GordMay]

A solar Panel puts out an unregulated charge, so long as there is sunlight, regardless of battery voltage (state of charge). A Solar Charge Controller could provide "Regulated" output.
Your Xantrax 110V Battery Charger senses the battery voltage, and varies it’s output accordingly (so long as 110V is applied).
Hence, you don’t want your Solar Panels connected at the same time as your AC Charger - the Voltage output from the Solar Panel would “fool” the AC Charger, and reduce it’s output.
Put a disconnect switch in series with the positive output of the Solar Panel (& Blocking Diode, if equipped).

[mmccoy]

Ahh... I just knew you couldn''t simultaneously connect the solar panels/controller to the batts with a 110v charger wired to the batts as well without one charger ''interfering'' with the other.

Makes sense to disconnect the solar charging circuit when attached to shore power (and using the Xantrex).

It''s a shame to ''waste'' the power being generated by the solar panel(s) even when connected to shore power though. hmmm... maybe in addition to the disconnect I could have an extra switch position that would shunt it to a seperate, dedicated 12v outlet as well.

[bobsquarepants]

How about diode isolation?

Ed

[GordMay]

Your (proposed) “dedicated” 12V outlet wouldn’t need to be shunt switched - just connect it in parallel with the Blocking Diode (Ed’s “isolation”) ahead of the disconnect (which is effectively, a permanent “shunt” connection). The outlet will always get it’s power from the Solar Cell, but will only be able to power devices rated less than the Solar output.
This is tough to put into words, when a very simple sketch would be so illuminating. Have I made it clear as mud?
Gord