Electric Gurus will this work ok ?

[iflybye]

Any Comments appreciated. Thanks

[eamarquardt]

It looks ok to me. You only need one single pole double throw relay, not two individual relays to do the switching you want. Also, one relay would be fail safe to keep the power supply and charger from ever being in the circuit at the same time. You've put a lot of thought and will have a fair amount of materials in this. However, I see no need to go to all this effort. You have the battery why not use it?

Here is a previous string on converters and battery chargers.

http://tnttt.com/viewto ... highlight=

And what I wrote:

I looked at the web site for one of the converters recommended. Seems like they are pretty expensive. I owned a boat for years and had a marine battery charger that would keep 4 batteries properly charged at dockside and allowed use with the charger connected and powered up.

I don't see any need for a converter that can power 20 or more amps when you have a good deep cycle battery in the circuit. You (or at least me) rarely use the full capacity of these units. A 10 amp charger and with the battery in the circuit to handle those short periods of time when you do need a bit more power always worked for me on the boat. In fact, although I had three batteries on the boat, my pattern was to only keep one "on line" while away from the dock. The other two were for EMERGENCIES only (a wise habit when you can't hand crank or push start your diesel engine, IMHO). I sometimes went for a two or three days at a time only running the engine for about 20 minutes in the evening to generate enough hot water (the hot water was created using a heat exchanger from the cooling system on the engine) for showers! If you keep it simple (we only used a few lights, occasionally the VHF radio, no appliances save the on demand water pump, the solenoid for the propane (a safety feature on a boat), and in those days a small crt TV and vhs player) and NEVER fully discharged the one battery that I had switched into the main power bus.

I'd recommend a marine charger (good ones that will multi stage charge 2 separate batteries are about a hundred bucks) that can keep your batteries up at home and in a campground with a/c. Of course a good solar panel will keep your battery up when a/c is not available but might not provide enough power (depending upon the size of your panel and how many amp hours you use each day) for extended use (week or maybe more) but would probably keep you going for several days before your battery would be discharged and by then you'd probably have your trailer connected to your tow vehicle and charging the battery on the go anyway.

In short, if you keep it simple, don't try to run fans for extended periods (or heaters or a/c units) a 100 amp hour battery and 5 or 6 amps of charging current for a few hours each day would work just fine (IMHO and based upon my experince with a cruising sailboat).

There you have it (again), the world according to Gus.

Cheers,

Gus

[Dale M.]

I see Gus's point about a SPDT relay and concur that is all you need and it also prevents both "power" sources from being connected simultaneously .. Sort of a fail safe.....

What I don't see is when manual toggle switch is to "right" position that there is any continuity there to complete an circuit.... BUT that may be a technicality as the drawing may done wrong to show contact arrangement....

Also.. This may help your design skills for contact arrangement...





Also here....
http://www.6066gmcguy.org/BoschRelay.htm


Also I would rather see it sketched as the "common" terminal (30) to trailer lighting/plugs (12 volt circuits) and terminal 87a to battery (12 volts) and terminal 87 to AC/DC converter/inverter supply (12 volts).... This gives you your fail safe... And by using the output of DC converter through control switch to relay, if switch is left ON all the time it will automatically go into "switched to converter" power each time you power up converter (connect to shore power)

So with control switch NOT operated you are on battery and with control switch operated you are on AC/DC supply(when available).... Also you don't waste any battery power to keeping relay operated when you do not have shore power...

Dale