How to shut off converter when sun is shining?

[Joe McPlumber]

Apologies but either there are few people in my particular circumstance or i'm too dumb to ask Google the right question.

I live in a large travel trailer. I have 400 watt solar array and six large storage batteries so i rarely need mains power, except for the fridge which i intend to put on an inverter eventually. But my converter is of the old fashioned single-stage stupid variety and it wants to keep buzzing away regardless of my needs. It's wasting power, vibrating my nervous system at 60hz, and probably cooking my batteries.

I've presently got a manual switch on it, as well as a timer to turn it off at daybreak and back on at night. But this is obviously no help if it rains for a week or i use an unusual amount of power.

I think i just want to turn on the converter if battery voltage falls below a certain threshold. I can build a DIY circuit if someone can point me to one but i'd prefer something off the shelf if it doesn't cost too much. I'm clever enough with electrical/electronc stuff to follow instructions and build things but i'm not an engineer.

Also it'd be nice if i could take the output from the converter and run it through a better charging circuit, so as to protect my batteries. But Google will only tell me about converters that already do 3 stage charging or are configured for add-on modules. I do not wish to buy a new converter. I do have a spare PWM controller, might it be as simple as hooking that to converter output?

TIA for any advice.

[Mike90250]

First, if you want to purchase a 3 stage charge controller for proper/better charging of your batteries, your need to feed it about 19V. Some voltage gets "lost" in the controller, and to properly charge batteries in chilly weather, you need about 15V
So adding something to your existing converter (apparently a DC power supply ) is not really going to work because the headroom voltage does not exist.

I suppose you can add a "dump load" so that when your battery is full, the dump load kicks in and starts heating up a big resistor. That resistor needs to be sized to the amperage of the power supply, so until that is known, that option goes nowhere.

What I suspect you have is a dumb 30A power supply set to 14V and it likely does well enough for most of the RV's out there. Do you have unusually heavy or light loads that you need to accommodate ? How often do you have to be adding water to the batteries ?

[NCmountainsOffgrid]

I'm confused, are you plugged into SHORE POWER? If not, what is the NEED for the Converter in the first place?
Converters change 120v shore power to 12v power for the majority of your RV power needs, since you obviously don't have any appliances or needs for 120v power, otherwise, at least unless you are needing air conditioning, which would require Shore Power anyway.
Converters also can have built-in Battery Chargers, but that's only applicable if you are plugged into Shore Power, or have an onboard Generator for 120v supply.

Having a solar array is great, but is it not simply wired directly to your Battery Bank, charging the batteries when the sun is shining? If so, your batteries are already taking care of powering all of your 12v RV needs, with no converter needed.

Now, do you for some reason have your solar output wired to your CONVERTER? if so, WHY?
With a solar array providing Battery Charging, and the battery bank providing your 12v output needs, the Converter then is not part of the required power equation.

NC Mountains Class A Diesel Pusher, 100,000 miles since 2014

[ewarnerusa]

I second what NCmountainsOffgrid said, if you're offgrid without any shore/generator power then the converter has nothing to do and is not energized. At least it shouldn't be, unless you're supplying 120V AC power via an inverter which is providing a power source to your converter. If you're in that situation, then you do indeed want a switch for turning the converter off. What I did is wire my converter power supply into its own AC breaker in the breaker panel. I use the breaker as the on/off switch and it is nearly always in the off position.

[Joe McPlumber]

I'm not off grid entirely, as stated i still run my refrigerator on AC and occasionally i run an electric heater and/or an Xbox and television. I don't have that much capacity as yet. So the solar panels mostly provide my lighting and other low voltage needs for now.

I'm sorry if i've confused anyone but that's exactly why i'm here. I don't seem to fit into the usual expectations as i'm neither off grid nor is my solar system grid tied; it's just there to provide what i can get out of it.

Problem remains, if the sun doesn't shine for multiple days or if i use an excess of power, the batteries will be drawn down. *Something* needs to charge them back up?

Edit: i'm attaching a diagram. Sorry i'm not very good at drawing but it's basically a standard RV only with solar panels and extra batteries.1_diagram.jpg

[NCmountainsOffgrid]

I guess, though, that I'm still confused.... what do you mean by " i still run my refrigerator on AC and occasionally i run an electric heater and/or an Xbox and television." ... is this by being PLUGGED INTO shore power, or by being plugged into a GENERATOR???
If so, is the shore power ALWAYS available? or, are you just running a generator 'as needed'? If you have a residential 120v fridge, I suppose the answer to the question is that you MUST be on shore power.

If you are then on shore power, WHY(?) would you need Solar POwer????

also, I'm not sure your Battery Bank powers your Converter, but just the opposite...and your Battery Bank goes to your FUSE panel, to power all 12v items. Only the incoming SHORE POWER/Generator Power provides any power thru your Converter, since that's the only time it's needed - to power your 12v lights, fans, etc, and to charge the Battery Bank.

[Joe McPlumber]

Maybe it saves me money since it serves most of my power requirements. Maybe i'm building incrementally because i'm not wealthy, and i plan to put fridge on an inverter later. Perhaps i like being self-sufficient as possible. Maybe i'm paranoid and preparing for SHTF. Heck maybe i just find it amusing when the wind blows out the mains power but i'm completely unaffected. What's any this got to do with what i asked?

Most of the time the converter is unnecessary. It supplies 12v and recharges the batteries when solar is insufficient, such as occurs if it's stormy for an extended period. Since i do not wish to watch the meters all the time and babysit a switch, i wondered if someone might know how to switch it automatically when needed.

[SunEagle]

Maybe instead of a converter you just get a quality battery charger which can be power from your AC Grid and will charge the batteries without cooking them.

[jflorey2]

If you are then on shore power, WHY(?) would you need Solar POwer?

Because his charger is noisy and he doesn't like the noise.

Simple/cheap options include:
-Comparator plus relay to turn off charger at 14 volts and on at 12 volts
-Relay with small solar panel to turn power off during sun hours

[Joe McPlumber]

-Comparator plus relay to turn off charger at 14 volts and on at 12 volts

Thanks very much, that sounds like what i want and will make my googling easier, since i didn't know what to call what i wanted.

My controller has a "load" output that doesn't output when the sun goes away and i was thinkng to hook that to a relay but, it wouldn't be much different than the timer that's on it now.

Anyhow thanks again.