External low voltage relay to shut down mobile inverter.

[Mattb4]

What I am attempting to do is to shut off a mobile inverter at my adjustable battery low voltage point rather than the inverters factory set limit. I see that I can buy a DC Digital Low protection switch on Amazon that would work with a DC control AC relay to shut off a AC device from the inverter but I am not sure how to arrange to shut the inverter down. This would be desirable to limit battery draw.

The remote on/off switch for this class of inverters seems to just be a momentary signal that the inverter turns off or on depending on the state of inverter.. So from the output of the low voltage switch how would I go about doing this? Thanks for any feedback.

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[time2roll]

I would be inclined to cut output power with a relay and let the inverter idle. BMS could easily switch off the low idle DC power if there was no charging for an extended period.

 

[Mattb4]

I would not be using lithium batteries. So no BMS. Might have to see if I can figure out which wires on the 8 conductor remote phone cable passes the on/off signal.

 

[Texas-Mark]

I see that I can buy a DC Digital Low protection switch on Amazon that would work with a DC control AC relay to shut off a AC device from the inverter but I am not sure how to arrange to shut the inverter down.

Does the inverter have a rocker switch? I use a 12V low voltage cut-off that has a NC relay, in parallel with the inverter switch (that is left off). Works great.

 

[Mattb4]

One inverter I have does have a rocker switch so that is a good thought. It is a 1000w 12v model and not the 2000w 24v one I was thinking of using but it should handle the load. (200w).

 

[Vigo]

I would just intercept your on/off switch with the relay, unless it really is a momentary switch as you said in which case i'd have to think about it a little harder.

I have a 5kw MSW 12v inverter, it is just as big and heavy as my 5kw Growatts, but unlike the Growatts the idle consumption is about 6w if i remember correctly. So make sure your inverter actually has an objectionable idle draw before going down any rabbit holes. Switching off the AC output side might accomplish basically the same thing but with less head scratching.

 

[Mattb4]

Already wired up my 12v inverter to turn on or off with wires fed through small holes in the side of the inverter. Should be getting in my low voltage cut off switch and DC relay today.

 

[Mattb4]

Got it in and installed. Seems to work but I will not know for sure until the battery drops to low voltage cut out.

 

[Mattb4]

Unfortunately the solid state relay I bought does not act as I wanted to break/make the circuit for on and off operation of the inverter. I need to find a different DC powered contact NO device.

ETA: I think my problem was using a DC to AC relay. After testing the external switch wires I find that I have a 12vDc circuit through the switch which means I should have used a DC to DC relay.

 

[Vigo]

Simple fix, then. Any 5-terminal automotive relay will have an NO terminal. It's usually labeled 87a although if it's not, there might be a diagram on the side of the housing saying which it is.

 

[Texas-Mark]

Why are you not just using the relay on the low voltage cut-off board? The rocker switch on the inverter is typically only going to be a low voltage/low current signal switch.

 

[Mattb4]

Why are you not just using the relay on the low voltage cut-off board? The rocker switch on the inverter is typically only going to be a low voltage/low current signal switch.

The low voltage cutoff board supplies battery power through it. My initial thinking was the inverter switch was simply a dry contact type of connection so I was concerned about injecting a voltage/current around the switch. It is possible that your suggestion would work but I think I prefer the isolation of a non powered open and close relay contact to make the circuit.

 

[pollenface]

The most robust LVD device I have found is the programmable load terminals on good quality charge controller. A 60v 10a Epever tracer Mppt costs about $68aud and can be used solely as a programmable Low/over voltage disconnect/reconnect device at the cost of a few extra mA of parasitic load.

I've tried various gadgets from ebay/amazon including a few like in the photo above with limited reliability.

 

[Mattb4]

The most robust LVD device I have found is the programmable load terminals on good quality charge controller. A 60v 10a Epever tracer Mppt costs about $68aud and can be used solely as a programmable Low/over voltage disconnect/reconnect device.

I've tried various gadgets from ebay/amazon including a few like in the photo above with limited reliability.

The 30a Make Sky Blue charge controller I have does not have programmable load low voltage set points.

 

[pollenface]

The 30a Make Sky Blue charge controller I have does not have programmable load low voltage set points.

That is irrelevant.

My suggestion is that for $68aud you can have a robust low/over voltage disconnect/reconnect device.

 

[Mattb4]

I was partly wrong about the MSB SCC. It does indeed have a low voltage cut off to the load terminals that can be set. However it has no differential range (turn off and do not turn back on until higher voltage). That would cause short cycling.

I see no point in spending money on a new SCC just to get the low voltage cutoff like you mention. But I appreciate the advice.

 

[Texas-Mark]

The low voltage cutoff board supplies battery power through it. My initial thinking was the inverter switch was simply a dry contact type of connection so I was concerned about injecting a voltage/current around the switch. It is possible that your suggestion would work but I think I prefer the isolation of a non powered open and close relay contact to make the circuit.

Ok. I though the relay was just a dry contact relay. Can probably just use any 12V relay. Does not have to carry any significant current.

 

[pollenface]

I see no point in spending money on a new SCC just to get the low voltage cutoff like you mention. But I appreciate the advice.

I'm not suggesting you replace your current SCC.

As for the Epever 1206an, it's just functions an adjustable voltage sensing switch with no panels connected to it. I wasted too much money on other products out there hoping for the same result. Good luck