Has anyone fitted an external switch to isolate their inverter? How did you do it please?

[Dark_Comet]

An inverter is drawing amps even when not in use. How often are you requiring 220 volts as1 to 2 anps can quickly drain a battery.

 

[MisterB]

Well, that one is a little odd - I don't know why it is labelled "2.4W"? That would have to be a tiny voltage for a 200A relay to make sense (If you do the maths, 200A at 12V is 2400W. Maybe "2.4W" should be "2.4KW"? or maybe they mean "24V"? I would not get that due to the confusing labelling.
As an example, this one looks identical and the writing on the relay tells you what it will do
View attachment 682152

Go for one with sensible labelling


I used to sell quite a few of these kits to camper and boat owners. Basic wiring is:

=== Heavy (power) Cable; ---- Light (control) Cable;

BAT +ve ==== FUSE ====== RELAY (PIN 30)
RELAY (PIN 87) ========== INVERTER +ve
BAT -ve =============== INVERTER -ve
BAT -ve ------------------------- RELAY (PIN 85)
RELAY PIN 30 --- fuse ---------- SWITCH IN
RELAY PIN 85 ------------------- SWITCH -ve (this is needed for the LED in the switch to work)
RELAY PIN 86 ------------------- SWITCH OUT

This method removes DC power, so it is important if you have been running the inverter on a high load and it has a fan to let it run for a while before switching off.
You could easily incorporate a countdown timer on the Pin 30/Pin 86 control circuit so when you turn the switch off there is a delay before power is disconnected to make it even easier to use if you want to ensure the fan can stay active for a while.

Hoovie

just about to wire it all up as you suggested, but realised i have the fuse AFTER the relay ....

i assumed the fuse was to protect the wiring due to the load on the wiring - does it need to protect the relay aswell? i assumed the relay would always just be left in the closed state if there was an issue?

thanks

 

[Hoovie]

Hoovie

just about to wire it all up as you suggested, but realised i have the fuse AFTER the relay ....

i assumed the fuse was to protect the wiring due to the load on the wiring - does it need to protect the relay aswell? i assumed the relay would always just be left in the closed state if there was an issue?

thanks

The Fuse should be as close to the battery as is practical, which would usually mean before the relay (as if you can fit a relay in that position, you can fit a fuse holder).
The fuse is not just to protect against an overload (the inverter itself would probably do that job anyway) but against cable damage and possible shorting to chassis. If you had cable damage and a shorting BEFORE a fuse, the only protection is the cable itself - and the kind of cable you need for an Inverter would get so hot whilst it was drawing everything the battery could give it would be an major fire hazard.

 

[pappajohn]

The on/off switch on the inverter controls the 230v OUTPUT, not the inlet.
The inverter may be drawing 100amp+ and a small switch as fitted couldn't cope with high currents like that.
The battery feed needs cutting and a HEAVY DUTY relay fitting.
The relay 12v control switch can be any kind you want, even a CBE 230v switch, and can go anywhere suitable.

 

[MisterB]

The on/off switch on the inverter controls the 230v OUTPUT, not the inlet.
The inverter may be drawing 100amp+ and a small switch as fitted couldn't cope with high currents like that.
The battery feed needs cutting and a HEAVY DUTY relay fitting.
The relay 12v control switch can go anywhere suitable.

i am fitting the relay as suggested by Hoovie and now rejigging it so the fuse holder is before the relay, i originally had it after the relay! the relay is a 12v/200A relay (ZL180 exactly as recommended)

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[MisterB]

i am fitting the relay as suggested by Hoovie and now rejigging it so the fuse holder is before the relay, i originally had it after the relay! the relay is a 12v/200A relay (ZL180 exactly as recommended)

all done and up and running, as advised. switching the relay works well, as does having a switch with an led so i can tell if the inverter is on and off - and for it to act as a reminder to turn it off when its not being used.

i have changed the battery terminal aswell from the clip on type via a terminal post to a bolt down connection, direct to the battery, as recommended in a different thread - i will at some stage fit a leisure battery isolation switch, just for peace of mind

Hoovie - thanks for your help and advice re the relay and of course, thanks to everyone else that commented/contributed !!

just need to route the wires for the switch and fix it in permanently in a prominent position.

 

[Hoovie]

all done and up and running, as advised. switching the relay works well, as does having a switch with an led so i can tell if the inverter is on and off - and for it to act as a reminder to turn it off when its not being used.

i have changed the battery terminal aswell from the clip on type via a terminal post to a bolt down connection, direct to the battery, as recommended in a different thread - i will at some stage fit a leisure battery isolation switch, just for peace of mind

Hoovie - thanks for your help and advice re the relay and of course, thanks to everyone else that commented/contributed !!

just need to route the wires for the switch and fix it in permanently in a prominent position.

Good stuff
Do remember if you have given the inverter a bit of a caning to not turn the switch off immediately when done to allow any fans to help cool the innards

 

[Raul]

When you connect a inverter, (with the switch to off), there is a massive inrush of current until caps in the inverter fill up. Many uses a resistor, or a pencil, to slow this inrush, avoid arching, then connect the inverter to the battery. I know personally that Roamer has to set sensitivity to low, as the bms detects this and cuts out, thinking it’s a short.
Now, this practice on lead acid is no worry, the lead is robust, but on lifepo4 with delicate electronics in the bms, it May suffer after many cycles of on/off.
Keep us posted as many spend money on reducing this inrush, not exercise it.

 

[MisterB]

When you connect a inverter, (with the switch to off), there is a massive inrush of current until caps in the inverter fill up. Many uses a resistor, or a pencil, to slow this inrush, avoid arching, then connect the inverter to the battery. I know personally that Roamer has to set sensitivity to low, as the bms detects this and cuts out, thinking it’s a short.
Now, this practice on lead acid is no worry, the lead is robust, but on lifepo4 with delicate electronics in the bms, it May suffer after many cycles of on/off.
Keep us posted as many spend money on reducing this inrush, not exercise it.

Thanks, I am using a Fogstar lithium battery but obviously I am keen to extend the longevity of everything, so can you advise a bit more specifically on how to resolve this, where would I fit the resistor, what sort of resistor etc I assume the led in the remote switch won't be sufficient, but can a resistor be added to the switch live which is the first "bit" to receive power once the switch has been operated or should a resistor be fitted between the relay and the positive input to the inverter to precharge it.

As the inverter already has an on off switch would it not have something already in its circuitry to ensure the safe operation?
Would the caps in the inverter 'stay full' for a period even though power has been isolated?


Hoovie
Raul
autorouter

 

[eddie]

The rule of thumb with this is to think carefully about what you want before you buy it!

Want a remote switch or the ability to turn it on and off by Bluetooth? Buy one that offers that, want a fully automatic system buy an inverter charger, connect in series with you mains hook up supply to the distribution board, unplug the converter charger and bob’s your uncle!

Most of the inverter posts either of a ‘How do I’ nature are due to buying an inverter that appears cheap, till you realise that they don’t offer the functions we all really want.

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[Raul]

Mister B, if your inverter has a built in on/off swich, is intended to be permanently connected to 12v power. This way there is no surge on switching on/off. The resistor only helps on the 12v supply when first connected. When you remove the 12v the caps empty within seconds. If you make that connection again, cycle repeats. Resistor helps you connect it to 12v and stays connected, then you use the internal or remote swich.

 

[MisterB]

The rule of thumb with this is to think carefully about what you want before you buy it!

Want a remote switch or the ability to turn it on and off by Bluetooth? Buy one that offers that, want a fully automatic system buy an inverter charger, connect in series with you mains hook up supply to the distribution board, unplug the converter charger and bob’s your uncle!

Most of the inverter posts either of a ‘How do I’ nature are due to buying an inverter that appears cheap, till you realise that they don’t offer the functions we all really want.

With lots of things in life, we think we are getting exactly what we need but then realise we can improve on what we have, so rather than scrap or replace what we have, we try to improve it.

It's not always easy to research exactly what you want/need as sometimes your needs change. I don't see that as a fault, it's part of life.

I do agree however that getting it right first time is the best option which is why I have been known to introduce 'the boss' to people as my first wife, just to keep her on her 'toes', though the downside of that is I then end up on my back, unconscious ....

 

[eddie]

My post was meant as thought provoking to others yet to buy, than criticism of people who have bought the wrong inverter already

 

[MisterB]

Mister B, if your inverter has a built in on/off swich, is intended to be permanently connected to 12v power. This way there is no surge on switching on/off. The resistor only helps on the 12v supply when first connected. When you remove the 12v the caps empty within seconds. If you make that connection again, cycle repeats. Resistor helps you connect it to 12v and stays connected, then you use the internal or remote swich.

Forgive me for being confused ... but the whole point of this thread was to be able to add a remotely sited switch (not a remote switch) to turn the inverter off and reduce current draw when it wasn't needed. I didn't want to keep lifting the seat to operate the switch on the inverter itself.the solution as advised by Hoovie meets my needs but obviously I would want to ensure that this solution doesn't create problems further down the line.
If I now need to fit a resistor if some sort in the 12v feed between the relay and the 12v positive inverter input, then I am happy to do that, I just need to know how, so any advice is more than welcome ..

How I understand it, the inverter isn't actually connected to the supply continuously (only when the relay is switched on). The inverter does have an inbuilt on off switch, but I now leave that permanently in the on position. All I am turning on or off is the 12v power to the inverter, so I assume there may still be a need for a resistor of some sort ?

 

[MisterB]

My post was meant as thought provoking to others yet to buy, than criticism of people who have bought the wrong inverter already

And that's how I took it, it's good advice as usual, thanks.

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[autorouter]

If I now need to fit a resistor if some sort in the 12v feed between the relay and the 12v positive inverter input, then I am happy to do that, I just need to know how, so any advice is more than welcome ..

How I understand it, the inverter isn't actually connected to the supply continuously (only when the relay is switched on). The inverter does have an inbuilt on off switch, but I now leave that permanently in the on position. All I am turning on or off is the 12v power to the inverter, so I assume there may still be a need for a resistor of some sort ?

As Raul says, if you are switching the high-amps 12V feed to the inverter, then a resistor to limit the inrush to the capacitors is a good idea. For a manual solution, you would need two switches, or a 2-position switch. the first position feeds 12V power through the resistor. Then a few seconds later, when the inrush has passed, switch directly to the batteries, bypassing the resistor. So one of those 'battery selector' switches rather than a battery isolator switch is what you want.

You could automate this, but you'd need two relays and some kind of time delay. It's possible to buy time-delay relays, but I think they are usually used on 240V circuits, not 12V.

If you are happy to always do a two-step switch-on, with a manual delay of a few seconds, then just using a relay with a resistor in series, plus your existing 12V relay, will work. A 2-position switch could trigger the relays as required, and it can be a standard light-duty switch because it's only switching the coil trigger currents of the relays.

 

[MisterB]

As Raul says, if you are switching the high-amps 12V feed to the inverter, then a resistor to limit the inrush to the capacitors is a good idea. For a manual solution, you would need two switches, or a 2-position switch. the first position feeds 12V power through the resistor. Then a few seconds later, when the inrush has passed, switch directly to the batteries, bypassing the resistor. So one of those 'battery selector' switches rather than a battery isolator switch is waht you want.

You could automate this, but you'd need two relays and some kind of time delay. It's possible to buy time-delay relays, but I think they are usually used on 240V circuits, not 12V.

If you are happy to always do a two-step switch-on, with a manual delay of a few seconds, then just using a relay with a resistor in series, plus your existing 12V relay, will work. A 2-position switch could trigger the relays as required, and it can be a standard light-duty switch because it's only switching the coil trigger currents of the relays.

thanks, i will try to get my head around it later - got other projects on the go, which will give me time to think it through ,,

 

[Raul]

Forgive me for being confused ... but the whole point of this thread was to be able to add a remotely sited switch (not a remote switch) to turn the inverter off and reduce current draw when it wasn't needed. I didn't want to keep lifting the seat to operate the switch on the inverter itself.the solution as advised by Hoovie meets my needs but obviously I would want to ensure that this solution doesn't create problems further down the line.
If I now need to fit a resistor if some sort in the 12v feed between the relay and the 12v positive inverter input, then I am happy to do that, I just need to know how, so any advice is more than welcome ..

How I understand it, the inverter isn't actually connected to the supply continuously (only when the relay is switched on). The inverter does have an inbuilt on off switch, but I now leave that permanently in the on position. All I am turning on or off is the 12v power to the inverter, so I assume there may still be a need for a resistor of some sort ?

With a multimeter on the pcb, you should identify the 2 posts that switches on /off. Try with inverter of, and no 12v connected; practice a combination from the existing switch until you get continuity on two posts. Remote swich, refers to remote located but still connected to the inverter by two wires. That’s what I meant. This is the easiest, cheapest to switch by a low power switch.
Once you identified the two posts that gives continuity by operating the switch, you just need to solder two wires on those posts and run the cable in your desired location. The fit any swich you like, even matching CBE line 12v will do.

 

[MisterB]

With a multimeter on the pcb, you should identify the 2 posts that switches on /off. Try with inverter of, and no 12v connected; practice a combination from the existing switch until you get continuity on two posts. Remote swich, refers to remote located but still connected to the inverter by two wires. That’s what I meant. This is the easiest, cheapest to switch by a low power switch.
Once you identified the two posts that gives continuity by operating the switch, you just need to solder two wires on those posts and run the cable in your desired location. The fit any swich you like, even matching CBE line 12v will do.

thanks, that seems way above my pay grade LOL !! i think the option that would suit my skill set is the two switch option which means i can keep what i have and add another switch - i just need to sit down and work it out, though a simple line sketch would help me a LOT, if anyone has the time to draw me the layout of what i need based on Hoovies original circuit layout?

 

[Hoovie]

As Raul says, if you are switching the high-amps 12V feed to the inverter, then a resistor to limit the inrush to the capacitors is a good idea. For a manual solution, you would need two switches, or a 2-position switch. the first position feeds 12V power through the resistor. Then a few seconds later, when the inrush has passed, switch directly to the batteries, bypassing the resistor. So one of those 'battery selector' switches rather than a battery isolator switch is what you want.

You could automate this, but you'd need two relays and some kind of time delay. It's possible to buy time-delay relays, but I think they are usually used on 240V circuits, not 12V.

If you are happy to always do a two-step switch-on, with a manual delay of a few seconds, then just using a relay with a resistor in series, plus your existing 12V relay, will work. A 2-position switch could trigger the relays as required, and it can be a standard light-duty switch because it's only switching the coil trigger currents of the relays.

This is a good 12V delay timer -https://amzn.to/3UblsRK

I use one of these to control the SSR on the Water Heater circuit so if I want to override the SOC control, I can have it run for a set time and then go off (programmable from 1 second to 99 minutes)

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[MisterB]

This is a good 12V delay timer -https://amzn.to/3UblsRK
View attachment 692486

I use one of these to control the SSR on the Water Heater circuit so if I want to override the SOC control, I can have it run for a set time and then go off (programmable from 1 second to 99 minutes)

thanks, but i would need some guidance on where and how to fit it.