Relay between 12V source and Inverter

[NorthernSands]

Hi all,

Can anyone think of a reason why fitting a relay to the 12V feed of an inverter, to allow remote turn off via a dash switch, would not be a good idea?

This particular inverter does not have a remote control of any sort, but I don't want to have to find the little on off switch on the unit itself.

Many thanks!

Peter.

 

[PhilandMena]

I think the extra wiring is going to be a RPITA and in the final solution will result in extra cost and you still having to flick a switch.

 

[NorthernSands]

I think the extra wiring is going to be a RPITA and in the final solution will result in extra cost and you still having to flick a switch.

I really don't mind the wiring as the inverter will be close to the front of the van, near the EBL. I've already had the dash off once recently, and happy to do it again. I have relays to control the stereo switched 12v and power to the USB-C charger to fit. I could piggy back it on there, I guess...

 

[Lenny HB]

I fitted a battery isolation switch in the 12v feed to my inverter.

 

[Mark McG]

Interested to learn the size of relay required - Some big inverters out there

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[Lenny HB]

Didn't read the question properly as well as the switch I fitted a 100 amp relay (1000 w inverter) that I can switch from inside the van.

 

[NorthernSands]

I fitted a battery isolation switch in the 12v feed to my inverter.

Effectively doing what I want. So you don't think there'll be any harm to the inverter, or it's devices, by just cutting the source feed?

Didn't read the question properly as well as the switch I fitted a 100 amp relay (1000 w inverter) that I can switch from inside the van.

Ah. Yes, perfect, this is what I'd like to do.

Interested to learn the size of relay required - Some big inverters out there

A basic relay can be up to 20 to 30 AMPs. My inverter is only 300w, so I just need to account for that: ~25amps, and it'll only be used for charging devices (laptop: 65w, tablet: 36w, phone: 18w).

 

[dunnah01]

Effectively doing what I want. So you don't think there'll be any harm to the inverter, or it's devices, by just cutting the source feed?


Ah. Yes, perfect, this is what I'd like to do.


A basic relay can be up to 20 to 30 AMPs. My inverter is only 300w, so I just need to account for that: ~25amps, and it'll only be used for charging devices (laptop: 65w, tablet: 36w, phone: 18w).

He peak power is typically double the inverter power so the relay should probably be capable of at least 600 watts / 50 amps

 

[NorthernSands]

He peak power is typically double the inverter power so the relay should probably be capable of at least 600 watts / 50 amps

Good shout. I'll bear that in mind.

 

[Lenny HB]

A basic relay can be up to 20 to 30 AMPs. My inverter is only 300w, so I just need to account for that: ~25amps, and it'll only be used for charging devices (laptop: 65w, tablet: 36w, phone: 18w).

If that is all you are using it for it's better to buy 12v chargers/power supplies, more efficient than using an inverter.
We only use our inverter for charging the e-bikes & the washing machine everything else is 12v powered.

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[NorthernSands]

If that is all you are using it for it's better to buy 12v chargers/power supplies, more efficient than using an inverter.
We only use our inverter for charging the e-bikes & the washing machine everything else is 12v powered.

It's for convenience as well. The best 12v USB-C PD charger I've found can only get to ~18w, whereas I'll need closer to 65w if actually using my laptop at the time. It will charge off 18w when off, but that's not useful.

 

[DBK]

Effectively doing what I want. So you don't think there'll be any harm to the inverter, or it's devices, by just cutting the source feed?

I turn mine on and off by switching the 12 volt supply. I can't readily get at it so the switch on the front of the inverter is permanently on. It hasn't done any harm so far but whether this applies to every inverter I can't say.

 

[NorthernSands]

I turn mine on and off by switching the 12 volt supply. I can't readily get at it so the switch on the front of the inverter is permanently on. It hasn't done any harm so far but whether this applies to every inverter I can't say.

Thanks. I'm of the opinion that devices should be able to cope with sudden loss of power, I just don't know how an inverter handles it as they have capacitors and so on that hold charge for a wee while.

I reckon I'm worrying too much and should just do it.

 

[DBK]

Thanks. I'm of the opinion that devices should be able to cope with sudden loss of power, I just don't know how an inverter handles it as they have capacitors and so on that hold charge for a wee while.

I reckon I'm worrying too much and should just do it.

It can only go up in smoke but I doubt it will. When I turn mine off it whines quietly to itself which fades away after a few seconds as the capacitors discharge. BUT I never start or turn it off under load. This could damage whatever it is connected to. The hairdryer would be fine but more delicate things might suffer.

 

[Lenny HB]

It's for convenience as well. The best 12v USB-C PD charger I've found can only get to ~18w, whereas I'll need closer to 65w if actually using my laptop at the time. It will charge off 18w when off, but that's not useful.

You can get dedicated laptop 12v chargers that charge at the same rate as the mains charger.

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[two]

Same for some e-bikes

 

[NorthernSands]

You can get dedicated laptop 12v chargers that charge at the same rate as the mains charger.

I've not seen one that is for USB-C (though I'm sure they exist), and it would also mean putting the cigar lighter back in. I'd also have to re-wire it to come off the leisure battery (the solar charger only trickle chargers the starter battery). And having mains power is handy. There's also our Audio Pro T3 that would need charging occasionally (figure-8 mains lead at 40w). And toothbrushes.

 

[tonyidle]

Good shout. I'll bear that in mind.

That would only be important if you turn off the inverter when it is operating under load. You would expect to turn off anything using the inverter output before turning off the inverter.

 

[Lenny HB]

I've not seen one that is for USB-C (though I'm sure they exist), and it would also mean putting the cigar lighter back in. I'd also have to re-wire it to come off the leisure battery (the solar charger only trickle chargers the starter battery). And having mains power is handy. There's also our Audio Pro T3 that would need charging occasionally (figure-8 mains lead at 40w). And toothbrushes.

Toothbrushes you need a good quality pure sine wave inverter or they blow up. The boss has a Bosch toothbrush we use a USB charger for it about cost a fiver.
What's the PC?

 

[NorthernSands]

Toothbrushes you need a good quality pure sine wave inverter or they blow up. The boss has a Bosch toothbrush we use a USB charger for it about cost a fiver.
What's the PC?

It is a Pure Sine Wave inverter (300w from Photonic Universe, if that means anything). Laptop is a Lenovo X380. Not too power hungry but needs a min of 65w when being used. It can either take USB-C or thin yellow tipped rectangular charger. I tend to use the USB-C charger as that also chargers by tablet and phone.

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[Reallyretired]

You will have no problem using an ordinary 40A automotive relay to switch an inverter of that size. I have a 500w one which I've used for some years with that arrangement, no problem.

The little switch on the inverter doesn't actually cut of the 12v supply and is only a very low rating. An alternative which I have done in the past is to open up the inverter, solder a couple of wires to the back of the switch, wires can be quite long, and just fit a suitable switch remotely. The switch on the inverter is left in the off position of course.

 

[Lenny HB]

It is a Pure Sine Wave inverter (300w from Photonic Universe, if that means anything). Laptop is a Lenovo X380. Not too power hungry but needs a min of 65w when being used. It can either take USB-C or thin yellow tipped rectangular charger. I tend to use the USB-C charger as that also chargers by tablet and phone.

Some 12V chargers here.

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[NorthernSands]

Some 12V chargers here.

Lenovo ThinkPad X380 Yoga Charger *Replacement Lenovo ThinkPad X380 Yoga Power Adapter Best Buy in UK

Brand new Lenovo ThinkPad X380 Yoga charger best buy in www.laptoppowercharger.co.uk, replacement laptop AC adapter power supply for Lenovo ThinkPad X380 Yoga.

www.laptoppowercharger.co.uk

Yeah, but thintip so can't use it on my phone nor tablet, and I'd have to remove the USB-C charger I have instead of the cigar lighter, then rewire it to the hab battery. Still wouldn't be able to charge the speaker. All to save conversion inefficiencies (which I get, but how much saving will it give me in the real world?). I'd have fewer chargers and more flexibility by using the inverter.