Automotive relays would be used for 12V. But can I do that? Can I put 120VAC through a relay usually used for 12VDC?

The power input to the inverter IS 12V!
12V from your 12V power supply powers the coil.

 

hi,
What do you think will happen to the relay coil if you do that.?
E

I don't know. I would think it might help the relay release some of the smoke trapped inside it?
I was talking about the switch side of the relay. Could I use an automotive relay with a 12V coil to control a 120VAC circuit?

 

hi,
Post a link or a datasheet for the 12V relay you are considering.
E

 

I was talking about the switch side of the relay. Could I use an automotive relay with a 12V coil to control a 120VAC circuit?

No, automotive relays switch automotive voltages: 12V

hi,
Post a link or a datasheet for the 12V relay you are considering.
E

I was recommending
https://uk.rs-online.com/web/p/non-latching-relays/4881954
to switch between the 120V AC from the mains and the 120V from the inverter
and
https://uk.rs-online.com/web/p/non-latching-relays/6995960
to switch the power to the inverter

 

hi P,
Did you read the product details in Ian's link.?

Product Details
MY Series

Switch power: 10A version: 1100W, 5A version 660W
Contact resistance: 100mΩ
Isolation coil to contact: 2000Vac
Operating temperature range: -55 to +70°C
Maximum switching voltage: 250Vac; 125Vdc
Contact material: AgNi
Dimensions: H42.4mm x W21.5mm x D28mm

And


Specifications

Attribute	Value
Coil Voltage	12V dc
Coil Power	1.4W
Coil Resistance	103 Ω
Isolation Coil To Contact	500V rms
Contact Configuration	SPDT
Mounting Type	Panel Mount
Switching Current	40A
Terminal Type	Quick Connect
Maximum Switching Voltage DC	14V dc
Depth	26mm
Height	25mm
Length	22mm

 

hi,
Post a link or a datasheet for the 12V relay you are considering.
E

I

hi,
Post a link or a datasheet for the 12V relay you are considering.
E

I was not considering using auto relays, someone else in this thread suggested using auto relays.
But now that I think of it, he must have meant to use the relays to control the inverter 12V input from the battery, not the 120V output to the fridge.

Never the less, I already have these relays laying around: https://www.amazon.ca/gp/aw/d/B08J3VNJMB?psc=1&ref=ppx_pop_mob_b_asin_title

The fridge is 120VAC and 1.5A (165W I think). Could I use the relays above to control the power to the fridge?

 

hi P,
Did you read the product details in Ian's link.?

Product Details
MY Series

Switch power: 10A version: 1100W, 5A version 660W
Contact resistance: 100mΩ
Isolation coil to contact: 2000Vac
Operating temperature range: -55 to +70°C
Maximum switching voltage: 250Vac; 125Vdc
Contact material: AgNi
Dimensions: H42.4mm x W21.5mm x D28mm

And


Specifications

Attribute	Value
Coil Voltage	12V dc
Coil Power	1.4W
Coil Resistance	103 Ω
Isolation Coil To Contact	500V rms
Contact Configuration	SPDT
Mounting Type	Panel Mount
Switching Current	40A
Terminal Type	Quick Connect
Maximum Switching Voltage DC	14V dc
Depth	26mm
Height	25mm
Length	22mm

I actually originally dismissed it because I thought it was a latching relay. Now I see it's a non-latching one.
I'll look into it.

 

Anyways. I want to thank you all for your responses. I learned just enough to be dangerous!
I also know I missed a few posts. Off to read them. Thanx again to all for your help.

 

Hey guys.
I bought these thinking they were 12V switches: https://www.amazon.ca/gp/aw/d/B07QNY5STC?psc=1&ref=ppx_pop_mob_b_asin_title&th=1

Description says nothing about using DC power. I just read the boat switch tittle and mistakenly thought that's be for 12V stuff.
Are they safe to use with 12VDC? And if so, what sort of amperage would I be able to safely put throught them?

 

Hey guys.
I bought these thinking they were 12V switches: https://www.amazon.ca/gp/aw/d/B07QNY5STC?psc=1&ref=ppx_pop_mob_b_asin_title&th=1

Description says nothing about using DC power. I just read the boat switch tittle and mistakenly thought that's be for 12V stuff.
Are they safe to use with 12VDC? And if so, what sort of amperage would I be able to safely put throught them?

 

I'm not deliberately trying to be confusing (I can be confusing without even trying).
I wasn't sure if the TS had a 12V power supply, or whether it was a 12V battery charger

Not accusing anyone of anything. For sure, we could use a clearer picture of what the TS is doing - or trying to accomplish.

Also relays typically have a lower voltage signal to control a higher voltage switch.

Not necessarily. While it is more common to use a low voltage to trigger a higher voltage, sometimes the opposite is true. You CAN use the presence of a high voltage at a low current to switch a low voltage high amperage device.

Why is using the mains power as a signal the better way to go about it?

Not specifically necessary that way. If you power a power supply from mains you can use that lower voltage to switch in an inverter. It's just a matter of choice. My way of thinking on this is that if the power supply fails while mains are still present you will switch to battery operation when you don't need to. And a mechanical relay (analog as you called it) means it's impossible for the NC and the NO contacts to be active at the same time. One MUST break before the other can MAKE (contact).

Automotive relays would be used for 12V. But can I do that? Can I put 120VAC through a relay usually used for 12VDC?

Automotive relays are designed for DC circuitry. That's their intent. Switching an AC voltage can cause arcing that the contacts were not designed to handle; and that can lead to a very short lifespan of the contacts. Also, the spacing of the metallic materials and any insulation between them has to be considered. Just because a relay can handle high current doesn't mean it can handle high voltage. At some point the voltage can arc across the two nearest points of metallic structure and cause issues.

If you look at relays and their ratings you'll see that they are often rated to handle higher current at AC voltages whereas they are often much lower current rated for DC voltages.

 

Says "Use for Car Auto Boat". However, I would not ask more than 7 amps through the contacts if using it to switch DC voltages. However, the "Center Off" feature (DPDT ON-OFF-ON) can be useful.

 

View attachment 243984
Says "Use for Car Auto Boat". However, I would not ask more than 7 amps through the contacts if using it to switch DC voltages. However, the "Center Off" feature (DPDT ON-OFF-ON) can be useful.

That's good to know. I have some automotive relays I can use if I need to go over 7A. In fact most of the stuff won't really ho over 2 or 3A. So I'll slap on a relay if I go over 2A.

Is 7A just a guess of yours or a gut feeling? Or is there some math to it?

 

Also depends on the type of DC load, inductive or resistive, Inductive load, de-rate lower .