Grid tie and battery together

[SunEagle]

I will keep an eye on it and report back. The good thing about this particular relay is it has two sets of terminals so if one side goes kaput maybe the other will still work unless the coil part gives up!!

OK. Maybe you should look into a sturdier relay in case this one fails quickly. I really want to see you succeed in this test.

[Tired sparky]

I’m hoping these sort of components have s bit of wiggle room on their specifications? Most things in the electrical industry are for safety.

[Tired sparky]

I will keep an eye on it and report back. The good thing about this particular relay is it has two sets of terminals so if one side goes kaput maybe the other will still work unless the coil part gives up!!

[SunEagle]

Just looked again at the relay specs, 24 volts coil and 30 amps @ 28 volts contacts.

With only 28V you may exceed the arc rating and lose those contacts pretty quickly.

[SunEagle]

I have a 2S2P panel setup. Four 160 watt Panels with a Vmp I think of 18 volts? Under load I should be running something like 30 odd Volts through the relay?

Then you are probably ok and the relay can handle that voltage during an interrupt. But again each time you open those contacts you can create an arc which will degrade the contacts over time. Please keep an eye on them.

[Tired sparky]

Just looked again at the relay specs, 24 volts coil and 30 amps @ 28 volts contacts.

[Tired sparky]

I have a 2S2P panel setup. Four 160 watt Panels with a Vmp I think of 18 volts? Under load I should be running something like 30 odd Volts through the relay?

[SunEagle]

At the moment I’m only putting about 16 amps max through the relay. I plan to double my panels eventually but even then due to placement issues I doubt I will ever get much more than 20 amps at any one time?

It is not only the amps but the voltage that you are interrupting. What is the relay rated? The amp rating of contacts is when they are closed and touching each other. If you open them under load then an arc can be created which can cause damage to the relay.

[SunEagle]

Well, if that happens, let's hope the OP gets back to us with feedback so that the readers can benefit. I would hope he would use a relay rated for DC and the Amperage of that circuit. At high Amps there are contractors that can handle hundreds of DC Amps.

You are correct. There are quality contactors that can interrupted high DC voltage and are designed with arc shoots to minimize their affect. But based on what Tired Sparky is posting the relay is a cheap amazon unit that could easily fail and cause more then just smoke.

[Tired sparky]

At the moment I’m only putting about 16 amps max through the relay. I plan to double my panels eventually but even then due to placement issues I doubt I will ever get much more than 20 amps at any one time?

[SunEagle]

The relay is DC rated at 24 volts. Looking again the amperage has 40 in the title but in the info section 30A at 28 volts?? It has Two separate ‘gangs’ for switching two sets of loads, I’m using only one of the gangs.

Im UK based if anyone didn’t know. I got my relay from Amazon.co.uk but they are also on Amazon.com as I just checked. If you put...... taiss jqx 12f 2z .......in the search it comes up the same unit. $15 if it blows up so no biggie. It’s been running since I last posted maybe a month ago? Has about a dozen switch cycles so far.

Can you post post pics here?

What voltage are you interrupting? Is that 24V the coil rating or the contact rating? Most of the high voltage relays have a DC rating of 300V. Since your are disconnecting a string of panels from the battery CC to the grid tie inverter I would think the voltage could be pretty high. But if you have selected a minimum number of panels and their Vmp is lower then the contact rating on the relay you should be ok.

[Tired sparky]

The relay is DC rated at 24 volts. Looking again the amperage has 40 in the title but in the info section 30A at 28 volts?? It has Two separate ‘gangs’ for switching two sets of loads, I’m using only one of the gangs.

Im UK based if anyone didn’t know. I got my relay from Amazon.co.uk but they are also on Amazon.com as I just checked. If you put...... taiss jqx 12f 2z .......in the search it comes up the same unit. $15 if it blows up so no biggie. It’s been running since I last posted maybe a month ago? Has about a dozen switch cycles so far.

Can you post post pics here?

[Ampster]

Well, if that happens, let's hope the OP gets back to us with feedback so that the readers can benefit. I would hope he would use a relay rated for DC and the Amperage of that circuit. At high Amps there are contractors that can handle hundreds of DC Amps.

[SunEagle]

Is that a safety issue or are you just having a bad day? Most relays I know of have a MTBF significantly longer than 60 times. Relays have been around a long time and actually performed logic functions before computers. I am sure there are ways to abuse a relay but assuming it is matched to the voltage and amperage of the circuit it should last some time. In this case it was two poles at 40 Amps for each pole. What am I missing?

It all depends on the type of contacts used in the relay and the voltage it is interrupting. Some relays are not designed to interrupt DC voltage and tend to Arc causing the contacts to fail.

If that relay is a solid state type then the life span and cycle count go way up compared to a mechanical relay that is being abused.

IMO I think the OP is really not thinking this through but if it works for them then great.

[Ampster]

Hmm. I give it a couple of months before that 24V relay fails. But if it works for you then have at it.

Is that a safety issue or are you just having a bad day? Most relays I know of have a MTBF significantly longer than 60 times. Relays have been around a long time and actually performed logic functions before computers. I am sure there are ways to abuse a relay but assuming it is matched to the voltage and amperage of the circuit it should last some time. In this case it was two poles at 40 Amps for each pole. What am I missing?