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Please help me learn why this happened so I don’t do it again!!

terry82517

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Apr 27, 2020
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Hello all, I have a isolator switch between my panels (2x 160w) and my Victron 100/30 mppt controller.

Today I wanted to do some work on the panels so I turned the isolator switch off. As I did, there was a small pop sound and a small amount of smoke started to come from the bottom of the mppt.
Now the mppt isn’t showing any amp output.

Does anyone know why this would happen.
I think I must have blown a internal fuse in the mppt?
 
When the switch let go of the connection it didn’t do it smoothly. It had a fragmented release that made a fragmented arc and it dumped constipated electrons.

Replace the fuse but I think you killed it
 
When the switch let go of the connection it didn’t do it smoothly. It had a fragmented release that made a fragmented arc and it dumped constipated electrons.

Replace the fuse but I think you killed it
Ah great explanation Thankyou.

yeah I think the mppt is toast as I don’t think they are repairable.

would a higher quality switch “let go” more smoothly so this doesn’t happen again?
 
I have one of these between my panels and SCC:

and one of these between my SCC and battery positive busbar:

The amp ratings are for my system and components, and are higher than you require, but you can get similar items at your ratings. The important thing is that they are from Blue Sea, Cooper/Bussman, or some similarly reputable brand. There are tons of junk lookalikes on Amazon and elsewhere that are nowhere near the same quality. My SCC is a Victron 250 | 100, and has been connected and disconnected many times from the panels without issue. I hope this is helpful to you!
 
No matter how poor the switch I cannot see a few 10s of volts and amps from a current limited source causing damage with intermittent connection to the input, ( this is assuming there was a battery connected to the output).

There is an internal fuse and a forum member opened up the case and replaced the fuse on a Victron Controller

Victron products have a 5 year warranty, I suggest you take advantage of this.

Mike
 
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No matter how poor the switch I cannot see a few 10s of volts and amps causing damage with intermittent connection to the input, ( this is assuming there was a battery connected to the input).

I agree. The max amount of current the panels supply will always be the same. It's not like they somehow magically store up a few hundred amps. And with just two 160w panels, i just don't see it being an issue.

As for the switch, there is just not that much current in this setup. I have some similar cheap switches and regularly am switching close to 75 amps and never had a problem. I occasionally check for heat and voltage drops, but none so far.
 
It’s a 600amp one like this View attachment 63770

Such a switch (assuming it is a quality one) is meant for high current, low voltage.
It could be used between SCC and battery (or inverter and battery).
Did you use this between PV panels and SCC?

1) It might not successfully open the circuit, depending on Voc of PV string
2) Whether it opens or not, that shouldn't damage the SCC.

Are you sure this switch wasn't between SCC and battery? in that case, possibly opening during high-current charging would cause a high voltage spike.
 
Both amps and volts matter when choosing components.

You used a 12V switch on solar panels that easily provide much more than 12V (especially if the panels are in series).

You have a charge controller that supports up to 100Voc input and that input was controlled by a 12V switch.

You are lucky there wasn't far more serious results.

Please purchase components that are properly rated (volts and amps) for a given job. Please purchase high quality, well-known brand named components. Saving $10 or 10£ is a risk that could cost you a lot more.
 
1) It might not successfully open the circuit, depending on Voc of PV string

It's a mechanical rotary switch. Unlikely it would not open (short of a broken knob) under this or any voltage under 500 volts.
 
Both amps and volts matter when choosing components.

You used a 12V switch on solar panels that easily provide much more than 12V (especially if the panels are in series).

12v or 80v is not going to make any significant difference. Especially not at the voltage and current levels of 2 panels.
 
It's a mechanical rotary switch. Unlikely it would not open (short of a broken knob) under this or any voltage under 500 volts.

I wouldn't be surprised if this switch could hold off 500 VDC in the open position. Likely has sufficient creepage and clearance distances.

I also wouldn't be surprised if, when manually rotating a switch that doesn't have snap-action and interrupting some hundreds of volts and several amps from PV, that it would draw an arc, burn the plastic surface (tracking), and then continue to conduct indefinitely through the newly formed carbon resistor until the switch had completely burned apart.

One reason such a failure might not actually occur is that SCC with its input caps would typically be at Vmp, and open-circuit PV would rise to Voc. That's a relatively low voltage delta, so might not arc. Still could with a high-voltage series PV string like mine, where Vmp = 380V an Voc = 480V. I use a 600VDC rated switch.

If the rotary switch was closed into a short circuit and then opened, it would have full Voc across it. In that case at higher voltages well above rating I would expect it to burn. I was doing exactly that last weekend (to measure Isc, Voc, etc.) but with a suitably rated switch.
 
If the rotary switch was closed into a short circuit and then opened, it would have full Voc across it. In that case at higher voltages well above rating I would expect it to burn

The OPer has two 165w panels. Even in full sun, we are talking about 20 amps (if in parallel). I doubt the switch could not handle it.

Full Voc of two 165w panels in series is about 80v. I don't consider that to be above the rating of a 12v 600a switch, or even anywhere near it. Again, 12-80vdc makes little if any difference at these low current rates when the contacts are rated for 600a. Even if we derate them to 300a, it is still well above anything I would worry about in this setup. 80v is well below any serious arcing concerns.

The OPer can simply open up the switch (4 screws) and take a look for any damage. I doubt there is any.
 
The OPer has two 165w panels. Even in full sun, we are talking about 20 amps (if in parallel). I doubt the switch could not handle it.

Full Voc of two 165w panels in series is about 80v. I don't consider that to be above the rating of a 12v 600a switch, or even anywhere near it. Again, 12-80vdc makes little if any difference at these low current rates when the contacts are rated for 600a. Even if we derate them to 300a, it is still well above anything I would worry about in this setup. 80v is well below any serious arcing concerns.

The OPer can simply open up the switch (4 screws) and take a look for any damage. I doubt there is any.
The scc was saying it was only making 5 amps just before turned the switch.

I opened it up and all looks fine. 91B8036E-76AD-43B4-AFC6-6060931D3424.jpeg

its a mystery why turning the switch make the scc pop! It’s only a week old! Iv done the same thing many times on my old epever scc without any ill effects!

there is writing inside that says ‘ignition max 50v DC’ I don’t know if this is Relevant?
I don’t think the panels every make anywhere near 50v anyway.
 
I opened it up and all looks fine.

To really check it, you need to remove the cables and remove those four screws to look at the contacts. But I suspect they are fine.
If you do that, the back plate is under a little spring pressure but nothing will go flying.
 
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