Switch to turn off power from solar panels

[Whereverimayroambus]

I recently got 4 Renogy 300W solar panels. I plan on installing them on my skoolie roof soon.
I want to be able to cut the power coming from the panels before it gets to my solar charge controller so if I need to work on something in the system I can do so safely.
How? or what can I use to safely accomplish this?
Is it ok if the panels are disconnected for a long period of time, aka if the vehicle was in storage/ not in use?

 

[Craig]

Yes its ok to leave then turned off for extended periods. I use a dual pole circuit breaker to turn my panels off.



something like this. Obviously get one that meets your panels output specs

 

[Thor]

This is what I use between my panels and the mppt.

https://www.amazon.com/gp/product/B07413JWLD/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

 

[gnubie]

The important things to look for in a PV isolator are

• can it carry the array's short circuit current
• can it handle the array's open circuit voltage
• always use a switch that exceeds these values by at least 10%
• the switch must be rated to break DC at these values

A breaker will usually have an arc trap in it so that if an arc is drawn when the contacts are open it will be safely extinguished. A run of the mill DC switch usually won't.

 

[brassmonkey001]

I've got one of these: https://www.amazon.co.uk/gp/product/B07J67X3NQ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
I've got to be honest, I'm not sure if it's up to the job so would appreciate some feedback.
I have two 265W panels wired in series and this is the spec. of the panels:

 

[gnubie]

It's not. The VoC of the panel is 38.12v. The switch is not rated to break that voltage. Add in a 2nd panel and there's a good chance an arc will form and persist and melt things if not cause things to catch on fire.

 

[Thor]

gnubie - This is good information, thanks. Can you recommend a switch that handles a voc in the 60-100 volt range.
The one I posted above has been working fine for me, but now you have me worried.

 

[gnubie]

Craig posted a picture of the sort of thing that would do the job. This is the sort of thing from ebay. I can't say if that one is a quality device, it could be a knock off, but it'll give you a point to start searching from. Don't forget the amp rating, ensure it is at least the current your array can provide shorted, but a bit above that is recommended.

If you find a breaker you like but aren't sure, post a link here and someone will take a look for you.

 

[brassmonkey001]

It's not. The VoC of the panel is 38.12v. The switch is not rated to break that voltage. Add in a 2nd panel and there's a good chance an arc will form and persist and melt things if not cause things to catch on fire.

Thanks gnubie, I'd best get that changed sharpish then!
So in order to work out what I need, in my example, my Short Circuit Current (Isc) per panel is 9.01A, but as I have two panels in series I have to double that to 18.02A, so I need a breaker that breaks at a figure lower than that e. g. the 16A you linked to. Is that correct?
If I only had one panel, or two in parallel, would that mean I'd need an 8A breaker?
And for Open Circuit Voltage (VoC) of 38.12v x 2 = 76.24v so I need something capable of handling more than 76.24v + 10% = 83.864v?

 

[gnubie]

The current through 2 panels (with identical specs) in series remains the same as 1 but you double the voltages. Panels in parallel are the other way around, you double the current but the voltage remains the same as one panel.

Since you have two panels in series your current is 9.01A and open circuit voltage is 76.24v. You'd be after a breaker that can handle at least 10 amps and at least 80v. If its a genuine item this one on ebay would cover you. It looks like its a DIN rail mount so that may not be convenient for you. I have the 32A version of it for my own system and so far it has worked nicely.

 

[brassmonkey001]

The current through 2 panels (with identical specs) in series remains the same as 1 but you double the voltages. Panels in parallel are the other way around, you double the current but the voltage remains the same as one panel.

Since you have two panels in series your current is 9.01A and open circuit voltage is 76.24v. You'd be after a breaker that can handle at least 10 amps and at least 80v. If its a genuine item this one on ebay would cover you. It looks like its a DIN rail mount so that may not be convenient for you. I have the 32A version of it for my own system and so far it has worked nicely.

Thank you, I understand now.
If I get a breaker rated for 20A and 100v then that would cover me if in the future I decided to change from series to parallel panels as well? Would that cause any issues with my current set up?

 

[gnubie]

Yes, that would handle it if you changed those 2 panels from series to parallel. Don't forget that the breaker needs to be DC rated.

 

[brassmonkey001]

Nice one gnubie, thank you.
Sorry to the OP for hijacking your thread!

 

[brassmonkey001]

This one?

20A DC Circuit Breaker MCB Solar Fuse 125v Single Pole 1P Ebike TOB1Z-63 C20 : Amazon.co.uk: DIY & Tools

20A DC Circuit Breaker MCB Solar Fuse 125v Single Pole 1P Ebike TOB1Z-63 C20 : Amazon.co.uk: DIY & Tools

www.amazon.co.uk

 

[ScoTTyBEEE]

This one?

20A DC Circuit Breaker MCB Solar Fuse 125v Single Pole 1P Ebike TOB1Z-63 C20 : Amazon.co.uk: DIY & Tools

20A DC Circuit Breaker MCB Solar Fuse 125v Single Pole 1P Ebike TOB1Z-63 C20 : Amazon.co.uk: DIY & Tools

www.amazon.co.uk

Yeah, there's lots on ebay too. If you look to the right of the bit where it says DC250v theres a line with dashes underneath, that means DC. If it's a ~ that means AC, some of them on ebay don't say DC/AC but use those lines.

Search for this: C65H-DC

 

[eddie1261]

<snipped for brevity>
Is it ok if the panels are disconnected for a long period of time, aka if the vehicle was in storage/ not in use?

I have to ask why you want to risk your batteries going dead during that long period of down time, possibly rendering them un-chargeable when you are ready to roll again. If your vehicle is going to be parked that long, take your batteries out and put them on a trickle charger. If they get past a certain point, someone please tell us that point, they go dead forever and you will be buying new.

To the "disconnected" part of the question, the same thought process applies. When your vehicle is in storage, and I assume by use of that word that it is in a garage or barn, there is no sun anyway.

Disconnect is a good idea for when you work on the system. That has been covered. Just switch the positive between the panel and the charge controller.

 

[brassmonkey001]

Yeah, there's lots on ebay too. If you look to the right of the bit where it says DC250v theres a line with dashes underneath, that means DC. If it's a ~ that means AC, some of them on ebay don't say DC/AC but use those lines.

Search for this: C65H-DC

I haven't come across a 20Amp breaker in that flavour, would this 32Amp one be right for my needs: https://www.amazon.co.uk/2-Pole-Cir...6:419158031&rnid=419157031&rps=1&s=diy&sr=1-2

 

[gnubie]

It sure would, 32A, 250VDC, covers both of your requirements. It is DIN rail mount but if you don't have that already you can get short rails off ebay for a few dollars, probably amazon too.

 

[brassmonkey001]

It sure would, 32A, 250VDC, covers both of your requirements. It is DIN rail mount but if you don't have that already you can get short rails off ebay for a few dollars, probably amazon too.

Thanks again gnubie, I'll get it ordered.
I've already got about 4" of DIN rail in my van, where the breaker between the MPPT and the battery sits. I can mount it on there I suppose although I would prefer them to be separate to avoid getting mixed up. I can probably scrounge another bit from somewhere, there might be some at work.