Fuse between solar panels and MPPT controller?

lustyd said:
My suggestion of a small guage wire test was to encourage you to understand the problem, I certainly never suggested you should use underrated wire other than to demostrate the idea that no damage would occur when loaded beyond it's rating. I've also never disputed that a properly designed system without modification would cause an issue, that has been consistently read into my words by others. While voltage drop can be important, cable rating must also be considered to ensure its current carrying capacity, and I find it odd that so many people are arguing against that.
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I do understand the potential problems but what you are raising is not a problem in the real world.
 
lustyd said:
Oh well, I tried. I've no desire to continue being insulted and you're clearly unwilling to consider anything outside of your world view so I'll leave you and block you there.
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Paul and I have had disagreements in the past but we do agree on this both Paul and I have been involved in Electrical installations myself also as a Design Engineer in industrial control and power systems.

We do consider you view but find no merit in your view so if you cannot or unwilling to see my/our input I will just leave it there and say we agree to differ.
 
Rogershaw said:
I do understand the potential problems but what you are raising is not a problem in the real world.
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In what way would it not be a problem? If the problem exists, and it's easy/cheap to mitigate against, then surely better to do so? All safety measures are there to protect against unexpected or unusual situations, so the fact that it's unlikely is not reason enough to avoid it.
 
Rogershaw said:
We do consider you view but find no merit in your view so if you cannot or unwilling to see my/our input I will just leave it there and say we agree to differ.
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I've been repeatedly insulted on this thead and told that it was completely impossible for any damage to occur. With respect that's horsecrap and you know it is. Whether you find merit in it or not, making things up to defend your world view and then insulting people because they challenge it is a poor show. If you'd simply agreed that upgrading a system will put extra load on the cables but that you disagreed there would be a scenario where the upgrade could be significant enough to cause danger that would have been a reasonable response. Arguing that solar panels cannot under any circumstances provide the current to overload a circuit completely undermined all credibility in those posting it for me, hence I didn't respect those responses. Why would I?
 
lustyd said:
Go on, tell us more...
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Why are you scouring my posts, going back to 2019 to find the first quote ?

You went all the way back to here: Battery main fuse

Just to try and find something to prove me wrong and yourself right LOL

You just can't grasp that there are different reasons for fitting fuses, or not.

If you are fusing a load carrying cable, it's to protect the cable and in some cases the equipment.

When fusing between a solar array and the controller, it's to protect against a shorted panel that could act as a load and overheat. Fitting a fuse how you said you would do it does nothing to provide that protection.
 
Note in this image that the solar array is being completely short circuited by the multimeter with it's skinny little cables:

Lensun-Portable-100w-DC-amps-testing-via-multimeter-logo.jpg


Edit: i inadvertently posted the image of the voltage test, now corrected by posting the current test.
 
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lustyd said:
I've been repeatedly insulted on this thead and told that it was completely impossible for any damage to occur. With respect that's horsecrap and you know it is. Whether you find merit in it or not, making things up to defend your world view and then insulting people because they challenge it is a poor show. If you'd simply agreed that upgrading a system will put extra load on the cables but that you disagreed there would be a scenario where the upgrade could be significant enough to cause danger that would have been a reasonable response. Arguing that solar panels cannot under any circumstances provide the current to overload a circuit completely undermined all credibility in those posting it for me, hence I didn't respect those responses. Why would I?
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This is a nice document giving all the technicalies of solar panels and page 17/18 talks about short circuit current equasions.

http://astro1.panet.utoledo.edu/~re...0131_PHYS_6980_4400_FundamentalProperties.pdf

A typical I/V curve for a solar panel

1615396999197.png
 
Rogershaw said:
Is the meter on voltage of current. If its current there would be a short but I don't think a volt meter would .
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That picture was taking reading volts, the following test was reading amps, short circuit.

How to Use Multimeter to Measure Volts and Amps of Solar Panel – Lensun Solar Panel – Lensunsolar

There'll be a million images on the internet showing the same thing and another million showing installation schematics of panels with no fuses, as we both know.
 
Rogershaw said:
Is the meter on voltage of current. If its current there would be a short but I don't think a volt meter would .
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If you enlarge the image you can clearly see that the meter is on DC voltage .
Definitely not short circuiting the panel.
Measuring its open circuit voltage!
 
VicS said:
If you enlarge the image you can clearly see that the meter is on voltage .
Definitely not short circuiting the panel.
Measuring its open circuit voltage!
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If you look at the link i posted you will see they tested voltage and current. Same panel, same meter, same cables.

To avoid any pedantry i've ammended the post with the other image.
 
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VicS said:
If you enlarge the image you can clearly see that the meter is on DC voltage .
Definitely not short circuiting the panel.
Measuring its open circuit voltage!
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I can’t tell if there’s a separate conversation here about short circuits or not. If so I apologise but that’s completely different to what I’ve been talking about.
 
I've a further question but afraid to ask (not!) - seems I started a bit of a bun fight here!

What I do take from posting on these forums is to be careful who's answers you trust, and to cross reference with other sources..... you'll learn something from the the good, bad and ugly responses.

Q: Do the panels need to be grounded?
Q: Should the +/- cables from the controller (via a breaker) go direct to the battery terminals? Or can they go to the central negative bus and the positive pre-main (ANL) fuse going to the house batteries? (as shown in this diagram from Victron)
https://www.victronenergy.com/uploa...charger-12-50-1-inverter-375W-MPPT-100-30.pdf
 
Victron also have a free online course if you want to get it straight from the horses mouth. You even get a certificate at the end :)
 
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