The need for blocking diodes in a battery charging solar array?

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T1 Terry
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The need for blocking diodes in a battery charging solar array?

Post by T1 Terry » Mon, 28 May 2018, 10:32

After bring this topic up within another thread that I can't seem to remember where or who it was, I was informed that blocking diodes were a thing of yester-year and no longer required in a solar array.
After accepting this advice I have had to replace over $10,000 worth of solar panels and tried every other path to solve the issue until returning to the blocking diodes and the problem was finally solved.
So, now I'm interested in the theory behind the recommendation that blocking diodes were not required on a battery charging solar array where a number of panels or groups of panels were connected in parallel to single controller. Anyone want to put their views forward?

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Re: The need for blocking diodes in a battery charging solar array?

Post by weber » Mon, 28 May 2018, 18:51

T1 Terry wrote:
Mon, 28 May 2018, 10:32
After bring this topic up within another thread that I can't seem to remember where or who it was, I was informed that blocking diodes were a thing of yester-year and no longer required in a solar array.
Since the publication of AS/NZS 5033 in 2005, blocking diodes have not been required for the purpose of preventing current flow between parallel strings when some are shaded and some are in sun. But you must have string fuses when you have more than two strings in parallel.

A string is a number of panels connected in series. Of course, each string must consist of the same number of panels of the same type.

Neither have blocking diodes been required to prevent reverse current from a battery into an array at night, although some device should provide that function. Solar charge controllers normally provide that function using MOSFETs or relays.
After accepting this advice I have had to replace over $10,000 worth of solar panels and tried every other path to solve the issue until returning to the blocking diodes and the problem was finally solved.
I'm very interested to know how the panels were wired up, and in what way they failed? What make and model of panels, what string fuses and what solar charge controller? How many panels in each string? How many strings? What battery voltage?

There are thousands of solar power systems in Australia with parallel strings, charging batteries, with no blocking diodes.
So, now I'm interested in the theory behind the recommendation that blocking diodes were not required on a battery charging solar array where a number of panels or groups of panels were connected in parallel to single controller. Anyone want to put their views forward?
It's simple. The voltage of a solar panel increases with irradiance and decreases with temperature. A shaded panel has less irradiance but it is also at a lower temperature, the two effects tend to cancel out so a shaded string has about the same voltage as one in full sun and so there is very little reverse current. A blocking diode just wastes power and is another thing that can fail.

That old thread is here: viewtopic.php?t=4588
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Re: The need for blocking diodes in a battery charging solar array?

Post by jonescg » Mon, 28 May 2018, 19:13

Interesting - and I presume that if you do pop a fuse on a series string, you've probably set the arrays out wrong?

After all, replacing the fuse would simply let it happen again, and again, until you got up and pruned that tree?
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Re: The need for blocking diodes in a battery charging solar array?

Post by weber » Mon, 28 May 2018, 19:32

jonescg wrote:
Mon, 28 May 2018, 19:13
Interesting - and I presume that if you do pop a fuse on a series string, you've probably set the arrays out wrong?

After all, replacing the fuse would simply let it happen again, and again, until you got up and pruned that tree?
Good question, but no. A string fuse won't blow merely because of differential shading. The string fuses are there in case of a short-circuit fault in a panel (such as a shorted bypass diode) or in the wiring, whose effect is to make one string have fewer cells in series than the other strings.
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Re: The need for blocking diodes in a battery charging solar array?

Post by T1 Terry » Tue, 29 May 2018, 12:12

No idea what happened but the post went into the ether, I'll try again.
Thankyou for that link Weber, I hadn't even seen that thread, the one I was thinking of must have been the trigger for starting that thread.
I'm very interested to know how the panels were wired up, and in what way they failed? What make and model of panels, what string fuses and what solar charge controller? How many panels in each string? How many strings? What battery voltage?
The panels were semi flexible 100w nom. 12v panels all connected in parallel. The failure was one of the modules actually cracking through and breaking the series string within the panel. Each panel has 2 series strings in parallel so initially the panel output dropped to 50%, then a module in the other string would fail killing that panel. This process would continue until only one or two panels remained in the parallel circuit.

I tried a different medium to transfer the heat away, I tried not gluing either the panel to the medium or the medium to the RV roof and allowing the whole lot to move independently only secured by the 6 or 8 (depending on manufacturer) eyelets via 4mm screws and nuts anchored into a 3mm piece of aluminium glued to the roof.
In the end I added 10 amp rated Schottky diodes to the positive output from each panel and the problem hasn't occurred since.

I am theorising that when the battery reaches fully charged the solar array is disconnected via the solar controller allowing the array to climb to open circuit voltage. Because there is no such thing as a zero resistance cable or connection it allowed the solar array to generate current because none of the panels were pulled down to zero current. This high voltage at potentially the full current generation possible from the whole array was seen at every junction and every module in the array and any module that was not quite as good as the rest became the weak spot and this current was fed back into the module turning it into a heater till it expanded so much it cracked, either that or the constant expanding and contracting finally resulted in the module fracturing and breaking the circuit.
This destruction continued until the max current produced was not enough to break down any of the remaining modules and this explains why some panels always survived where the majority failed.
By adding the blocking diode the max current any module will experience is that of a single panel and therefore able to withstand the current backflow into any of the modules within that panel

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Re: The need for blocking diodes in a battery charging solar array?

Post by weber » Tue, 29 May 2018, 18:31

Are you saying the problem began with mechanical damage to one panel, which then caused a cascading failure of most of the other panels by overheating? Or could the first panel have failed in the same way as the others, and just happened to be the first one to go?

You don't mention anything about fuses. How many panels did you have in parallel? Clearly more than 2. Therefore you should have had a 10 amp fuse in series with each panel, in the locations where you now have the blocking diodes. In fact you should still have fuses in series with the blocking diodes. AS 5033 specifically says that blocking diodes are not a substitute for fuses.

Do these panels consist of 32 cells in a 4 x 8 arrangement, each cell being 125 x 125 mm? Like these?

If so, they can't possibly have two strings of cells in parallel within a panel. The voltage would be too low. All 32 cells must be in series, but I'd expect there to be a bypass diode across each group of 16. Are there bypass diodes in the panel junction boxes?

There seem to be lots of stories of failures of semi-flexible panels, on the web. Are yours a reputable brand? How long has it been since you've replaced them and added blocking diodes? How long did it take for the first failure to occur? Is everything else exactly as before, other than the diodes?
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Re: The need for blocking diodes in a battery charging solar array?

Post by T1 Terry » Wed, 30 May 2018, 11:10

The first knowledge of a problem was the RV owner calling to say the battery wasn't charging as well as it did before on solar only. I would say the panel failure was a cascading affair with the weakest failing first and the strongest being the only survivors. On 2 systems where the panels failed a second time, always less that 12 mths from install, the same 2 panels were the only survivors, on a few of the other one new panel and one of the previous survivors were the last ones still working.
Yes, there are bypass diodes in the terminal block and if a module in one side only fails the output drops to 2.5 amps short circuit tested but still shows 18v open circuit. It is possible the 2.5 amps is at a much lower Mpv, I haven't checked that. Sometimes a panel will work after a cold over night for a few hrs until the panel warms up, then it dies again, others are dead no matter what. The ones the work when cold appear to have the cracks close up and are very hard to detect until the panel warms up and at that point the panel stops working.

No parallel set exceeds 40 amps and is protected by a 40 amp DC circuit breaker. As the max voltage is 20v it falls well and truly into the ELV category and as it is not back to grid there are really no rules applicable. Every caravan and motorhome builder and reseller along with a few 100,000 auto electricians would be in the firing line if that was the case, then another few hundred thousand folk who deploy portable panels every time they camp out.

A fuse in a solar panel cable is complete waste of time and just adds another point for failure and adds resistance to the circuit. If the fuse is heavy enough not to fail under the max panel output then what would make it fail as a protection device? Far better to use a double pole DC circuit breaker close to the controller end of the circuit so all cable the other side of the circuit breaker was protected, not just the bit at the solar panel. As long as any cabling before the circuit breaker is rated for a continuous load greater than the trip value of the circuit breaker it has a short circuit current rating far exceeding the trip rating of the circuit breaker. I always install a fuse between the controller positive output and the battery as well, so one or the other will fail in the event of a short circuit.

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Re: The need for blocking diodes in a battery charging solar array?

Post by T1 Terry » Wed, 30 May 2018, 11:21

Missed a few bits, they are similar to the one in the JayCar link but they come in many variants, often from the same seller. As far as reputable brands, a bit of a joke because just about all nom. 12v and 24v solar panels under 200w are badge engineered so the same manufacturer can have any number of brand names on their panels. A lot of the stuff we use now we have a direct link to the factory so we can double check serial numbers to make sure the panels are not from a reject or seconds batch so we could eliminate that being the initial cause.

As far as failure rates since we started fitting the blocking diodes, none have been reported over the last 12 mths or more, I'd need to double check when we did the first diode install to see just how long the longest has been out on the road. Just about all our system installs are full time on the road so the RV is their house on wheels so the system is really a mobile off grid install so it must meet many more requirements than a house off grid system. Vibration is the biggest but trying to scrap the panels off under trees comes in a close second and Cockatoo attack probably equal second, so everything must be well attached and well protected and never be the cause of a water leak, those can be incredibly expensive to rectify any resultant damage.

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Re: The need for blocking diodes in a battery charging solar array?

Post by weber » Thu, 31 May 2018, 18:07

Hi Terry.

This looks like good advice re semi-flexible panels. Apparently there are some reputable brands. They use SunPower cells.
https://www.solar4rvs.com.au/buying/buy ... exible-so/
But the whole idea of using something as brittle as monocrystalline silicon in a flexible panel seems nuts to me.

You haven't said what make and model of solar charge controller (SCC) you're using, or whether it has some means of preventing backflow from the battery into the panels at night.

Have you checked the bypass diodes in any of the failed panels, with a meter, to see if they are still diodes?
T1 Terry wrote:
Wed, 30 May 2018, 11:10
No parallel set exceeds 40 amps and is protected by a 40 amp DC circuit breaker.
How many panels do you have in parallel on each 40 A breaker? How many 40 A breakers are there feeding one SCC? Are these breakers polarity sensitive?
As the max voltage is 20v it falls well and truly into the ELV category and as it is not back to grid there are really no rules applicable.
The laws of physics are still applicable -- in particular the laws of electrical circuits. And although AS/NZS 5033:2014 may not be a legal requirement for your systems, it still contains the best practice for designing and installing a PV array. Its scope includes all PV arrays except for "PV arrays in portable equipment of less than 240 W and less than 50 V open circuit." and "PV arrays of greater than 240 kW".
A fuse in a solar panel cable is complete waste of time and just adds another point for failure and adds resistance to the circuit.
Man, that is soooo wrong.
If the fuse is heavy enough not to fail under the max panel output then what would make it fail as a protection device?
Other strings that are in parallel with it, that's what. If one string has a short that bypasses some cells, such as a shorted bypass diode, or if shading somehow really is the cause of your failures, then that string will be at a lower voltage than all the other strings, and so they will force their current backwards through it. Isn't that why you've now installed blocking diodes? (And you still need the fuses because the diodes can fail short-circuit).

e.g. if you have 4 panels in parallel on the same 40 A breaker, then if one panel is at a lower voltage, the other 3 panels can force 15 amps or more through it in reverse, which will destroy it, and possibly set fire to nearby flammables.
Far better to use a double pole DC circuit breaker close to the controller end of the circuit so all cable the other side of the circuit breaker was protected, not just the bit at the solar panel.
This is needed too, but it doesn't replace the need for string fuses to protect the panels from each other.

I'm sorry for your loss. It seems a little soon to declare that the blocking diodes have solved the problem, however it is possible that you do need blocking diodes due to some unusual property of these panels. But if so, the panel manufacturer should have said so in the datasheet. Or perhaps it is due to shading in combination with your extreme degree of parallelism. You still haven't told us what that is.

But I really don't think I could have been any clearer, in that 2015 thread, than in this post, which ended with:
weber wrote:
Mon, 22 Jun 2015, 06:37
That's why, whenever we have more than two strings in parallel, the law requires us to put a fuse in every string ...
Had you installed such fuses, you may have had nuisance blowing of fuses, which would have alerted you to a problem, but you would not have had blown panels. Weatherproof MC4 inline fuses are readily available.
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Re: The need for blocking diodes in a battery charging solar array?

Post by T1 Terry » Fri, 01 Jun 2018, 12:57

weber wrote:
Thu, 31 May 2018, 18:07
Hi Terry.

This looks like good advice re semi-flexible panels. Apparently there are some reputable brands. They use SunPower cells.
https://www.solar4rvs.com.au/buying/buy ... exible-so/
But the whole idea of using something as brittle as monocrystalline silicon in a flexible panel seems nuts to me.
These panels are sourced from the same suppliers as we use. They have also gone to using blocking diodes.

You haven't said what make and model of solar charge controller (SCC) you're using, or whether it has some means of preventing backflow from the battery into the panels at night.
A single controller remote controlling multiple Solid State Relays (SSR) and each string had a blocking diode after the SSR to prevent backflow because each SSR has a diode as part of its internal protection circuitry
Have you checked the bypass diodes in any of the failed panels, with a meter, to see if they are still diodes?
They are still intact and functional
T1 Terry wrote:
Wed, 30 May 2018, 11:10
No parallel set exceeds 40 amps and is protected by a 40 amp DC circuit breaker.
How many panels do you have in parallel on each 40 A breaker? How many 40 A breakers are there feeding one SCC? Are these breakers polarity sensitive?
Every SSR has its own DC circuit breaker, blocking diode and fuse after the SSR to protect that circuit. The circuit breakers are double pole but not polarity sensitive.
As the max voltage is 20v it falls well and truly into the ELV category and as it is not back to grid there are really no rules applicable.
The laws of physics are still applicable -- in particular the laws of electrical circuits. And although AS/NZS 5033:2014 may not be a legal requirement for your systems, it still contains the best practice for designing and installing a PV array. Its scope includes all PV arrays except for "PV arrays in portable equipment of less than 240 W and less than 50 V open circuit." and "PV arrays of greater than 240 kW".
Hmmm.... best practice is a debatable topic I guess, adding resistance and failure points is not best practice in my book.
A fuse in a solar panel cable is complete waste of time and just adds another point for failure and adds resistance to the circuit.
Man, that is soooo wrong.
Ummm.... so are you saying a fuse and associated junctions has no resistance and at such a low voltage of no consequence?
If the fuse is heavy enough not to fail under the max panel output then what would make it fail as a protection device?
Other strings that are in parallel with it, that's what. If one string has a short that bypasses some cells, such as a shorted bypass diode, or if shading somehow really is the cause of your failures, then that string will be at a lower voltage than all the other strings, and so they will force their current backwards through it. Isn't that why you've now installed blocking diodes? (And you still need the fuses because the diodes can fail short-circuit).
ummm.. again, if the fuse is rated high enough not to fail during those freak solar events where a panel output could be doubled, how would that protect the panel? Remember the output from 2 panels in parallel was not enough to fracture a module yet 3 was enough so the fuse of sufficient capacity to fail regularly would not protect the current from 3 panels if the diode for some reason failed.
e.g. if you have 4 panels in parallel on the same 40 A breaker, then if one panel is at a lower voltage, the other 3 panels can force 15 amps or more through it in reverse, which will destroy it, and possibly set fire to nearby flammables.
A shaded panel does not have a lower voltage as such, just very little or no output so it is self blocking while exposed to even shade effected sunlight. There is no risk of a fire or flammable materials near by being ignited that isn't there due to the heat generated through a high resistance fuse or MC4 connector. I have a number of melted MC4 connectors here so I know they are a real problem so we no longer rely on the poor connection they provide but rather solde the pins together.
Far better to use a double pole DC circuit breaker close to the controller end of the circuit so all cable the other side of the circuit breaker was protected, not just the bit at the solar panel.
This is needed too, but it doesn't replace the need for string fuses to protect the panels from each other.

I'm sorry for your loss. It seems a little soon to declare that the blocking diodes have solved the problem, however it is possible that you do need blocking diodes due to some unusual property of these panels. But if so, the panel manufacturer should have said so in the datasheet. Or perhaps it is due to shading in combination with your extreme degree of parallelism. You still haven't told us what that is.

But I really don't think I could have been any clearer, in that 2015 thread, than in this post, which ended with:
weber wrote:
Mon, 22 Jun 2015, 06:37
That's why, whenever we have more than two strings in parallel, the law requires us to put a fuse in every string ...
Had you installed such fuses, you may have had nuisance blowing of fuses, which would have alerted you to a problem, but you would not have had blown panels. Weatherproof MC4 inline fuses are readily available.

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Last edited by weber on Sat, 02 Jun 2018, 08:32, edited 1 time in total.
Reason: Fixed incorrect quoting
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Re: The need for blocking diodes in a battery charging solar array?

Post by weber » Sat, 02 Jun 2018, 09:04

T1 Terry wrote:
Fri, 01 Jun 2018, 12:57
These panels are sourced from the same suppliers as we use. They have also gone to using blocking diodes.
Did they say why?
You haven't said what make and model of solar charge controller (SCC) you're using, or whether it has some means of preventing backflow from the battery into the panels at night.
A single controller remote controlling multiple Solid State Relays (SSR) and each string had a blocking diode after the SSR to prevent backflow because each SSR has a diode as part of its internal protection circuitry
What are you calling a "string" here? A string is a set of panels connected in series. I understood you did not have any series connections at all, so a string, for you, is a single panel.
How many panels do you have in parallel on each 40 A breaker? How many 40 A breakers are there feeding one SCC? Are these breakers polarity sensitive?
Every SSR has its own DC circuit breaker, blocking diode and fuse after the SSR to protect that circuit. The circuit breakers are double pole but not polarity sensitive.
OK. But you still haven't said how many panels are in parallel on each SSR and breaker, or how many SSRs and breakers you have?
A fuse in a solar panel cable is complete waste of time and just adds another point for failure and adds resistance to the circuit.
Man, that is soooo wrong.
Ummm.... so are you saying a fuse and associated junctions has no resistance and at such a low voltage of no consequence?
No. I'm saying that a fuse in a solar cable is soooo far from being a complete waste of time its not funny (when you have more than two in parallel). The resistance is negligible. Genuine MC4s do not fail. And the voltage drop across a fuse is less than that across a blocking diode.
If the fuse is heavy enough not to fail under the max panel output then what would make it fail as a protection device?
Other strings that are in parallel with it, that's what. If one string has a short that bypasses some cells, such as a shorted bypass diode, or if shading somehow really is the cause of your failures, then that string will be at a lower voltage than all the other strings, and so they will force their current backwards through it. Isn't that why you've now installed blocking diodes? (And you still need the fuses because the diodes can fail short-circuit).
ummm.. again, if the fuse is rated high enough not to fail during those freak solar events where a panel output could be doubled, how would that protect the panel? Remember the output from 2 panels in parallel was not enough to fracture a module yet 3 was enough so the fuse of sufficient capacity to fail regularly would not protect the current from 3 panels if the diode for some reason failed.
I posted earlier that it should be a 10 amp fuse in this case. This will not blow with normal operating current even under the most freaky sky conditions. But it will definitely blow with the current from 3 other panels feeding back through it, possible even the current from 2 other panels since short circuit current at STC is 6 amps for these panels.
e.g. if you have 4 panels in parallel on the same 40 A breaker, then if one panel is at a lower voltage, the other 3 panels can force 15 amps or more through it in reverse, which will destroy it, and possibly set fire to nearby flammables.
A shaded panel does not have a lower voltage as such, just very little or no output so it is self blocking while exposed to even shade effected sunlight.
That's what I've been saying since 2015. If you agree with that, then why do you think every panel needs a blocking diode?
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Re: The need for blocking diodes in a battery charging solar array?

Post by T1 Terry » Sat, 02 Jun 2018, 13:25

The problem is not shaded panels, the problem is a solar array with no where to feed its generated current so this generated current at what ever voltage it reaches short of absolute open circuit voltage finds weak spots within the panels in the array.
A fuse will not protect the panel from being exposed to this current/backflow where a Stocky diode rated at double the expected output will.
You are suggesting the fuse may have less resistance than the Stocky diode is that is the only connecting joint in the cable running from the cable from the panel to the controller and that may well be the case if the fuse was soldered into the cable run, but not if it is a plug in fuse. A plug in fuse has the connector to cable joint, fuse to connector joint, fuse to connector joint on the other end and the connector to cable joint, yet it still offers no protection to reverse current flow that is less than the rupturing capacity of the fuse. A 10 amp fuse is hardly enough for double the potential output from a 100w panel as you already mentioned the STC short circuit output is just under 6 amps, double that is 12 amps so a 15 amp fuse is required to protect against continuous issue with fuse failures, never a good look in a commercial installation. The problem is the output from 3 panels is apparently enough to cause a module failure yet the normal output from 3 panels is a little less than 15 amps, therefore a 15 amp fuse is of no value in protecting the panel from reverse current flow.
This means both the Stocky diode and the fuse with all of the inherent resistances is required even though the 15 amp fuse will offer no protection .......... back to my previous statement, the fuse is a complete waste of time.
The circuit breaker to panel ratio is designed to minimise the risk of false tripping, so the string or chain if you would prefer of paralleled panels must add up to less than a constant 40 amps and less than the combined cloud edge effect current over time that would normally trip the circuit breaker. They do have some short term over current capacity so generally 5 panels wit an STC max output of 5.5amps through a 40 amp circuit breaker allows for that cloud edge effect or cloud reflection that can increase a panels output not to trip the circuit breaker. The SSR is rated to 100 amps continuous with a short term 125 amp capacity and the fuse is a midifuse rated at 50 amps. We were forced to move to midi fuses and holders after a number of mini ANL fuses and holders melted, so there is more than one example of the fuse in circuit resistance/heat generation that we use as a base for our choice not to use fuses in each solar panel.
The number of circuit breakers, SSR and midi fuses depends on the number of panels, 20 is our biggest system so far so that required 4 sets but still only the one controller. A system with less than 7 panels would only have one SSR and fuse, 7 panels would have the 3 panels furthest from the junction box on one circuit and the 4 panels closest on the other circuit.
As far as the string being panels in series? Maybe your definition but a string of lights in parallel is still a string so .......

Why did Solar4RV go to installing/insisting on blocking diodes be used or a warranty claim would not be honoured? They had the same problem as we did but they went about it by making a multiple MC4 link with diodes in each and charging a price I'm guessing factor in a recovery percentage for the losses in the past. A member on another forum who purchased the Solar4RV panels has had 3 sets or maybe 4 sets replaced under warranty and the diodes were part of the requirement for further warranty claims. So far he has had 2 yrs without a failure so the blocking diodes appear to have worked in his case as well. I only discovered this after mentioning about blocking diodes on a thread there.

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Re: The need for blocking diodes in a battery charging solar array?

Post by weber » Sat, 02 Jun 2018, 21:10

I'm sorry Terry, but your description of the behaviour of currents and voltages seems to bear little resemblance to reality. And it took me a while to realise you were talking about schottky diodes. :)

We're talking about solar panels, not lamps. The definition of a PV string is not mine. It is standard terminology all over the world, including in AS 5033.

I don't understand why you think you know better than AS 5033, which is a distillation of decades of experience by solar power system researchers, designers and installers. It tells us we can use a string fuse with a rating as low as 1.5 times the short circuit current. It has been used to install thousands of systems in Australia without any nuisance blowing due to cloud halo effects.

Have you heard of time-current curves for fuses? A typical 10 amp fuse will carry 12 amps for about two hours. Cloud halo effects that cause double the normal operating current don't last for 2 hours. But at 15 amps, a 10 amp fuse will only last for about a minute and a half.
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Re: The need for blocking diodes in a battery charging solar array?

Post by T1 Terry » Thu, 07 Jun 2018, 17:12

Sorry Weber, been away for a while doing jobs, got the spell checker to blame for the spelling change and me to blame for not realising it had changed it on the fly, so now I have added it to the dictionary so hopefully it won't happen again.
That bit about nuisance fuse blowing not happening on systems installed in Australia could be a little stretch of the truth, the system I've just installed also has a back to grid system installed and nuisance fuse failures was the reason I got the job to do the off grid install in the first place rather than the local bloke. Since I installed this off grid system he has had a further 3 fuse failures and an inverter failure on his grid connect system and he told them in desperation to forget about it and he'd get me to add more batteries and link that solar array up as well. Suddenly the inverter was replaced at no charge and a system that puts out a warning both back to base and to the owner that the fuse has failed or the system has stopped putting out power.
AS 5033 more relates to Grid connect and much higher voltage series solar strings than used for 12v battery charging using a PWM controller so using that standard as a reference to battery charging off grid 12v systems is about as relevant as using stats from a grid connect system to support the benefits of MPPT over PWM for 12v battery charging ... but no doubt that has just opened yet another Pandora's Box :lol: I guess if you don't work in the 30vdc or lower field the problems would not show up so there would be no reason to investigate the cause.

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weber
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Re: The need for blocking diodes in a battery charging solar array?

Post by weber » Thu, 07 Jun 2018, 20:37

T1 Terry wrote:
Thu, 07 Jun 2018, 17:12
That bit about nuisance fuse blowing not happening on systems installed in Australia could be a little stretch of the truth, the system I've just installed also has a back to grid system installed and nuisance fuse failures was the reason I got the job to do the off grid install in the first place rather than the local bloke.
Of course I never claimed that nuisance fuse blowing never occurs on systems installed in Australia. I'm only claiming that it occurs extremely rarely on systems designed to AS/NZS 5033:2014.

How do you know the local bloke actually sized his fuses according to AS/NZS 5033:2014? What make and model of panels were they? What fuse rating was used?
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

T1 Terry
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Real Name: Terry Covill
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Re: The need for blocking diodes in a battery charging solar array?

Post by T1 Terry » Sun, 10 Jun 2018, 13:46

weber wrote:
Thu, 07 Jun 2018, 20:37
T1 Terry wrote:
Thu, 07 Jun 2018, 17:12
That bit about nuisance fuse blowing not happening on systems installed in Australia could be a little stretch of the truth, the system I've just installed also has a back to grid system installed and nuisance fuse failures was the reason I got the job to do the off grid install in the first place rather than the local bloke.
Of course I never claimed that nuisance fuse blowing never occurs on systems installed in Australia. I'm only claiming that it occurs extremely rarely on systems designed to AS/NZS 5033:2014.

How do you know the local bloke actually sized his fuses according to AS/NZS 5033:2014? What make and model of panels were they? What fuse rating was used?
Not my system so I didn't bother looking, that is a quick way to get the blame the next time a fuse blows. All solar/electrical installs are inspected by the local authority in that area because they are very "Old Skool" where solar is believed to be smoke and mirrors and batteries could never replace coal fired mains power so they nit pick anything and everything.

T1 Terry
Green but want to learn

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