How about a solar car port on a budget?

[tjo o tjim]

7 hours ago, carlyai said:

Sorry if this is unhelpful, but there's a YouTube video by Sam Ben-Yaakov on building a MOSFET snubber. Bit more involved than a single capacitor.

Two different options— a snubber or a surge suppression capacitor with the MOV. The snubber is generally better, but the capacitor could do the job potentially.  
 

I would be curious if the enphase inverters have similar issues. At 4-5,000B for a single panel Microinverter the economics might not work though. 

[Crossy]

11 hours ago, Muhendis said:

That is undoubtedly a design shortfall.

 

No doubt whatsoever.

 

I still suspect the actual damage is occuring when the power goes off rather than when it returns (which is when the fuse pops).

 

The issue has certainly been around for a while if you look back at the various info on t'internet. I was rather hoping they'd sussed it with the updated design. There is no doubt that they are aware of the weakness, the support engineer immediately knew what was wrong and the spares needed to fix it when I described what had happened.

 

I agree there's not a lot we, as users, can do apart from keep fixing the fried FETs and hope that daytime power failures continue to be rare????

 

[Muhendis]

1 hour ago, Crossy said:

the actual damage is occuring when the power goes off rather than when it returns

The way to confirm this would be to disconnect city power next time you are on full load, then check the outputs of the individual micro inverters. Switching things back on again after this might be ok if the load is removed first.

Perhaps the supplier should include an inexhaustible supply of bits, a soldering iron and some explicit instructions. It seems that this micro inverter is not suitable for an unskilled novice.  

[sometimewoodworker]

1 hour ago, Crossy said:

 

No doubt whatsoever.

 

I still suspect the actual damage is occuring when the power goes off rather than when it returns (which is when the fuse pops).

 

I agree there's not a lot we, as users, can do apart from keep fixing the fried FETs and hope that daytime power failures continue to be rare????

 

I have no understanding of the way the Electronic systems work but logically wouldn’t it be possible to add in a normally off contactor into the mains connection so that the restore of the mains link is no longer automatic or can not happen while the panels are producing full power to the inverter when the mains link is re-established 

 

If the failure is not instantaneous with the power cut then a mains powered N.O. Contactor between the panels and the inverter might be able to cut the supply to the inverter before the majic smoke can escape.

 

please shoot down these ideas if they won’t work or you’ve already discarded them. 

[Crossy]

12 hours ago, tjo o tjim said:

I would be curious if the enphase inverters have similar issues. At 4-5,000B for a single panel Microinverter the economics might not work though. 

 

My investigations have concentrated on the WVC inverters although other micro inverters have popped up in the results with similar faults (fried MOSFETs).

 

I've also looked for more robust devices (the existing ones are 650V) but anything higher (1000V) at similar current rating (30A) are either not available in the TO-220 package and/or are considerably more expensive. 

[Crossy]

3 minutes ago, sometimewoodworker said:

If the failure is not instantaneous with the power cut

 

From other reports it seems that the failure IS instantaneous (very fast) when the power cuts. The shorted devices then sit there until the power returns at which point the fuse pops.

[sometimewoodworker]

7 minutes ago, Crossy said:

 

From other reports it seems that the failure IS instantaneous (very fast) when the power cuts. The shorted devices then sit there until the power returns at which point the fuse pops.

So not ideal and maybe not cost effective but the fuse popping part could probably be stopped with my idea?

[tjo o tjim]

10 minutes ago, sometimewoodworker said:

I have no understanding of the way the Electronic systems work but logically wouldn’t it be possible to add in a normally off contactor into the mains connection so that the restore of the mains link is no longer automatic or can not happen while the panels are producing full power to the inverter when the mains link is re-established 

A contractor operates in about 20ms, a fuse in about 5ms, and a MOV in about 3ms. The igbt switches in about 50us, which is the time required to protect. 
 

The problem is instantaneously you can get “infinite” reverse bias voltage across the SCR/IGBT, and the only real solution is to dissipate that energy. That happens when power returns generally. 

[Crossy]

By the way, the manufacturer will fix any failed inverters for free. You pay shipping both ways which equates to about half the cost of a replacement unit. I only got spares (again free + shipping) because the support staff understood that I'm in the position to actually fix the unit.

 

I've located a supplier of the devices on AliExpress for about 2 bucks a piece (with free shipping) which actually works out about the same as getting them from the manufacturer (6 FETs plus 2 fuses free + $15 express shipping) but they take 30 days to arrive.

 

I don't have the drawings but it seems these inverters may have one output stage per panel, it was only one pair of MOSFETs that actually failed (I'm replacing all 4 anyway, I'll keep the "good" ones for emergencies). There's a possibility that simply removing the failed devices and replacing the fuse would return the unit to operation at 50% output. I may try this next time, I have no doubt there will be a next time I'm afraid (I've ordered 20 spares which probably guarantees that I won't see another failure).

 

 

Slightly off-topic, but a lot of commercial electronics has a set of "stock" failures that appear after a design has been in service for a while. i.e. When you see one on your bench you can pretty much guarantee what the fix is. CPC (now long defunct) used to do repair kits for the popular chassis containing all the bits needed to fix the main faults. Most of the time the service chaps didn't even bother to diagnose the issue, just install the repair kit and test.

 

[RideJocky]

I may try this next time, I have no doubt there will be a next time I'm afraid (I've ordered 20 spares which probably guarantees that I won't see another failure).
 

Until you lose track of them...

[RideJocky]

If you had enough of them you could send them back four at at time making shipping more cost effective.

Particularly since you have plans to expand. At some point they’d get them right.

Of course that would take the fun out of it...


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[carlyai]

By the way, the manufacturer will fix any failed inverters for free. You pay shipping both ways which equates to about half the cost of a replacement unit. I only got spares (again free + shipping) because the support staff understood that I'm in the position to actually fix the unit.
 
I've located a supplier of the devices on AliExpress for about 2 bucks a piece (with free shipping) which actually works out about the same as getting them from the manufacturer (6 FETs plus 2 fuses free + $15 express shipping) but they take 30 days to arrive.
 
I don't have the drawings but it seems these inverters may have one output stage per panel, it was only one pair of MOSFETs that actually failed (I'm replacing all 4 anyway, I'll keep the "good" ones for emergencies). There's a possibility that simply removing the failed devices and replacing the fuse would return the unit to operation at 50% output. I may try this next time, I have no doubt there will be a next time I'm afraid (I've ordered 20 spares which probably guarantees that I won't see another failure).
 
 
Slightly off-topic, but a lot of commercial electronics has a set of "stock" failures that appear after a design has been in service for a while. i.e. When you see one on your bench you can pretty much guarantee what the fix is. CPC (now long defunct) used to do repair kits for the popular chassis containing all the bits needed to fix the main faults. Most of the time the service chaps didn't even bother to diagnose the issue, just install the repair kit and test.
 

Like a microwave system I consulted on, had a breadboard arrangement outside the main unit which containing connectors and all the transistors that blow up with lightning strikes. Just pop in a new set if T'sistors.

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[RideJocky]

What about a battery that can absorb the shock and allow a timed shutdown?


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[Crossy]

The most annoying part of this whole game is that the last 3 days since the inverter failed have been the best for generation on the remaining unit ????

 

Meanwhile the 1,200W unit should arrive Tuesday so next weekend will be extra panel installing time.

 

I'm also going to re-configure the DC wiring to minimise the cable lengths, got to get every last Watt ????

[BritManToo]

17 minutes ago, Crossy said:

The most annoying part of this whole game is that the last 3 days since the inverter failed have been the best for generation on the remaining unit ????

Meanwhile the 1,200W unit should arrive Tuesday so next weekend will be extra panel installing time.

I'm also going to re-configure the DC wiring to minimise the cable lengths, got to get every last Watt ????

My Suoer D600D GTI is still working and only costs 2,650bht from Lazada.

27.3 units from my one panel so far this month, lost 1 day to rain, and another 1/2 day to clouds.

The panel was getting a bit dusty so I gave it a wipe today, one day I'll get around to adding a second panel.

 

Just got my bill, 271 units 1,075bht.

[Crossy]

4 minutes ago, BritManToo said:

My Suoer D600D GTI is still working and only costs 2,650bht from Lazada.

27.3 units from my one panel so far this month, lost 1 day to rain, and another 1/2 day to clouds.

 

Are you going to give it another panel to play with and make it do some work near its ratings?

 

At that price it's certainly worth a look, my main concern would be that it's not sealed so the local wildlife could get in. We could be swapping one failure mode for another. I don't need waterproof but the units are in an "outside" location.

 

[BritManToo]

7 minutes ago, Crossy said:

 

Are you going to give it another panel to play with and make it do some work near its ratings?

 

At that price it's certainly worth a look, my main concern would be that it's not sealed so the local wildlife could get in. We could be swapping one failure mode for another. I don't need waterproof but the units are in an "outside" location.

 

My 330w panel only produces 200w, so I could add another 2 as it allegedly has over voltage and overcurrent protection.

I'd need to buy some more box steel and weld a new frame to mount any extra panels.

[Crossy]

https://www.lazada.co.th/products/tj-solar-solar-panel-poly-crystalline-300w-36v-sp300w-poly-i345194687-s673428785.html

 

3,550 Baht from Lazada but out of stock (as are the 300W mono panels) ????

 

Global House have the Trina 300W poly panels at 3,990 Baht, plenty of stock.

[BritManToo]

9 minutes ago, Crossy said:

https://www.lazada.co.th/products/tj-solar-solar-panel-poly-crystalline-300w-36v-sp300w-poly-i345194687-s673428785.html

 

3,550 from Lazada (but out of stock)

https://shopee.co.th/product/53019024/2055214342 ...... 3,650 with free shipping.

I'm not sure I could link different panels in parallel, so I'd stick to what I already have.

[Crossy]

2 minutes ago, BritManToo said:

https://shopee.co.th/product/53019024/2055214342 ...... 3,650 with free shipping.

 

I've not used Shopee, do they take plastic? Safe?

 

[BritManToo]

1 minute ago, Crossy said:

I've not used Shopee, do they take plastic? Safe?

You pay money direct to Shopee's bank account, I just use my Bangkok bank phone app to transfer, and they release the money to the supplier when you confirm delivery. I've had a couple of mobile phones and a solar panel through them, no problems so far.

[leogerritsen]

On 10/27/2019 at 11:14 AM, BritManToo said:

My Suoer D600D GTI is still working and only costs 2,650bht from Lazada.

27.3 units from my one panel so far this month, lost 1 day to rain, and another 1/2 day to clouds.

The panel was getting a bit dusty so I gave it a wipe today, one day I'll get around to adding a second panel.

 

Just got my bill, 271 units 1,075bht.

Do you have power cuts, while using the solar system to full capacity ?

[BritManToo]

8 hours ago, leogerritsen said:

Do you have power cuts, while using the solar system to full capacity ?

I have a 600w GTI and a 330W panel (which only produces 200w).

I'd need 2 more panels to see what happens at full capacity.

[Crossy]

OK, I've fixed the dead inverter (4 MOSFETs and a SMT 6.3A fuse). It didn't go bang when I connected it and it is communicating, just waiting for the sun to wake up and see how well it works. Two of the FETs I removed test as good, so they are in the "emergency spares" box in case we get another death without having new devices in stock (waiting for these from AliExpress).

 

I also stripped off the waterproof gasket on the rear cover and replaced it with 0.5mm silicone heat transfer pad (heatsink ointment is better but messy) in the hope that it will improve the passive cooling by better using the outside metalwork.

 

Testing continues.

 

Meanwhile a mate sent me this, no info other than it's at Amorn Solar, 3 fl. The Old Siam Tower (Ban Moh), large pile in stock. I can confirm it's 72 cell, 37V, 315 Watt, no info on branding I'm afraid. The Thai simply says "solar panel".

 

 

EDIT It lives!

Both 600W inverters are staggering to about 100W due to the total overcast and peeing rain. Ruddy typical.

EDIT 2 After an miserable damp day we've made a whole one unit ????

At least the repaired inverter hasn't died.

 

[Crossy]

So, we were up bright and early this morning installing another 4 panels, not from Amorn (I had already ordered the panels when I was told about those, maybe next time) but from a major online reseller.

 

I also added a 1,200W WVC inverter to see how it performs against the 600W units as it's rather cheaper per-watt.

 

 

That tree is going to get a haircut later today.

 

I've rationalised the DC cable lengths to save every available Watt,  so two inverters are at one end of the car port.

 

 

And one at the other.

 

 

And it's making power.

 

 

[Muhendis]

Back to the hot electronics and the trend to run hot. This trend is, I think, only at the budget end of the industry. Here are some pictures of a charge controller similar to the ones I am using. Note the size of the cooling fins and the inductors mounted in heat sink jackets. This unit is barely warm when charging at around 30 Amps into a 48v battery. The cost of this charge controller is 6,800 Baht plus postage from China. It has a multiplicity of settings for various battery types and voltages and there is loads of information at the 485 output port. Battery temperature compensation and four wire connection are standard. 

[Crossy]

Well, it's about a week since we added the additional panels and inverter. Over 7 days our 8 panels have averaged 7.95 units generated per day.

 

We currently have:-
WVC 1200 inverter with 4 panels (external fans)
WVC 600 inverter with 2 panels (external fans)
WVC 600 inverter with 2 panels (no fans)

 

I started off with the WVC 1200 with no fans but it rapidly became apparent that it was shutting down on overheat rather more often than I would like so fans were added. The fans haven't made as large a difference to the temperature as they did with the WVC 600s.

 

The WVC 1200 starts making power before either of the WVC 600 units and makes power slightly longer.

 

The WVC 1200 seems somewhat less efficient, it's currently making 688W whilst the WVC 600s are making 372W and 366W (total 738W).

 

I'm not going to buy another WVC 1200, rather I'll get more WVC 600 units. I did look at the baby WVC 300 units (1 panel), but they are only slightly cheaper than the WVC 600 which would run much cooler with only one panel connected if you wanted such a configuration.

 

I am going to persevere with the WVC 600 units now I have a reasonable cost way of keeping the temperatures within bounds. I like the sealed unit construction, I worry that the local wildlife would enter an inverter with forced ventilation, we could be swapping one failure mode for another.

 

There's still the problem of the units frying MOSFETs if the supply is removed whilst they are making power. We shall see just how often this is an issue, I have spare FETs and the fix only takes 30 mins or so (our inverters are easily accessible). Whilst the manufacturer has been most helpful in providing spares and assistance in fixing the beast that failed, they have been silent as to any means by which this failure mode can be mitigated.
 

 

[Crossy]

A quick update and bump.

 

In order to run the fans only during the day I got a bunch of these 

https://www.aliexpress.com/item/4000084041472.html 

 

At a whole $0.42 US (plus I paid the extra for tracked shipping) it's hardly worth building something.

 

Max input voltage 40V (the LM2596S is actually good to 45V), set for 12V output. Take the input from one of the panels (1 unit per inverter). Small plastic box 20 Baht from NPE.

 

Fans start when it's barely light.

 

 

[Muhendis]

You may need to place those step down modules (buck regulators) in front of the fan. They get hot also. If they didn't they wouldn't be cheap.

[Muhendis]

Looking at your picture again, are those soot stains I see? What happened?