What inverter?

So 2 years ago I bought a "new old stock" cheap make inverter for my solar PV and (as some of you predicted) it has now died.  It is outside it's manufacturers warranty and with no service information available unlikely to be repairable.

So i am looking for a replacement, 4kW dual MPPT and strictly speaking limited to 16A output

There are a bewildering number of makes most I have not heard of, and many that seem to have common faults.

Sunny Boy seems to be regarded as the best but I can't afford new price.  I have the chance of a second Hand SB3600-TL-20 for £250 in working order removed from a system upgraded to a battery storage system.  Is that a good price for a uses SB that could be per haps 10 years old?  could I expect that to be reliable or near end of life?

Or does anyone have a recommendation for a cheap but good inverter or even have one for sale?

My Sunny Boy died 6 months ago, couldn’t see anything repairable inside it, I even phoned up SMA and they said replace it. I then phoned up a solar supplier about 30 miles away they said they could supply a new Sunny Boy as they have one in stock or they could supply a Solis think he said 200 in stock, he said the Sunny Boys don’t sell as they are double the price of the Solis, both with 5 year warranty, similar performance. Roughly £400 for the Solis if I remember correctly.

So by the end of the day I had fitted the Solis and it was up and running. I also bought and fitted the Internet dongo. For some reason the SMA MC4 connectors were slightly different to standard so I had to cut the old ends off and fit a couple of generic MC4 connectors, extra 10 mins work and apart from that no issues.

@roys do you still have your dead Sunny Boy?  If so I would not mind a crack at fixing it and if I can get it going I will give you something for it?

@ProDave, yip Dave still have it, and you are welcome to have a pop at it, it maybe will be a little on the small side for your needs as it was only connected to a 10 panel system. It is a heavy bit of kit, about double the weight of the Solis.

From what I remember the display was totally dead but I was still getting voltages ar the two test points on the PCB. I did a thread on it on the Navitron forum.

As I say you are welcome to have a pop at it.

@roys  I have sent a PM

One option I am looking at is 2 smaller 2kW inverters so if I get another failure I only lose half my generation until it is fixed.

@ProDave

Hi Dave, replied to your pm, yip like plan for using two inverters, mine is / was the 2500hf.

Just out of interest, How would you synch the outputs of are they going onto separate circuits?

roys said:

@ProDave

Just out of interest, How would you synch the outputs of are they going onto separate circuits?

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doesn't matter, they sinc with the grid. They don't seem to take any notice of other inverters outputting high voltages.

Solis is around £400 new with 5 year warranty (can be extended) . I've been fitting these for a few years now, with no issues to date. Solis 2kW is around £220 + VAT. 

binky said:

doesn't matter, they sinc with the grid. They don't seem to take any notice of other inverters outputting high voltages.

Solis is around £400 new with 5 year warranty (can be extended) . I've been fitting these for a few years now, with no issues to date. Solis 2kW is around £220 + VAT. 

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Nice one binky, I am a donkey, of course the mains sensing of the inverter is synching it to the house mains, so it stands to reason that two inverters in the same house would be in synch, obviously typed this morning before my brain was in gear 

roys said:

Nice one binky, I am a donkey, of course the mains sensing of the inverter is synching it to the house mains, so it stands to reason that two inverters in the same house would be in synch, obviously typed this morning before my brain was in gear 

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It's a perfectly reasonable question. I used to wonder if you have a street of houses all with PV, how does the inverter know if the mains grid is 240V if an inverter in another house is exporting to the grid at 245V? I do know from WPD friend that they do get problems with grid voltages rising on estates wth lots of PV in summer months, but I'm kind of guessing the surplus voltages get absorbed by other houses with, say the washing machine working, and I assume modern mains distribution transformers probably monitor the voltages and adjust themselves down accordingly. The DNOs don't like  inverters exporting more than 16A back to the grid, (you can ask for a higher export which may be granted in certain places) and like to limit backfeed to the local transformer to a max of 30% if I remember correctly. On that basis, you still have 70% of the grid to sync with. It's a question I've never got an answer to. 

Update on this, I have just bought a second hand SB3600-TL from ebay.

I am still going to have a go at fixing @roys broken one but I don't hold out much hope.

My own broken one (different make) is completely dead, which you might think is a simple fault like no power getting to the control circuits, but of course there is no service information on any of these not even a circuit diagram and on that one I have literally tested every single visible diode and transistor on the board and not found a fault, and concluded it is probably one of the many legged SMD devices most likely has failed and little chance of ever repairing it.

I dream of how electronics was 30 years ago when most components were big enough to see without a magnifying glass.

I don't know if I mentioned I also have an el cheapo Chinese 600W inverter on a different application which also failed a few months ago, but that had the good grace to go with a proper bang.  I found a pcb mount fuse  literally blown in half, and then 2 power transistors short circuit,  they were easy to find and cheap and that one is working again.

there were issues with the  HF series SMAs, I seem to remember. They didn't seem to be around for very long before being replaced by the TL series. These seem to be pretty robust units - I've only ever replaced units damaged by lighting strikes.

binky said:

there were issues with the  HF series SMAs, I seem to remember. They didn't seem to be around for very long before being replaced by the TL series. These seem to be pretty robust units - I've only ever replaced units damaged by lighting strikes.

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You got me worried there.  But my mistake I have just checked and it's a SB3600-TL-20 that I have just bought.  A private seller upgrading, got it a lot cheaper than the same is being offered second hand by dealers.

shoud be good for 15-20 years. 

I used to look at the cost of the extended warranties. You could get upto 25 years (which was always their claimed design life) . 10 year was around 30% of cost of new (CoN). 10-15 years around 50% CoN 15-20 years was around 75% CoN and 20-25 years was 100% CoN. This gives you some idea of when they expect an inverter to fail. Part of the reason I fit Solis is because they offer warranties extended upto 20 years. Cheaper units tend not to offer that or only 15 years max.

My ebay Sunny Boy arrived yesterday.  Like @roys I found the standard MC4 plugs already on the cables would not fit the SB inverter.  Luckily the SB came with a set of it's own non standard plugs so i had to change them over.  It's all working fine so far.

In other news @roys broken inverter has gone on a magical mystery parcel tour of the UK.  It should have been delivered today.  Last reported tracking it went from Edinburgh to the "north west processing centre" yesterday which Google tells me is in Lancashire, so it's gone the wrong way, and no reported tracking information since so presumably it's still there.

ProDave said:

My ebay Sunny Boy arrived yesterday.  Like @roys I found the standard MC4 plugs already on the cables would not fit the SB inverter.  Luckily the SB came with a set of it's own non standard plugs so i had to change them over.  It's all working fine so far.

In other news @roys broken inverter has gone on a magical mystery parcel tour of the UK.  It should have been delivered today.  Last reported tracking it went from Edinburgh to the "north west processing centre" yesterday which Google tells me is in Lancashire, so it's gone the wrong way, and no reported tracking information since so presumably it's still there.

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Awww my old inverter has gone on a UK tour, glad I used 1/2 roll of packing tape on box so it should take a bit of travel. You never know it might go permanently missing then we can go 50 50 on the postage insurance

It got bored down south and has now reached Inverness.  It might arrive tomorrow as long as they don't lose it again.

SMA use Sunclik connectors - another reason I stopped using SMA, as I hate awkward barstewards! 

ProDave said:

It got bored down south and has now reached Inverness.  It might arrive tomorrow as long as they don't lose it again.

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It's nice to hear Lancashire referred to as "down South". A lot of people we call southerners think that we are somewhere above the Arctic circle.

Geoff1946 said:

It's nice to hear Lancashire referred to as "down South". A lot of people we call southerners think that we are somewhere above the Arctic circle.

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Glasgow is "down south" to me.

ProDave said:

Glasgow is "down south" to me.

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not much isn't 'down south' of Inverness.