Solaredge optimiser testing

[Dillsue]

Hi. Has anyone any experience of optimiser testing? Ive picked up 10 unused but "shop soiled" P350s off ebay and want to check they are all good before installing on the roof. Ive got a 4kw solar edge inverter and a single 245w solar panel. I can get individual optimisers to pair with the inverter when the panel is connected and powering the optimiser but I dont see any generation after pairing. The data sheet says each string should have a minimum of 8 optimisers so I assume this is the problem. I dont have access to 8 panels at the moment so am wondering if theres any other way to fully test them??

[TonyT]

What’s the minimum string voltage for the inverter?

[Conor]

Plug each optimiser in turn to the panel and make sure you get the nominal 1volt at the cables before the inverter. A basic check but the first one to do.

Edited January 9, 2022 by Conor

[Dillsue]

The inverter datasheet gives a max input of 500vdc, a nominal input of 350vdc but no minimum. The optimisers output is max 60vdc, so way short of 350 and I guess thats the reason for needing a minimum of 8 on a string. Just trying to see if theres another way to test without buying another 7 panels.

[Dillsue]

7 minutes ago, Conor said:

Plug each optimiser in turn to the panel and make sure you get the nominal 1volt at the cables before the inverter. A basic check but the dors tone to do.

Will check that, as coupled with being able to pair with the inverter it gives a bit more confidence but would ideally like to see some power coming through them.

[billt]

FWIW the SE1000/1500/2000 have an input voltage range of 75-480, maximum 500. I think you'll need more panels.

[Dillsue]

22 hours ago, billt said:

FWIW the SE1000/1500/2000 have an input voltage range of 75-480, maximum 500. I think you'll need more panels.

I think your right and more panels are needed. Wasnt planning on buying the panels just yet but might have to rethink!!

 

Thanks for all the replies

[TonyT]

Variac for testing purposes with bridge rectifier?

[Dillsue]

20 hours ago, TonyT said:

Variac for testing purposes with bridge rectifier?

I think I would need 7 of them to power the minimum of 8 optimisers incl one optimiser powered by the panel I have.

 

A bit of research reveals solaredge produce a unit to disable the safe 1vdc output so the optimisers can be connected to non solaredge inverters. It maybe possible to test individual optimisers this way but Id need to buy the disabling tool and then buy another inverter that would accept the low input from a single optimiser, if such a thing exists.

 

Probably going to leave the testing until I buy the panels and take the chance Ive not been sold a set of duff units!!

[Radian]

Solaredge  say "As long as the power optimizers are not connected to the inverter or the inverter is turned OFF, each power optimizer will output a safe voltage of 1V."

So how does the optimiser 'know' it's not connected? (excuse my ignorance but I think you should be able to hack around this problem with a few clues).

 

Presumably the optimiser's output current sense is used to inhibit the MPPT logic. If this is the case then applying a suitable load should get it to operate. Guessing that your 245W panel has Vmp of, say, 44V then you would want a load current of 245/44  = 5.57A So a resistor of 44/5.57 = 8 Ohms would present the optimal load. That might be a bit tricky as a dummy load sinking 245W (loudspeaker was my initial reaction!) but a couple of 3kW kettle or immersion heater elements (240V/13A=18 Ohm) in parallel would give you an idea of whether the MPPT function was operating. A multimeter would be able to confirm your load resistance of around 9 Ohms, and show if around 5A was flowing.

[SteamyTea]

Maybe this is a dumb question, but do you actually need optimisers?

 

[Radian]

34 minutes ago, SteamyTea said:

Maybe this is a dumb question, but do you actually need optimisers?

 

 

Most if not all inverters use MPPT per string input but I think outboard optimisers can compensate within a string to get around partial shading. I'm not a PV user though so I may stand to be corrected.

 

Also, thinking about the testing suggestion I made earlier, it occurred to me that I would be possible for back-channel comms between the invertor and optimisers on the DC connections (when I asked how they might know if they were connected) if the signal was AC coupled. I'm doubtful that this would be the case but it might explain why Solaredge sell an adaptor designed to allow their optimisers to work with other makes of invertor. That bit was what got me thinking.

[SteamyTea]

41 minutes ago, Radian said:

Most if not all inverters use MPPT per string input but I think outboard optimisers can compensate within a string to get around partial shading. I'm not a PV user though so I may stand to be corrected.

Yes, they are of use when shading is a problem.

But as this is an, as yet, uninstalled system, on a new roof, I was wondering if shading was going to be a problem.

 

 

Edited January 11, 2022 by SteamyTea

[Dillsue]

Theres data transfer between the inverter and the optimisers to gather status and generation info for each module/optimiser so I guess theres also data sent from the inverter to activate the optimisers??

 

Youre right about optimisers dealing with shading that may otherwise pull down the output of the entire string, but they will also help if one module is dirty say with the output from a seagull, or theres a film of dirt over one end of the array, or a module is faulty. Another big benefit is the module level monitoring you get via the solaredge web site. We had a module embedded optimiser fail a couple of years ago and without the monitoring feature it may have taken years to spot the small drop in output. Even if we had spotted it, without the monitoring fault finding would have meant lifting individual modules to find the duff one, potentially 16 modules being lifted!! Im a big fan of SE:)

[Radian]

1 minute ago, Dillsue said:

Theres data transfer between the inverter and the optimisers to gather status and generation info for each module/optimiser so I guess theres also data sent from the inverter to activate the optimisers??

 

OK, right, I couldn't spot any cabling other than PV in/out when I looked at the datasheet. Does this then mean there's an ID on each optimiser or maybe the discovery is performed using a unique MAC address per device?

[Dillsue]

The optimisers have serial numbers and you log the postion of each serial number during install then upload it to solaredge and they replicate the layout on their web site.  The inverter collects generation data from each optimiser and passes it to the web site where its displayed. I assume the inverter communicates using the serial numbers as theres no manual addressing to be done. Its all done over the DC cabling. All clever and useful stuff

Edited January 11, 2022 by Dillsue

[Radian]

1 minute ago, Dillsue said:

All clever and useful stuff

 

Until you want to do some basic module testing ?

 

[SteamyTea]

29 minutes ago, Dillsue said:

All clever and useful stuff

Most people are fascinated by PV generation for the first few weeks, then get on with life.

Most inverters log the data, some even have Bluetooth built in and you view via a simple application on you phone/PC.

 

To be honest, if you do not have a shading issue, don't bother with them.  Sell them on eBay.

[Dillsue]

12 hours ago, SteamyTea said:

To be honest, if you do not have a shading issue, don't bother with them.  Sell them on eBay.

If youre sure theres no shading then thats a consideration but how do you stop neighbours trees growing, passing clouds, seagull s**t, a bit of algal growth one end of the array, all contributing to shading in varying degrees. All I can say is that our SE system has significantly beat the forecast generation every year since weve had them despite us having some chimney shading that wasnt considered in the forecast figure?