Solax SK_SU3700E inverter

[Barge17]

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Having failed to get this invertor talking to my Darfon BMS https://camelot-forum.co.uk/phpBB3/view ... 480#p49480, I had 3,480 kWp solar fitted on a big shed (435W each x 8) last week and connected them in two strings 1 West and 1 East facing for comparision before potentially increasing the number of panels on the most efective side.

I have not yet got the remote monitoring sorted, but have got a LAN cable from my router connected to it in readiness. Not impessed with the SolaxCloud so far though.

The invertor display panel has shown the voltages from the panels soon after booting up, but after a while the display freezes and is not responive to button presses. I wonder if the thing is economically repairable or is it time to think about a replacement? Or is it just "finger trouble" on my part?
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[Barge17]

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It seems to be fairly consistent, When the DC, the panels and lastly the mains are all connected, there are a few relay clicks from within, then the display buttons work and the setting can be changed after entering the Pass key and solar powers are shown on screen for half an hour or so, then it feezes up, often with the screen below:
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[Stinsy]

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It seems to be fairly consistent, When the DC, the panels and lastly the mains are all connected, there are a few relay clicks from within, then the display buttons work and the setting can be changed after entering the Pass key and solar powers are shown on screen for half an hour or so, then it feezes up, often with the screen below:
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Sounds like an overheating transistor. Do you have a thermal imaging camera? Failing that the old school method is to pick a suspected transistor and give it a bast with an upturned can of air duster every few seconds. If it works in that situation, swap out the transistor.

[Barge17]

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"Do you have a thermal imaging camera" - no. but I know a man that does! Thanks for that, we'll give it a go.

Cheers
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[Barge17]

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Ive got the loan of a flir phone attached camera, and opened up the box whilst its try ing to run. The bright spots at the left are multi-pin ICs

This is the sequence of events in daytime, nothing happens at all when there is no power from the sun:


0sec - Grid switched on
13 sec - Click fron Panel input relay
25sec - off/on/off again
46 sec - Solar circuits fans start on top of inverter
1minute - repeated clicks from central relay
1.22 - RH fan on
1min 26sec - heavy click from battery relay
1.30 - green led on battery comes on
1min60 - Another heavy battery relay click
2.14 - battery led goes red
2.20 - silence + no battery led

So now I need to know where to look for the suspected transistor. Fascinating stuff?
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[Stinsy]

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Ive got the loan of a flir phone attached camera, and opened up the box whilst its try ing to run. The bright spots at the left are multi-pin ICs

This is the sequence of events in daytime, nothing happens at all when there is no power from the sun:


0sec - Grid switched on
13 sec - Click fron Panel input relay
25sec - off/on/off again
46 sec - Solar circuits fans start on top of inverter
1minute - repeated clicks from central relay
1.22 - RH fan on
1min 26sec - heavy click from battery relay
1.30 - green led on battery comes on
1min60 - Another heavy battery relay click
2.14 - battery led goes red
2.20 - silence + no battery led

So now I need to know where to look for the suspected transistor. Fascinating stuff?
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It sounds to me as if there is a problem with the SMPS that supplies ELV DC power to the control electronics. My guess is that the big battery relay pulls a chunk of power and triggers the SMPS to give up. First job is to locate the SMPS. Is that it top right on the PCB? Or is it separate?

Next thing I'd do is isolate the SMPS and provide power to the control circuit from an alternative power supply (eg a battery or benchtop power supply). If it works in that condition, you've located the problem. SMPS are simple devices, and easy to fix. You basically have a transformer, transistor and a bunch of resistors, diodes, and capacitors. Most of it is super-reliable however the transistor might be failing, this is an easy fix. Alternatively the solder might have failed on the transformer contacts, this is easy to fix too.

If the SMPS is fine then the next likely problem is the battery contactor itself...

[Barge17]

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Thanks for that, Stinsy, plenty to go at now, but it will be next week before I am back at it.
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