Easun SMG II 3.6 kW 24V incorrect PV voltage, no battery charging from PV

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arek
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Easun SMG II 3.6 kW 24V incorrect PV voltage, no battery charging from PV

Post by arek »

Hello,

I'm new to this forum and I'd like to say hello to all.
I bought hybrid inverter marked as Isolar / Easun SMG II 3.6 kW 24V MPPT 500 VDC input from this seller:
https://www.aliexpress.com/item/1005003665606293.html

Unfortunately, there is problem with this unit.
Tried to describe it to seller, but I'm affraid they will not offer any help.
Inverter shows incorrect PV voltage, 120 - 170 V depending switch is ON or OFF. While real voltage from PV panels is about 350 V.
That problem I would leave as I've installed external V and A meters between PV panels and inverter.
There is second, more important problem. Inverter doesn't charge batteries from PV when switch is in ON position. It can draw energy from batteries when solar power is insufficient, but not charge when load is disconnected.
Additionally, it can charge batteries with switch in OFF position :( or when utility power is available.
All parameters are in default values.
I tried to find some information of origin producer, but I'm not sure what I've found.
Do you think, it is easy repairable or I should look for replace board, if they are available?
Or in worse, waste it and look for new one?

Regards
Arek
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coulomb
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Re: Easun SMG II 3.6 kW 24V incorrect PV voltage, no battery charging from PV

Post by coulomb »

arek wrote: Mon, 10 Oct 2022, 20:26 Tried to describe it to seller, but I'm afraid they will not offer any help.
That's the hassle with these cheap on-line suppliers.
Inverter shows incorrect PV voltage, 120 - 170 V depending switch is ON or OFF. While real voltage from PV panels is about 350 V.
That problem I would leave as I've installed external V and A meters between PV panels and inverter.
But if it thinks that the PV voltage is barely at the bottom end of the MPPT range, that may be the reason for reduced charging.
There is second, more important problem. Inverter doesn't charge batteries from PV when switch is in ON position. It can draw energy from batteries when solar power is insufficient, but not charge when load is disconnected.
That sounds like a really bad firmware bug to me, but that's just a wild guess.
All parameters are in default values.
It may be that you need non-default values to charge the battery, though that does sound crazy.
I tried to find some information of origin producer, but I'm not sure what I've found.
It appears to be this one: EASUN POWER 3.6KW Soalr Inverter. That seems to be an Axpert VM II clone, tweaked for 12% more power than the original.
Do you think, it is easy repairable or I should look for replace board, if they are available?
That's so hard to say. My guess is that the hardware will be very similar to that of the Axpert VM II, but there is no schematic trace for the high voltage Solar Charge Controller, which is what you seem to be having the most trouble with.

[ Edit: Had link to the 48 V version. ]
MG ZS EV 2021 April 2021.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
Patching PIP-4048/5048 inverter-chargers.
arek
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Posts: 3
Joined: Mon, 10 Oct 2022, 19:40

Re: Easun SMG II 3.6 kW 24V incorrect PV voltage, no battery charging from PV

Post by arek »

I opened the cabinet. Haven't found any burnt elements or suspicious connections on both sides of PCBs.
Made some photos:
20221120_123215.jpg
20221120_123215.jpg (362.29 KiB) Viewed 68 times
20221120_123209.jpg
20221120_123209.jpg (403.08 KiB) Viewed 68 times
20221120_123154.jpg
20221120_123154.jpg (404.45 KiB) Viewed 68 times
Maybe someone can recognize similar model / type, so I could find more information or spare parts.

I traced two lines that, I think, are used to measure PV voltage, from solar board to board with TMS chip and operational amplifier. They look good.
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coulomb
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Re: Easun SMG II 3.6 kW 24V incorrect PV voltage, no battery charging from PV

Post by coulomb »

arek wrote: Mon, 21 Nov 2022, 19:13 Made some photos:
It looks very clone-ish to me.
Maybe someone can recognize similar model / type, so I could find more information or spare parts.
It doesn't look like anything in my service manuals; the closest was an Axpert VM II. Sadly, none of the Axpert service manuals have much information at all on the MPPT boards.
MG ZS EV 2021 April 2021.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
Patching PIP-4048/5048 inverter-chargers.
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