Two parallel EASUN 8KW/Voltronic Axpert Shorted

[pawpro]

Hi I just installed a second identical (consulted with seller) EASUN Axpert 8KW in parallel yesterday. The first one was working like a charm for 6 months. I have 2 JBD BMSs behind a 250A resettable fuse. Today during the day and modest solar production (9kw across 4 strings) the 250A fuse tripped and the power was cut. I went to check and both inverters were dark/dead. No smoke or smell. I tried turning resetting the fuse couple of times but it tripped each time. I then measured 0.16-0.19ohm on input to both inverters. Tried connecting both via 8ohm 50w to charge up but they would just continuously consume the power afforded by the resistor and never charge. It seems that both inverters are shorting their respective battery terminals.
I cannot wrap my head around how two of them failed at the same time and why both failed the same way. I would have imagined even if one shorted the other one would trip or something. But it seems both are dead and both are shorted. This is an off-grid installation so I am not looking forward to the next few days. Any ideas/thoughts ??? I am quite acquainted with a soldering iron or a scope

The bloody irony is I bought the second one to increase reliability in case the original one failed. Day later I am with no power...

 

[Mattb4]

Hard to say without being able to see the installation where the fault might originate. However a few things come to mind.
What do you mean by fuses tripped? Fuses blow and can not be reset. If it is instead a breaker it could be bad. There are a few real dodgy DC breakers out there.
Is it possible your BMS is tripped? What voltage do you read at battery output?
Have you tried just energizing one without the second in parallel and no connecting communication cable?

It could be both units are toast because they tried to parallel out of phase.

 

[pawpro]

So you think an AC synchronisation fault fried them? Interesting. Yeah I meant a 250A DC breaker. Both BMSs go into short circuit protection at the same time every time after the breaker already tripped but only if either (or both) inverters are connected. I believe the BMSs behave correctly. The short is clearly present on both inverters' battery terminals.

I need to act fast and do some damage control. I am considering buying a third and running it while the seller tries to blame me and themselves out of this problem. I considered my options for 48v hybrid inverter for 8kW+ and this one really seemed to check the boxes especially the claims of up to 9 units in parallel.

I did ask the seller to advise me which inverter to buy (to parallel). Maybe they send me one with different FW one that behaves differently in some way causing this problem.

Any suggestions what to buy if I were to reconsider the brand? I am in EU. I need few more months of an off-grid setup, backed by 48v LFP bank, 12kW of solar and generator for cloudy days.

I disconnected the current sharing and comms cables but obviously and sadly it changes nothing. The short persists.

 

[Offshore]

I have Easun 2pcs inverters parallel, this is my second set of parallel inverters Easun and never had problems.
Easun uses Voltronic or Sorotec inverters, they just put stickers, and brands.
Communication with Easun will take a long time for the warranty.

I have 2 x 5.5kw and work fine ,my PV is 7kw 4.4klw +2.6kw2
https://www.easunpower.com/products/solar-inverter-500vdc-5500w-pv-input-230vac-48v

Believe you are with
https://www.easunpower.com/products...r-500v-solar-charge-controller-built--in-wifi