48V 280Ah DIY battery

[brum]

Not yet. I'll think about it for a couple of days.

The BMS will cut the discharge path at 150A. The fuse will work at 150A for several minutes (if we accept that it was a genuine fuse). To be above 150A the only option seems to be a short circuit. And a short circuit would leave some marks. If it was the inverter, then it would not be working fine after that.

I'll look at the old logs to confirm that this is an exceptional case. I'll look also at the documentation for details on the event. Since this was like 5 minutes before the fuse failure I have some doubts that it is related. The event timestamps between the two systems have always been 1:1 till now, so I'm considering them correct. And I see no issues reported from the BMS (like spikes).

 

[brum]

So one or other way I'll go through the SMA support. The inverter failed today. As it was working just fine suddenly popped up a Fault/Island Grid error. 2 hours later I saw increased gird consumption, found out the error and a disconnected circuit breaker. The surge protection devices were fine, the RCD was also fine.

Let's see what the SMA support will say on the problem. I'll share details once I have such. I hope that the tier 1 equipment support will be smooth.

 

[brum]

False alarm. The inverter is fine. It has gone into some error mode due to AC overvoltage. I suspect that this was related to a storm that was going on around the time when the error has triggered.

The short on the AC2 out was due to a relay staying on. The relay is between the transformer and the AC. A toroidal transformer is drawing massive current when initially connected. I recall doing a pre-charge circuit for a 300W transformer that was tripping a 16A breaker 15 years ago. The inverter is capable of more than a 5kW peak, so its transformer is 3+kW. This can easily trip the 20A/B breaker that is in front of the inverter.

The short was gone after the inverter stayed off for some time. And I started building up the puzzle. The chain of events is something similar to that:
1) AC overvoltage (reason unknown, but possibly due to a thunderstorm that has not burned out any of the surge protectors). Inverter showed error 1707 - AC1 overvoltage.
2) Inverter goes into some fault mode saying it is in island mode but was not producing power. Despite that, it kept the transformer connected.
3) Restart of the inverter (shutdown procedure, disconnecting the AC side, disconnecting the DC side) has resulted in the inverter being in an off state, but the relay between the transformer and the AC stays on. Probably a firmware bug or design flaw.
4) Once I tried to connect the AC side the breaker tripped. There is a massive toroidal transformer that is not energized and is being directly connected to the AC. This probably can bring down the 63A main breaker too.
5) Due to the relay being connected, the AC side showed a short circuit (or almost a short circuit).
6) After being off for some time the relay has reset to off state. How - now idea. But after a few hours, everything works fine again.

And now on the bug/design flaw - it would be impossible to reconnect the AC side with the relay being in that state. When the inverter is on and is connecting the grid it first syncs the output to the grid and then connects the AC side. In an off-grid setup, the inverter starts first, so it would not be an issue.

 

[brum]

So this is getting stranger ant stranger. There is regular flow when the battery gets full, the inverter starts to discharge it and after a few seconds there is voltage spike according to the inverter.

From what I see the spikes are to over 65V in some cases and when this happens the inverter goes in failure mode.

Here are the logs from yesterday. The inverter was charging, the SOC was going up, it got to 100% and shortly after that the inverter stopped charging. Then it started discharging, the battery voltage measured by the inverter was 56.7V - 56.8V, the voltage was dropping to 56.3 and there was a spike of 61.2V for 3 seconds. Than back to 56.2V and a few seconds later a spike to 65.2V. Shortly after that the inverter goes in fault mode and the battery voltage is 55.7V.

 

[houseofancients]

So this is getting stranger ant stranger. There is regular flow when the battery gets full, the inverter starts to discharge it and after a few seconds there is voltage spike according to the inverter.

From what I see the spikes are to over 65V in some cases and when this happens the inverter goes in failure mode.

Here are the logs from yesterday. The inverter was charging, the SOC was going up, it got to 100% and shortly after that the inverter stopped charging. Then it started discharging, the battery voltage measured by the inverter was 56.7V - 56.8V, the voltage was dropping to 56.3 and there was a spike of 61.2V for 3 seconds. Than back to 56.2V and a few seconds later a spike to 65.2V. Shortly after that the inverter goes in fault mode and the battery voltage is 55.7V.

are you using voltage on your inverter, or actual communication ( not sure if that is even possible on a sunnyisland)

 

[brum]

Actual communication. The inverter is using lithium battery and is getting the SOC from the BMS. The BMS is Seplos 150A, last generation.

 

[brum]

The issue was solved (likely). The BMS settings were kind of incorrect. I've listed the settings and the charging algorithm that was reversed engineered here - https://diysolarforum.com/threads/seplos-can-bus-rs485-48v-200a-8s-16s-bms.20051/post-790692 .

 

[shingsam]

So this is getting stranger ant stranger. There is regular flow when the battery gets full, the inverter starts to discharge it and after a few seconds there is voltage spike according to the inverter.

From what I see the spikes are to over 65V in some cases and when this happens the inverter goes in failure mode.

Here are the logs from yesterday. The inverter was charging, the SOC was going up, it got to 100% and shortly after that the inverter stopped charging. Then it started discharging, the battery voltage measured by the inverter was 56.7V - 56.8V, the voltage was dropping to 56.3 and there was a spike of 61.2V for 3 seconds. Than back to 56.2V and a few seconds later a spike to 65.2V. Shortly after that the inverter goes in fault mode and the battery voltage is 55.7V.

Same case with me, i use battery lifepo4 15s, and i use mode VRLA 46V. They can spike up to 60V
Has your problem been solved? If so, what settings did you change?

 

[brum]

Yes, it is solved. The BMS should not disconnect the charging path. If it does - find out why and fix it. If it doesn't - there is no reason for such voltage spikes.

 

[shingsam]

Yes, it is solved. The BMS should not disconnect the charging path. If it does - find out why and fix it. If it doesn't - there is no reason for such voltage spikes.

Ok i know, can u please share parameters for charger?

 

[brum]

Do you have a Sepols BMS? If yes - check https://diysolarforum.com/threads/seplos-can-bus-rs485-48v-200a-8s-16s-bms.20051/post-790692. If not - open a separate thread for your issues and I'll try to help.

 

[shingsam]

Do you have a Sepols BMS? If yes - check https://diysolarforum.com/threads/seplos-can-bus-rs485-48v-200a-8s-16s-bms.20051/post-790692. If not - open a separate thread for your issues and I'll try to help.

No, i dnt use seplos bms. I use battery from Hua*ei.

 

[brum]

Well, open a thread, provide your current setup and configuration and people here will likely help. I'll also try to spot a problem in your setup. But this thread and your problem have close to nothing in common.