On sunny days, Inverter switches off when DC voltage gets too high?

[rpdom]

The bit that surprises me is "Amps do not rise above 10.3A on each string, at any time." as I have the same panels (actually I've got the slightly lower rated 385W version) and I've seen over 13A. Yes, I know that's higher than even their rated Isc, but it's what my inverter reports. I might be enough to cause the reported problem.

 

[Ampster]

Yes, I know that's higher than even their rated Isc, but it's what my inverter reports. I might be enough to cause the reported problem.

Could the higher current be a result of colder temperatures? I know the temperature coefficient applies to voltage but perhaps the MPPT is shifting that relationship to cause current to spike. Just a wild ass guess.
EDIT: or as @Solar Guppy suggested, edge of cloud effect.

 

[Hedges]

Maybe I'm having a (another) blonde moment ?‍, but I don't see why this thread is focussing on battery over-voltage when the OP reported the alarms as a "DC input overcurrent fault", which I understood refers to PV DC and not battery DC. He also says the battery reaches 100% at other times of day, without any alarms being raised, so I don't immediately see that (without more data) it being a battery / BMS related issue.

You may be correct, but the error messages may not match actual problem.
Aiming for a lower battery voltage would have current taper off, might allow for a gentle landing before a cell runs up in voltage. The fact inverter is charging to 58V when battery spec calls for 57V may trigger an issue.

<disable one string>

.. would be best to try first.

Each PV string can theoretically exceed maximum operating current of its MPPT.
I was looking to see if the two MPPT could be paralleled, and if the two strings were different orientations, their parallel sum might not exceed the limit. I didn't see that was allowed however.

(Some Sunny Boy have 3 inputs, A & B can be paralleled but C can't.)

If he was having faults below full current, that wouldn't have been the cause.

So cell voltage runners is best guess for now.

 

[Solar Guppy]

On Solis hybrid inverters, DC input overcurrent fault is the PV inputs, has nothing to do with batteries. If I over panel a mppt input ( add a string temporally from a second Solis inverter ) , in partly cloudy weather when the Sun becomes unshaded, I get that message and the inverter goes into fault mode.

The control loops on all Solis inverter takes a few seconds to adjust and can easily put the PV input into a over current condition, never over panel a Solis inverter due to this.

Bottom line is you have to keep current at or under the maximum manufactures specified PV current per mppt input, as edge of cloud events will have panels exceed their nameplate rating, possibly for a minute or two,

 

[Solar Guppy]

Each PV string can theoretically exceed maximum operating current of its MPPT.
I was looking to see if the two MPPT could be paralleled, and if the two strings were different orientations, their parallel sum might not exceed the limit. I didn't see that was allowed however.

On Solis, they are physically independent boost converters, there is no options to gang them.

 

[wattmatters]

a local solar company fitted 23 x Trina Vertex S390W panels in two strings.

Solis 6KW (rhi-6k-48es-5g) Hybrid Inverter

Recommended max PV power 8000w

That's the problem in a nutshell. This is a serious fault caused by the installer and which they need to rectify.

23 x 390 W is nearly 9 kW of PV on an inverter rated for a maximum of 8 kW of PV, and which can only generate 6 kW AC output, with any surplus PV capacity able to be diverted to the battery, provided the battery can accept the charge.

Either:
i. the inverter is undersized for the PV arrays
ii. the PV arrays are oversized for the inverter

The unit is incapable of smoothly managing the transition from battery charging to not charging while the PV is generating a DC power output well above the 6 kW AC output the inverter is capable of.

 

[rpdom]

Could the higher current be a result of colder temperatures? I know the temperature coefficient applies to voltage but perhaps the MPPT is shifting that relationship to cause current to spike. Just a wild ass guess.
EDIT: or as @Solar Guppy suggested, edge of cloud effect.

That's what I would have expected, but no cloud at the time and the temperature wasn't particularly cool. I don't have sensors on the panels, so I can't tell what they were, but outside ambient was around 19°C, just a few degrees below the rating temperature.

PV output for my 8x385W 3.08kW array peaked at 4.06kW.

 

[SeaGal]

That's the problem in a nutshell. This is a serious fault caused by the installer and which they need to rectify.

23 x 390 W is nearly 9 kW of PV on an inverter rated for a maximum of 8 kW of PV, and which can only generate 6 kW AC output, with any surplus PV capacity able to be diverted to the battery, provided the battery can accept the charge.

Either:
i. the inverter is undersized for the PV arrays
ii. the PV arrays are oversized for the inverter

The unit is incapable of smoothly managing the transition from battery charging to not charging while the PV is generating a DC power output well above the 6 kW AC output the inverter is capable of.

I think I said all that on Friday (https://diysolarforum.com/threads/o...en-dc-voltage-gets-too-high.63521/post-795101) but good to repeat it.. hope the OP appears again sometime!

 

[GOM BOF]

Solis have been in touch. They have loaded new firmware onto the system which they think will solve the problem and have asked me to monitor things and get back to them if any problems occur.

 

[SeaGal]

Fingers crossed. Please keep us updated and let us know which firmware version was loaded.

 

[GOM BOF]

Now showing as "Inverter Version 470044-010000"

 

[rpdom]

Now showing as "Inverter Version 470044-010000"

470044 is the latest firmware for the RHI-xK-48ES-5G series. That what my old one was upgraded to.

 

[GOM BOF]

The new firmware has been in place for just over a week. The last week has been a very sunny period and I would have expected the system to be alarming and resetting at least once every day. I am pleased to say that there have been no alarms or incidents since the new firmware went in.