Axpert: Fluctuating Error 83

[CDL]

Hi guys, I have an ongoing problem with a pair of Axpert inverters that I have had installed and I am hoping that someone can point me in the right direction for a solution.

The installation was done by an installer but they seem to be as stumped by the problem as anybody else is. The basic details of the installation are as follows:

• 28 335w Canadian Solar panels in two strings of 14 each.
• 2x Axpert inverters set up in a "master-slave" relationship.
• Two x 10.2 kW Revov second life batteries, each with its own BMS.

The problem seems to have a pattern which is as follows:

• Typically the batteries are either fully charged or very close to full charge.
• There will be little to no load on the system.
• it only occurs during the day when the panels are pushing out a great deal of power (let us say in the order of 40 A to 43 A per inverter).
• A voltage discrepancy arises between the inverters. one of them will typically show 54 point something V and the other one as much as 64 point something V.
• The slave inverter will then default to an error 83 and throw up a red light.
• If I switch on something that creates a load, then the voltage drops and the two inverters start working properly again. Take the load away and the problem pops up again.
• If one keeps the system without load, what will also often happen is that the error 83 will pop up as the voltage rises above 64 V and then as the voltage drops again, the error will go away. This site will continue repeating itself either until load is placed on the system or panel output reduces towards the end of the day as the sunlight fades.

Another problem that we have had recently – and I do not know whether this is related – is that when we ran the batteries down overnight (they are set to cut over to utility at 48 V), the one unit showed voltage as low as 34 point something and the BMS shutdown altogether – no lights. The other battery was showing something more than 51 V and the BMS was still working fine. The battery installer has since been across and fitted a comms cable between the two BMS units. I have not yet had an opportunity to ascertain whether the foregoing problem has been fully resolved or not. But I mentioning it for the sake of completeness.

Does anybody have any ideas? All input much appreciated.

 

[Youda]

To me it looks like you have batteries separated. One battery connected to the 1st Axpert, other battery connected to 2nd Axpert.

The correct parallel setup is, that batteries shoud be wired in parallel and both Axperts should share this single battery bank.
Can you check how are your batteries wired?

 

This is how it should be connected:

Edited May 11, 2019 by Youda

[CDL]

Thank you Youda. It seems to be quite clear just from the LCD displays that each inverter is seeing a separate battery array. I would have to open trunking to trace the wiring.

Edited May 11, 2019 by CDL

[PaulinNorthcliff]

I'd also be concerned that 14 panels per string is severally over the 120V input limit for each Axpert.

[Youda]

1 hour ago, CDL said:

Thank you Youda. It seems to be quite clear just from the LCD displays that each inverter is seeing a separate battery array. I would have to open trunking to trace the wiring.

Well, then tell your installer to fix it for you.
It's crucial that the battery bank have to be shared by the both inverters.

Here's the parallel guide for your installer to reference: http://www.mppsolar.com/manual/PIP-MG (PF1.0)/PIP-HS_MS Parallel Guide (9-units).pdf

[Youda]

25 minutes ago, PaulinNorthcliff said:

I'd also be concerned that 14 panels per string is severally over the 120V input limit for each Axpert.

It depends on what's the exact Axpert model. Some models have 145 VoC, others 450 VoC.

2nd option is, that these "14 panels strings" are not real the serial string, but maybe a 7 panels wired 2x in parallel. Clearly, @CDL does not know what exactly his installer did...

[CDL]

11 hours ago, Youda said:

It depends on what's the exact Axpert model. Some models have 145 VoC, others 450 VoC.

2nd option is, that these "14 panels strings" are not real the serial string, but maybe a 7 panels wired 2x in parallel. Clearly, @CDL does not know what exactly his installer did...

Quite correct. I only know that 14 panels serve one inverter.

[CDL]

12 hours ago, Youda said:

Well, then tell your installer to fix it for you.
It's crucial that the battery bank have to be shared by the both inverters.

Here's the parallel guide for your installer to reference: http://www.mppsolar.com/manual/PIP-MG (PF1.0)/PIP-HS_MS Parallel Guide (9-units).pdf

Thank you. I found this too yesterday: https://www.thesunpays.co.za/ManualParallel-installation-MKS-4Kva and 5kva.pdf

See item 5 which speaks directly to the issue and reads:

5. Battery Connection WARNING! Be sure that all inverters will share the same sets of batteries. Otherwise, the inverters will transfer to fault mode. WARNING: Be sure the length of all battery cables is the same. Otherwise, there will be voltage difference between inverter and battery to cause parallel inverters not working. Follow below chart to connect batteries. All battery cables are connected from inverters to batteries via the same BUS bar.

I opened the trunking up and couldn't find a busbar. Unless its behind the DC DB, which seems unlikely.