Hi all,

I've had a cascade of failures in the form of Infinisolar 10kW inverters failing at a single installation site. Any assistance, input and/or advice will be much appreciated towards troubleshooting and identifying the cause of the failures.

Setup: 

2 identical systems serving 2 buildings.

Each system consists of:

• 3 x Infinisolar 10kW inverters setup for parallel output
• Approximate 8.5kWp array per inverter
• FreedomWon 80/56 Lithium-ion battery

The system was commissioned in November 2017.

• The first inverter failed on the 25th of May and was found dead on site
• The next 4 inverters failed successively over the next month, two displayed error E7, one displayed error E3 and the other was found in a constant state of rebooting
• One inverter remains and is operating in grid-tie mode only

After opening the inverters we have found that each and every inverter has clear but varying degrees of damage to the BOOST module on the DC-DC board and will certainly require replacement of the board. Some inverters showed signs of damage to the Main Board too.

We have obviously referred the issue to the supplier, who is assisting us somewhat but is unfortunately technically incompetent and unable to diagnose the cause. I understand there may be a lot more information required to make any conclusive findings regarding a single cause, but let's start it off here.

Does anybody have an idea of what could have caused a cascade failure such as this? 

Is anybody familiar with the failure modes of the Infinisolar 10kW - E7 and E3?

 

Thanks in advance,

Nicholas

 

Hi Nicholas,

I'm not an expert but I've experienced E7 (relay fault) in these two cases:

1) Grid power was applied first, inverter started, then battery was connected. Error 7 was generated immediatelly.

2) Battery was connected, then PV switch was turned on, and grid was turned on just right after that. The result was Error 7.

In both cases the hard shutdown and restart in the correct order solved the issue. So, the battery first, then PV switch on, and grid on as a last step, after a minute or two.

 

I can't speak for your setup, but if the FreedomWon battery is able to disconnect/reconnect itself automatically, then this could cause E7 for sure. There are quite fat capacitors on the battery side of Infini, so every re-connection of the battery creates a nice huge shock to these caps...and to the DC board too. Originally, Infini was designed to work with Lead Acid, so nobody took possible smart BMS effects into account, as LA+BMS combination is a rare animal. As of today, there's a function in SolarPower called "Activate li-fe battery". AFAIK, it has nothing to do with equalize, but when activated it slowly charges capacitors first, allowing you to connect a li-fe battery without any sparks then.

So, my 2cents: FreedomWon smart BMS disconnected the battery couple of times, in order to protect the cells for some reason and this re-connection caused gradual destruction of all the units.

What do you think? Is it possible?

An excellent theory. I use pre-charge with a single 4 kW Axpert, let alone three 10 kW inverters in parallel. It costs a high surge power resistor, and a smallish DC rated contactor. The money seems well spent to me, but I never seem to hear pre-charge discussed. 

1 hour ago, Coulomb said:

high surge power resistor, and a smallish DC rated contactor

One method I heard of is to use an incandescent lamp of some kind, maybe two 24V truck ones or similar. Connect that between the inverter and battery. This causes a slow charge of the capacitors via the lamp and when the lamp starts to go dim (or you can also monitor the voltages on the capacitor side) you take the lamp out and connect it directly. Less surge current that way.

Of course this does not deal with the issue where a BMS might disconnect you, and causing a surge current on reconnection. For that you may well use a precharge circuit, I assume you have some kind of timer or control circuit that decides when to close the contactor?

Of course this is speculation, and it does not answer the main question: Which is where to find someone worth their salt to fix these things.

Yeah, I'm using the lamp workaround too, as I was reluctant to spend money on a decent resistor. One 230V 24W lamp per inverter is perfect. Connected it paralell to the DC fuse and the power on sequence is like this:

• connect lamp, it starts to glow
• wait couple of seconds, lamp starts to go dim
• close the fuse
• disconnect the lamp

But just like Plonkster noted, this works only for manual opeation. If the BMS is fiddling with the battery on its own, some other workaround must be implemented. Not mentioning, that if BMS really does, then there's something bad going on (over current maybe?).

@Nicholas, can you check the BMS log files for any suspicious activity? Or ask FreedomWon tech support, maybe?

16 hours ago, Youda said:

Hi Nicholas,

I'm not an expert but I've experienced E7 (relay fault) in these two cases:

1) Grid power was applied first, inverter started, then battery was connected. Error 7 was generated immediatelly.

2) Battery was connected, then PV switch was turned on, and grid was turned on just right after that. The result was Error 7.

In both cases the hard shutdown and restart in the correct order solved the issue. So, the battery first, then PV switch on, and grid on as a last step, after a minute or two.

 

I can't speak for your setup, but if the FreedomWon battery is able to disconnect/reconnect itself automatically, then this could cause E7 for sure. There are quite fat capacitors on the battery side of Infini, so every re-connection of the battery creates a nice huge shock to these caps...and to the DC board too. Originally, Infini was designed to work with Lead Acid, so nobody took possible smart BMS effects into account, as LA+BMS combination is a rare animal. As of today, there's a function in SolarPower called "Activate li-fe battery". AFAIK, it has nothing to do with equalize, but when activated it slowly charges capacitors first, allowing you to connect a li-fe battery without any sparks then.

So, my 2cents: FreedomWon smart BMS disconnected the battery couple of times, in order to protect the cells for some reason and this re-connection caused gradual destruction of all the units.

What do you think? Is it possible?

Thank you for the input and hypothesis. It is certainly worth interrogating further. 

My immediate thoughts lead me to believe that we would see damage to the capacitors on the battery side, if the BMS was causing sudden and frequent disconnects and reconnects. None of the inverters that I have opened shows any visible signs of damage to the capacitors - I'd expect to see rupture at the relief marks of the capacitor or black burn marks around the capacitor and surrounding components, nothing like that is evident.

I am not an electronic engineer and therefore cannot discard that theory, but those are my thoughts.

With regards to the "Activate LiFe battery" in SolarPower, I briefly remember reading somewhere that the inverter sends a high voltage DC pulse "Start-signal" to start/initiate/wake-up the batteries, in the order of 60VDC I believe. I have used this before when working with the Infinisolar and lithium-ion battery packs. Instead of having to manually switch on the batteries, the inverter performs this function with the "Start-signal" - again, this is just my understanding.

I'd like to post a couple images here of the damage seen to the DC-DC boards, specifically the BOOST modules - perhaps that will allow for a better understanding and some additional hypotheses.

6 hours ago, plonkster said:

Of course this is speculation, and it does not answer the main question: Which is where to find someone worth their salt to fix these things.

1

That's exactly it. Unfortunately, our supplier has demonstrated that they lack the technical competence to provide any input on either diagnosing the cause of the problem and subsequently validating or invalidating the warranty, or providing any kind of comprehensive report regarding the findings of the damaged inverters. 

Nonetheless, we are working through the problems and our frustrations with the supplier.

Any Tom, Dick or Harry with a mild degree of technical competence can change boards in an inverter and call themselves an inverter repair technician, but to find somebody that can actually evaluate the damage and its root cause, down to an elementary component level, is NOT any Tom, Dick or Harry.

5 hours ago, Youda said:

@Nicholas, can you check the BMS log files for any suspicious activity? Or ask FreedomWon tech support, maybe?

 

We have connected to the one FreedomWon unit and accessed the logs (I still need to pull the logs from the other unit).

Two historic trouble codes were recorded:

1. P0A06 - Charge Limit Enforcement Fault
2. P0A08 - Charger Safety Relay Fault

Unfortunately, I was not able to interrogate whether these historic faults codes had any time stamps related to their occurrence. 

I have been reading through the OrionBMS utility help manual describing the DTC fault codes, but I am still uncertain whether this historic event is directly related to the cascade failure of the inverters or is simply a red herring related to the commissioning process.

 

We've experienced further failures of the Infinisolar 10kW inverter, at different installation sites. 

The machines all failed quite catastrophically - usually blowing the DC-DC board. 

We have deduced that the failures seem to be attributed to a specific batch of inverters. 

The effected serial numbers translate into a manufacturer date of between February and April of 2017. 

e.g. 96161702.... Up to 96161704 

The machines we purchased were of the model description: "InfiniSolar 10k-PAR-B"

We strongly believe that the failures are a result of a manufacturing or design defect present in the machines produced between the aforementioned date range. 

We have raised the problem with our supplier and are hoping that they will invoke action from Voltronic Power. 

The last and final inverter (Inverter number 6) has failed at our commercial site. 

This inverter was left configured in Grid-Tied only mode, as opposed to Grid-Tie with Backup (2) and Battery charging.

The inverter could no longer see the PV array/string on MPPT1. MPPT2 was still functional though. We suspect the failure/damage has been restricted to the BOOST module due to the revised configuration which resulted in no battery being connected and no battery charging taking place. We have yet to have the inverter inspected by our supplier and will only be able to confirm the damaged components after evaluation.

From the damage seen on the other inverters (BOOST module 1 - MPPT1), we suspect the problem originates in the BOOST module(s) of the inverter, with a tendency to show a failure on MPPT1 and not MPPT2.

On 2018/07/20 at 3:32 PM, Nicholas said:

That's exactly it. Unfortunately, our supplier has demonstrated that they lack the technical competence to provide any input on either diagnosing the cause of the problem and subsequently validating or invalidating the warranty, or providing any kind of comprehensive report regarding the findings of the damaged inverters. 

Nonetheless, we are working through the problems and our frustrations with the supplier.

Any Tom, Dick or Harry with a mild degree of technical competence can change boards in an inverter and call themselves an inverter repair technician, but to find somebody that can actually evaluate the damage and its root cause, down to an elementary component level, is NOT any Tom, Dick or Harry.

@Nicholas

Hi Nicholas

I have experienced exactly the same problem with a set of 3 Infini's linked in parallel.

What was the outcome of yours? Repaired and if so where?

Will appreciate any help.

Hi Chris, I think this Swedish guy daromer on secondlifestorage has blown his Infini 10 as well and repaired it himself. He made a video on it as well. Hope this helps.

Rik