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Huber (Axpert clon?) 5 kW inverter stops accepting full solar input


Álvaro
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Hello everyone.

This is Álvaro, writing his first post from a sunny La Mancha, in Spain. I spent some time reading posts to see if my issue had already been covered, but failed to find anything related.

I live off-grid: a 3+3 array of 320 W panels, a 5.2 kWh LiFePO4 Energy Storage Pack battery and a so-called Huber 5 kW inverter/charger which I understand is some kind of Axpert clon (label below).

In normal sunny days, the inverter used to allow in 30+ A from the panel array in the morning, with a half-empty battery. This seems consistent with the solar array capabilities. I am not sure when it started to happen, but now the inverter is not allowing this much power in anymore, and generally allows only up to some 13 A, even in clear sunny days. It does charge, and there are no failure warnings or anything: it just does not charge as much as it should.

A potential involvement of the solar array can be discarded --no spots, no clouds, no leaves, no bird poop or anything. This suboptimal charge happens in full sun, with mild ambient temperatures around 15-25 °C, and with a non-full battery.

And here comes the funny thing. I have been away from home a couple of times, and in these cases I generally turn the entire system off. I've noticed that upon returning and switching everything on again, the inverter behaves normally (i.e., allowing the usual 30+ A in) for about 5 days, then enters the above described suboptimal charge mode.

I have not been able to pinpoint how lengthy the switch-off should be for this sort of revival to happen. I know it does not happen overnight, but it does happen after the inverter has been off (everything disconnected) for about 24 h. I have validated this revival three times.

I am not posting the inverter parameters because they don't seem relevant --but I'll be glad to post any of them if needed. The inverter works fine --if only for a few days-- and this behavior did not occur initially, for a full year, despite the inverter having the same parameters it has now. The regulator's chip version is U2 04 12, and from the label it seems like the device was released in August 2017.

Any ideas what could be happening and why the thing "revives"? And is there any (safe) way to "cycle" the inverter so that I don't need to wait 24 h for it to resume normal charging?

IMG_20200523_201459_360.jpg

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9 hours ago, Álvaro said:

This is Álvaro, writing his first post from a sunny La Mancha, in Spain.

Welcome.

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and a so-called Huber 5 kW inverter/charger which I understand is some kind of Axpert clon (label below).

Actually, that looks like a genuine Axpert MKS to me. It might or might not be a 64 V model.

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In normal sunny days, the inverter used to allow in 30+ A from the panel array in the morning, with a half-empty battery. This seems consistent with the solar array capabilities.

Yes. Nearly 2 kW of panels, x 0.8 for heating and orientation, is about 1600 W, or about 32 A at 50 V.

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I am not sure when it started to happen, but now the inverter is not allowing this much power in anymore, and generally allows only up to some 13 A, even in clear sunny days. It does charge, and there are no failure warnings or anything: it just does not charge as much as it should.

 

I wonder if it's the premature float bug. Check the charge LED; if it goes solid before the battery is full, then the inverter is in the float stage prematurely.

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And here comes the funny thing. I have been away from home a couple of times, and in these cases I generally turn the entire system off. I've noticed that upon returning and switching everything on again, the inverter behaves normally (i.e., allowing the usual 30+ A in) for about 5 days, then enters the above described suboptimal charge mode.

That could be coincidental, but it's sounding more like there is something strange going on with your battery. Can you interrogate the battery about its state of health, or if it has error codes, or is balancing?

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The regulator's chip version is U2 04 12,

Yes, that's the Solar Charge Controller firmware version. As a point of interest, what's the main (U1) firmware version?

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from the label it seems like the device was released in August 2017.

Yes.

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Any ideas what could be happening and why the thing "revives"?

As above, that sounds like the battery needs to get to a lower state of charge, or just rest, to get into a state where it can take more charge. But I'd like to rule out premature charging first.

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Thanks, Coulomb. :)

33 minutes ago, Coulomb said:

I wonder if it's the premature float bug. Check the charge LED; if it goes solid before the battery is full, then the inverter is in the float stage prematurely.

I'll review this. I had also detected instances of the charge LED going solid after an evidently too short charging period. These cases were successfully resolved by cycling the inverter off and on again. Since they seemed to resolve with that simple operation, I had not given them much attention, but I'm positive it's happened.

However, in the suboptimal charge case I am describing, the LED blinks normally during charge.

The main firmware version is U1 74 10.

33 minutes ago, Coulomb said:

That could be coincidental, but it's sounding more like there is something strange going on with your battery. Can you interrogate the battery about its state of health, or if it has error codes, or is balancing?

I am afraid I cannot access the battery guts. It does have comm ports, but I don't have any software to enter and the maker seems somewhat hard to track down. From the looks and build, the piece is this one: https://www.alibaba.com/product-detail/5-kwh-lithium-ion-battery-lifepo4_60835731943.html?spm=a2700.details.deiletai6.3.7692SafPSafPCP.

The only significant situation the battery has been involved for these two years was a case of full unload. I had altered the original safety threshold of 48 V and during a cloudy month when I was absent, it got completely discharged.

33 minutes ago, Coulomb said:

As above, that sounds like the battery needs to get to a lower state of charge, or just rest, to get into a state where it can take more charge. But I'd like to rule out premature charging first.

I banned all resistance-based stuff from home, LOL, so now it's not that easy for me to discharge the battery. I'll start discharging it to the 48 V safety threshold as I do my research on the premature float bug.

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_ wonder if it's the premature float bug. Check the charge LED; if it goes solid before the battery is full, then the inverter is in the float stage prematurely.

Hi Coulomb,

Things went crazy with work and had to drop the testing. I will be completing the test procedure described in the reference post tomorrow.

Sorry if it's a silly question, but when the procedure says: Connect the utility., it may also be the solar panels, right? I don't have utility here. I could connect my generator, but if solar panels are okay in the test too, I'd rather use these.

By the way, the suboptimal charge I mentioned in my initial post does not occur on the generator. With the generator, I get to nearly 30 A of charge(which is the limit for utility charge I have in the setup anyway).

Right now (before the actual testing procedure from weber), I have [26] set at 55.0 V, [27] set at 54.0 V, and the battery voltage (during charge) is 54.6 V.
 

Álvaro

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On 2020/05/28 at 1:08 AM, Álvaro said:

the procedure says: Connect the utility., it may also be the solar panels, right? I don't have utility here. I could connect my generator, but if solar panels are okay in the test too, I'd rather use these.

Yes, that should be fine. You want a charge source so that the power won't go off. [ Edit: I mean, so that the inverter won't power itself down, just before the reflash starts. ] That recommendation possibly goes back to the days when the unit could be powered from AC-in.

Edited by Coulomb
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On 2020/05/28 at 12:28 PM, Coulomb said:

Yes, that should be fine. You want a charge source so that the power won't go off. That recommendation possibly goes back to the days when the unit could be powered from AC-in.

Thanks, Coulomb.

I ended up trying both with the generator and solar in two different days. Please see my worksheet below. I used option 2b because it seemed quicker considering my battery was not heavily discharged when I completed the test in the morning. Weber's test was positive --i.e., the inverter would go into an early flotation under these parameters.

I have to say that once I verified Weber's diagnosis, I turned all parameters back to my regular setup and the early flotation issue disappeared.

Do you think this glitch could have any relationship with this subcharging behavior? Note my problem is not that the inverter enters any early flotation mode. My problem is only that the inverter does not allow all the solar panels current in. Even if the battery would be in an early flotation (which is not the case except when it is, so to speak), I guess the inverter would allow all solar current in when connected to a significant resistance (e.g., the washdisher). This does not happen. The inverter does not allow more than 13-15 A from my 3+3 array of 325 W panels.

And just as a reminder of the oddest aspect of all this, the inverter does allow full charge (around 30 A) from the array during the first 5 days after a full system shutdown of at least 24 h. After these 5 days, the inverter does not allow more than 13-15 A in.1298967204_testprocedure001.thumb.jpg.2f761dd9b705f384803a80092a0716cb.jpg

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10 hours ago, Álvaro said:

Do you think this glitch could have any relationship with this subcharging behavior?

It could cause a similar problem, but no, see below:

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Note my problem is not that the inverter enters any early flotation mode.

Assuming that the above is correct, then no, I don't believe that the premature float bug is the cause of your particular problem.

10 hours ago, Álvaro said:

the inverter does allow full charge (around 30 A) from the array during the first 5 days after a full system shutdown of at least 24 h.

That is certainly weird. I can't think of any mechanism for that.

On 2020/05/24 at 5:11 PM, Álvaro said:

The main firmware version is U1 74 10.

Here's an outside possibility. Main firmware version 72.10 for the same model as yours except with the 64 V option is suspected to be buggy; it was quickly replaced by version 72.20. I have an unconfirmed suspicion that the 72.xx and 74.xx firmwares come from the same source code, just with different #defines active. So it's possible that 74.10 contains the same bug that 72.10 had. So updating to a later firmware version (e.g. patched firmware version 74.40e or even factory 74.40) may fix a bug, and that bug might be what is causing your problems.

Edited by Coulomb
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On 2020/06/03 at 3:32 AM, Coulomb said:

That is certainly weird. I can't think of any mechanism for that.

Here's an outside possibility. Main firmware version 72.10 for the same model as yours except with the 64 V option is suspected to be buggy; it was quickly replaced by version 72.20. I have an unconfirmed suspicion that the 72.xx and 74.xx firmwares come from the same source code, just with different #defines active. So it's possible that 74.10 contains the same bug that 72.10 had. So updating to a later firmware version (e.g. patched firmware version 74.40e or even factory 74.40) may fix a bug, and that bug might be what is causing your problems.

Thanks, Coulomb. It's so weird I am trembling a bit at the possibility that I might be missing some stupid thing. I am sending this to the guy who sold it to me. He'll do some testing on his end before sending it to the distributor, which might result in extra charges if they find I was indeed missing that stupid thing.

I'll sure let you know the outcome of all this.

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  • 4 weeks later...

Ok. I have a firm diagnosis: the user (that's me) is a stupid guy. :(

The culprit was a failing connector (in fact, two sequentially failing connectors) that effectively removed all current from one of the initially three, then two parallel series. I got misled by the sudden change in system behavior. All cables looked all right and instead of actually testing each I turned my eyes toward the inverter. My impression is that a small animal/bird used cables as an occasional swing, causing stress on the cable inside the connector and making it to slowly slip away --likely because it was improperly secured in the first place. 

Two lessons learned: a) all hardware needs to be tested, and b) all non factory-assembled connectors are main suspects in any performance drop situation, and cables are best secured to the panels frame.

I feel like I wasted a few people's time, including you, Coulomb. Sorry about that.

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16 hours ago, Álvaro said:

Ok. I have a firm diagnosis: the user (that's me) is a stupid guy. :(

The culprit was a failing connector (in fact, two sequentially failing connectors) that effectively removed all current from one of the initially three, then two parallel series. I got misled by the sudden change in system behavior. All cables looked all right and instead of actually testing each I turned my eyes toward the inverter. My impression is that a small animal/bird used cables as an occasional swing, causing stress on the cable inside the connector and making it to slowly slip away --likely because it was improperly secured in the first place. 

Two lessons learned: a) all hardware needs to be tested, and b) all non factory-assembled connectors are main suspects in any performance drop situation, and cables are best secured to the panels frame.

I feel like I wasted a few people's time, including you, Coulomb. Sorry about that.

Glad it's sorted. Well done.

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