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Axpert 5kVA Batteries do not last


Brad

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Hi

To give a bit of background, I have 6x260W panels connected 3 panels in series and the 2 banks of 3 in parallel. They are mounted on a solar tracker which gives around 1.2kW from 9AM to 5PM. I have 12 x 100Ah batteries 4 in series to give 48VDC and the 3 banks in parallel for a total of 300Ah @ 48V.

We constantly draw between 150W and 220W. The inverter cuts out at around midnight due to battery voltage too low. I think its set to 46V. 

My main concern is that when I look at the inverter the display says the batteries are fully charged at around 10AM and the battery voltage is 56 odd volts. 

With my limited knowledge and advise from my supplier, I have checked all settings and the supplier confirms the settings are OK. 

We have manually tested each battery and the batteries test 100% OK. They are only 6 months old. 

Can somebody please assist with which settings I should use. 

Thanks in advance

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Unfortunately, it could be chronic under-charging of the battery, due to the premature charge bug. Being declared full at 10 am at 1.2 kW sounds like they're not getting much charge.

Unfortunately, there is no patched firmware for the lower power models in your series. I had hoped that smaller models were immune to the charge bugs, but it seems that they may not be.

Unfortunately, your batteries may be damaged from this.

You need to see the battery voltage stay near the absorb / CV voltage while the current gradually drops to about a fifth of the maximum charge current (for a 300 Ah lead acid battery, this should be around 9 A). Important: if there is cloud or shade and the voltage isn't near the absorb / CV setting, then current dropping to 9 A (or whatever is the threshold for your system) doesn't count! If there is cloud or shade, when the sun returns, the charge voltage should go back to the absorb/CV voltage, and not stay at the float voltage (around 54.0 V, perhaps 55.2 V). If the battery goes to float voltage with the first cloud or shade, then you have the premature float bug.

What is your absorb / CV voltage? 56.0 V sounds low, depending on the type of battery. Please tell us the brand and model of battery. Increasing that voltage setting to the manufacturer recommended level could help a lot.

Quote

Sorry I made a mistake it's a 3kVA model SOL-I-AX-3Mplus48

When editing is allowed (it seems to come and go, at present it seems gone), I believe that you can edit the title of the thread/topic by editing the first message.

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Hi

Thanks for the speedy response. 

The system is installed on a mountain so I won't be able to check for the next week as I am on training at the moment. I will definitely go have a look as soon as I can. 

The absorb voltage as far as I remember is 56.4V. 

The strange thing is that when I first installed the system (over 3 years ago) it worked perfectly and would handle a bad weather stage of over 4 days without cutting out.  We then replaced all 12 batteries and now 6 months later it is giving us these problems. I'm sure almost sure it is not the bug. I have changed a few settings since and I'm not sure if they have anything to do with it. I installed the Icc software on a raspberry pi and the graph is attached. Please excuse the time though it stopped charging at 16:30 (this was before I installed the solar tracker). 

You can clearly see that during the time the panels were delivering sufficient power, the inverter was under the impression that the batteries were fully charged but then as soon as we lose solar power, it drops immediately. 

If the inverter has the bug, which inverter would you suggest I buy to replace? 

IMG-20180721-WA0020.thumb.jpeg.1860df13a477da91d1af56b48b938fa6.jpeg

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6 hours ago, Brad said:

We constantly draw between 150W and 220W. The inverter cuts out at around midnight due to battery voltage too low. I think its set to 46V. 
If the inverter has the bug, which inverter would you suggest I buy to replace? 

If that is the load, on a mountain, like off-grid, I would choose a small 800va or smaller Victron Phoenix inverter with a separate MPPT.

Would include a tablet and comms cables to get data uploaded and to be able to remotely login and check the system ... if there is a cell signal.

Edit: Then it is like plug and forget, for inverter works if there is batt power. And batts works if they are properly charged. Plug and forget.

Edited by Guest
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5 hours ago, Brad said:

... would much rather get my current installation working as I have enough expensive paper weights. 

Truth be told, I can sooo related to that statement.

At least you have an alternative now, one I can vouch for. Mine ran going 7 years 24/7/365 without a hitch.

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7 hours ago, Brad said:

The absorb voltage as far as I remember is 56.4V. 

That's the default for AGMs. The default for flooded lead acid is 58.4 V. You didn't say what sort of batteries you have.

7 hours ago, Brad said:

The strange thing is that when I first installed the system (over 3 years ago) it worked perfectly and would handle a bad weather stage of over 4 days without cutting out.  We then replaced all 12 batteries and now 6 months later it is giving us these problems.

Were the replacement batteries exactly the same brand and model?

It's also possible that you have at least one bad battery from new, and it's possible that it's dragged the others down or at least prevented the others from charging properly.

Quote

I installed the Icc software on a raspberry pi and the graph is attached.

The more important part is near the end of normal charging, say 8-10 am. But from the above, it looks like you're using the SOC as reported by the inverter, which is voltage based and not very accurate at all.

Quote

 

You can clearly see that during the time the panels were delivering sufficient power, the inverter was under the impression that the batteries were fully charged but then as soon as we lose solar power, it drops immediately. 

 

That's because the battery voltage drops immediately, with that very low load of 4 A (0.013C). Either the batteries are undercharged, or very low capacity.

Quote

If the inverter has the bug, which inverter would you suggest I buy to replace?

Sorry, I don't know the lower power models at all. I'd suggest a 5 kVA model, for which there is patched firmware available, but the standby consumption of these larger inverters (some 50 W) is about 25% of your load. So that would be quite inefficient for your application.

If it is the premature float bug, then it's so frustrating. What you have there is perfectly adequate for the job if just one word of flash storage was changed.

I do have a few firmwares that work with lower power models. What is the main firmware version for your inverter? I think ICC should be able to tell you.

- Mike

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Hi Coulomb, 

Thanks for the update. 

They are not exactly the same batteries but are lead acid. I suspect I have the battery type setting as AGM. 

I will check which setting it is on and update if required. I hope this won't damage the batteries. 

I will revert back. 

I just have to say that it is very comforting knowing that there are people out there so willing to help. A huge thanks to everyone. 

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8 hours ago, Coulomb said:

I'd suggest a 5 kVA model

For such a low load, I actually would not advise such a large model, as their no-load draw is quite significant (independent of manufacturer). I'm with TTT on that, I'd go with a 800VA phoenix, assuming of course that you never charge with another AC source, and that it accommodates your peak usage.

Of course that means an external MPPT, and of course I also understand that first prize is getting it working with what is there already :-)

I have no personal experience in this regard, but from what I have read on the topic, if you're going to run three parallel strings, you absolutely must charge the batteries properly, and by properly I mean you must overcharge them slightly to ensure that all the strings get a proper charge.

Edited by plonkster
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I realise that my statement came out very differently than intended. I should have said something like "I would have recommended a 5 kVA model, ..., except that ...". My reason is the same as yours, i.e. the overhead is ridiculous. 

Edit: Oh, and editing of other than the last post seems to have disappeared again. 

Edited by Coulomb
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@Brad if you are using ICC to control switching between grid and solar/batteries, then you have to set setting 12 ( Battery yo Utility) quite low. Mine is set to 44V on my Axpert 5kVA/4kW inverters. That is according to Jaco who originally posted AICC, the forerunner of ICC, on the forum. Otherwise the Axpert will interfere with the operation of the ICC. My setting 13 (Utility to battery) is set to 48V but I run on a time schedule. All that assumes you have a BMV700 or BMV702 feeding to ICC so as to get accurate SOC values. Without a BMV your batteries are most likely not being charged properly, given the Axpert's notoriously inaccurate sensing. A BMV will cost a whole lost less thatn a new set of batteries.

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Hi Coulomb, 

As per your previous post regarding Lead Acid and AGM. The inverter was indeed set to AGM and thus the low charging voltages. 

What should I set the Bulk Charging Voltage to and also what should I set the Floating Charging Voltage to? 

The Batteries are Royal 1150K batteries. 

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