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Axpert king with Lithium Iron Phosphate battery


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I have been following this forum for some time and still have a question that has probably been extensively dealt with but I cannot find such a complete discussion. So please bear with me. 

I run  an Axpert king 3kW inverter (removable console) with solar panels giving 1.3 kW and  a 24V 6.3 kWh LiFePo4 battery composed of an 8 serial 2 parallel arrangement of cells, supervised by a Daly bms. The Axpert main CPU version is 51.08, secondary CPU is v02. 00, SCC version 1.10. Our overnight household power usage is about 1.8 kWh. 

My problem is that the inverter is not set up for lithium batteries (unless pylontech) and the shallow charge curve. My approach to running the system is to charge up to 75% SOC and discharge to 25%. To achieve this I bulk charge to 27.3V and then float at 27.1V. My problem is that the Axpert charges at a slow rate (around 500W). On sunny days it eventually gives the full charge, but on cloudy days the low charge rate is problematic. However, if I set the bulk charge voltage to 27.6V then the charge rate increases to over 1kW which is what I would have expected in the first place. Our washing machine draws 2.2kW (only for 2 minutes) and when using that, the solar panels deliver close to their maximum capacity. So I am convinced there is not a panel efficiency problem. 

Now, I gather there has been a number of updates to the firmware of the Axpert King, done by Coulomb and some Australians. I need to understand whether a firmware reflash will solve my problem. I cannot find a systematic description of what issues were addressed in these firmware changes and whether they could alleviate my problem. 

I regularly download logs from the Axpert to a memory stick using a USB OTG cable. I have managed to decode most of the information in the log files. 

Apologies for such noob questions, but I suppose one needs to start somewhere. Any information about useful links for addressing the above issue will be very much appreciated. 

Kind regards, willemf

 

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6 hours ago, WillemF said:

The Axpert main CPU version is 51.08

Ah. I've never seen that one, or any 51.XX version. Kings are different to VM IIIs, in that they have different firmware for 5 kW and 3 kW models.

6 hours ago, WillemF said:

secondary CPU is v02. 00

That's getting a bit old, but the later versions are mostly to do with BMS communications, which you aren't using.

6 hours ago, WillemF said:

Now, I gather there has been a number of updates to the firmware of the Axpert King, done by Coulomb and some Australians.

Yes, but it's for 5 kW firmware only. We're still working on it, but at least the two premature float bugs, and LFP thresholds have been fixed. But sadly, that doesn't help you.

6 hours ago, WillemF said:

I need to understand whether a firmware reflash will solve my problem.

I doubt it, and there are none available on the web that I know of. You might be able to get more recent firmware from your supplier, but I somehow doubt that it would fix your problem.

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