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Axpert King + Pylontech - questions & firmware whishlist


Obinoux

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Hi !

I recently started to install multiple offgrid setup in south of France based on pylontech US2000 & US3000  and Axpert King 5KVA , each with 4x450W solar panels (wiring of pannels are two strings of two serialized panels (OC voltage is ~100V) , these two strings are in parallel on the unique MPTT of the inverter)

Firmware version are 70.73 for main DSP and 2.60 for display.

Its quite efficient in summer and mid-season, but I'm having a few usability issues with the current, cloudy weather extending on multiple days :

1) It looks like the King does not have the "Power Saving" function that other models have, the function which automatically cutoff the 250V output whenever no load is present - which saves about 20-40Wh of the inverter self-consumption.
Am I right ?
If yes I'm thinking about a system (like raspberrypi or arduino-based) to do that "externally" , which would be in parallel on the inverter button.

2) I setup the "pyl" on the configuration value number 5 . However I'm quite dismay by the values I see in the registers 2,26,27,29:
* 02 stays at 10 Amps (see below)
* 26 (bulk charge) looks quite low to me at 52.4V
* 27 (floating) looks also quite low at 52V
* 29 (low DC cutoff) looks quite high at 51V (!) .
The battery doc talks about max charging voltage 53.5 and min voltage of 45V (15-cells).
Of course I know these is a security margin to apply . The issue here is I cannot change these values unless I switch to "User Mode" in register 5, which do not uses the communication link with the battery.  Do you know if there is a way to change and store these values permanently event in "Pyl" mode ?

3) The 02 registers is documented as the max charging current , and stays at 10A unless I use the User Mode in register 5.
My US3000 can takes safely 37A, and my US2000 (another setup) can takes 25A.
It looks likes this value is not taken into account for solar charging (I could get much more than 10A in a few occasion.

However, my problem is that it *is* taken into account for grid recharge , which in my case happen to be a fuel generator
10A@48V is 480W , and I could pull much more from the generator , shortening the running time for the generator.
I did pull 30A at one time, *if* I disable the "Pyl" mode and switch to "user" mode. But again, I'm not willing to do that on the long run.

Again, do you know if a later firmware changes this or allow this setting to stick ?

4) My generator is a small one. When I set 30A (with the procedure above) , the inverter switch from 0 to 30A instantly. This makes my generator slow down and get under 46Hz, which disable the AC input on the inverter. At this moment the generator takes back its RPM, returns at 52Hz, which re-enable the inverter, which enable  the 30A , which .... well , you see the problem.
Of course I know the trick which consists in putting a load on the generator first before plugging in the inverter, but it is a fragile procedure and does not always succeed.
I however succeeded to pull 30 amps by switching from 10A to 20A, and then from 20 to 30A in the "02" register while running (and, of course, in "User mode" for the 05 register).
Not a very practical.
I'm not sure it's possible to do that in the current firmware but maybe in a later one ? This looks to me like something that can be done in software (not sure if the 10 amps "step" may be decreased)

 

On overall, I don't know what to think about this inverter : Electronic looks good and reliable, although the self-consumption my be a bit high (especially if there is no power-saving mode).
But  for be it's lower than average on the software side - which would greatly benefit from source disclosure and more control on the parameters values.

Thanks for reading !

Obinoux

 

 

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On 2021/11/21 at 12:25 AM, Obinoux said:

Firmware version are 70.73 for main DSP and 2.60 for display.

I've not heard of 70.73 main firmware. Is this a typo? Is it possible the machine is a clone?

02.60 is fairly old for the removable display. I would update it to 02.66.

Quote

 

1) It looks like the King does not have the "Power Saving" function that other models have, the function which automatically cutoff the 250V output whenever no load is present - which saves about 20-40Wh of the inverter self-consumption.
Am I right ?

 

Cutting off a small load will only save consumption equivalent to that load plus a little for losses. I think you want to turn the inverter off, not turn off the load. That can't be done externally, unless you somehow control the on/off switch, or use advanced patched firmware, which isn't available yet.

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If yes I'm thinking about a system (like raspberrypi or arduino-based) to do that "externally" , which would be in parallel on the inverter button.

Ah. OK, that could work, with a ≈30 second delay between turning off the inverter switch and the inverter actually switching off.

Quote

 

2) I setup the "pyl" on the configuration value number 5 . However I'm quite dismay by the values I see in the registers 2,26,27,29:
* 02 stays at 10 Amps (see below)

 

That seems odd. I would expect it to go to 30 A unless the battery is nearly full. 

Quote

* 26 (bulk charge) looks quite low to me at 52.4V
* 27 (floating) looks also quite low at 52V

Those values look sensible to me. Which means I don't expect those values from a Pylontech BMS. That sounds a bit mean, but that's my very limited experience so far.

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* 29 (low DC cutoff) looks quite high at 51V (!) .

I will agree that that's crazy high. It's 3.4 VPC, well over 80% SOC, unless it's charging very hard. Maybe they are doing charge current compensation? But with a charge current limit if 10 A, that can't be the case.
 

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The battery doc talks about max charging voltage 53.5 and min voltage of 45V (15-cells).
Of course I know these is a security margin to apply .

 

The Pylontechs don't seem to apply any margin. Or at  least they didn't.

Quote

The issue here is I cannot change these values unless I switch to "User Mode" in register 5, which do not uses the communication link with the battery.  Do you know if there is a way to change and store these values permanently event in "Pyl" mode ?

No, the whole point of the BMS cable is that the BMS takes control. I've dreamed about applying some limits to what the BMS commands (making it more of a suggestion than a command), but I've not implemented anything.

Quote

Again, do you know if a later firmware changes this or allow this setting to stick ?

You can't get it to stick, and I don't know of any firmware that puts limits on what the BMS commands.

I'm wondering if your battery needs a firmware update or something. This should all be driven from the BMS.

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4) My generator is a small one. When I set 30A (with the procedure above) , the inverter switch from 0 to 30A instantly.

I have little experience with the BMS to inverter cable, but I always found the charge current would ramp up slowly. Obviously, it's different with the BMS cable.

Quote

 

I however succeeded to pull 30 amps by switching from 10A to 20A, and then from 20 to 30A in the "02" register while running (and, of course, in "User mode" for the 05 register).
Not a very practical.

 

It looks like you might need a small computer between the BMS and the inverter, to implement the 10A stepping automatically. Or patched firmware to implement this, but it will take some time and I can't promise anything. Waiting and hoping for Voltronic to improve the firmware doesn't seem practical.

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(not sure if the 10 amps "step" may be decreased)

Depends on how it's done. The 10 A steps are pretty well embedded in the removable display firmware, but gentle ramps for any utility charge current changes might be doable in the DSP firmware.

 

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