Feature Request: Lithium charging setting for LuxpowerTek SNA

[shvm]

What equipment I have:​

Luxpower SNA 5k paired with JK-BD6A24S10P BMS monitoring a 16 Cell 100Ah CALB LFP battery
BMS comms is not currently possible

The issue I'm currently facing:​

I have to put time and efforts changing charging parameters everyday for correctly charging the battery.
Very specifically, Everyday I have to bring the value of "Charge Voltage for Lead-Acid Battery" (ConChrg) from 56.1 to 53.6 (float) after charging current starts tapering at full charge. Then I have to change this value back to 56.1 V again the next day before daybreak.
Solar power gets wasted on days I forget due to slower charging speeds at 53.6 V.

What I want:​

A simple LFP specific charging parameter setting that terminates charge when charging current starts tapering.
New charging cycle is initiated again when Cells dip below a threshold voltage.

LXP SNA can already measure the amount of current going into battery specifically as demonstrated by this screenshot.
It should be trivial to implement what I have outlined using minimal lines of code.


As one can clearly see, Out of 1290 W produced by PV, 111 Watts (2 Amps) is being used to charge the battery and the rest used to supply loads.

---

Implementation details:​

According to datasheet for my CALB L160F100 Cells,




A dead simple linear approximation for determining tapering current according to targeted charge voltage would be:



Termination Current (in Amps) = Termination Current in Amps × (Calibrated Charging voltage per Cell - 3.375) / (3.625 - 3.375)

Simpler termination formula (for newer LFPs),
Termination Current (in C) = 0.2 × (Calibrated Charging voltage per Cell - 3.375)

The inverter can ask for four configurable settings (first two are defaults):

1. Threshold voltage for starting new charge cycle, a good default is 3.35 V/Cell
2. LFP Full Charge Voltage (Optional, used for tapering current calculation at lower charging voltages), default at 3.375V/Cell
3. Calibrated Bulk Charge Voltage (must be manually verified by a multimeter or set at a safe lower value), <3.65 V/Cell. I use 3.55 V
4. Current termination Criteria according to Cell manufacturer datasheet, usually 0.05 C but can be 0.033 C also for old chemistries.

Expected behaviour:​

Once the battery voltage rises to 3.55 V/Cell and the charging current has dipped below 0.03 C, charging should be stopped.
Once the battery voltage has come down to 3.35 V/Cell, charging can be attempted again.

On overcast/cloudy days, it is possible for the battery voltage to never reach CV phase of the charging.
That is the reason behind termination current determination using formula provided above.
For instance, if the available charging current is 0.03 C only at max, then as soon as battery voltage increases beyond 3.525 V/Cell, charging must be terminated.

Reference: https://nordkyndesign.com/charging-marine-lithium-battery-banks/

Please tag Luxpower Representatives in this forum. This should have been a feature years ago.

 

[shvm]

@Luxpower_Gilbert
Are you able to do the needful regarding this feature request?

I have a 100Ah LFP battery and I want the LXP 5k to terminate charge based on the current going into the battery.
I have to keep changing settings everyday manually in its absence.

 

[Luxpower_Gilbert]

@Luxpower_Gilbert
Are you able to do the needful regarding this feature request?

I have a 100Ah LFP battery and I want the LXP 5k to terminate charge based on the current going into the battery.
I have to keep changing settings everyday manually in its absence.

It can only done with battery SOC ( closed loop communication) or voltage.
Your request can be done with HomeAssistant Automation…

 

[shvm]

It can only done with battery SOC ( closed loop communication) or voltage.

The inverter can already measure charge power (red) specifically going to the battery beside load (blue). That means current is known. Power = V × I
Check screenshot.



What I'm asking for is this:
If at a charging voltage, say 56V, the inverter measures battery charge power go below 56 V × 5 Amps, it switches to float.
It's this simple really.
I don't understand why it requires closed loop communication because the inverter knows current going into battery.

Edit 1: I think the inverter has started doing this automatically. I observed it switching to float automatically today when current dropped to 5 Amps.
But I don't spot any option in settings.
What is going on ??

Edit 2: The inverter began another charge cycle but this time didn't switched to float after 56 V. What is this !!?

I will post a screen recording tomorrow showing this in action because this would appear unbelievable.