Rello

Solution: Resetting the Battery Management System (BMS) to Address Rapid Discharge
The rapid drop from 69% to 0% state of charge (SOC) on your CFE 5.12kWh lithium batteries suggests a potential issue with the Battery Management System (BMS) misreporting the SOC. This can happen if the BMS has drifted or lost calibration, causing the inverter to misinterpret the battery’s true capacity. Resetting the BMS by recalibrating the full and empty states in voltage mode (or lead-acid mode) may resolve this issue. Below is a step-by-step guide to safely reset the BMS for your Luxpower inverters and CFE batteries.
Preliminary Checks
Confirm BMS Communication:
Verify if your Luxpower inverters are set to communicate with the CFE batteries via BMS (using CAN or RS485) or if they are in voltage mode.
Check the inverter’s LCD or app for the battery type (setting 3). It should be set to “Lithium” with battery code 6 (for CFE). If it’s in voltage mode, the BMS is bypassed, and the issue may be related to incorrect voltage settings.
Gather Battery Specifications:
Refer to the CFE 5.12kWh battery manual for the following:
Full Charge Voltage: Typically 56.4V–57.6V for a 51.2V nominal lithium battery.
Empty Voltage (Cutoff): Typically 48V–49V to prevent over-discharge.
If you don’t have the manual, contact your CFE supplier or assume conservative values (e.g., full charge at 56.5V, cutoff at 48V).
Safety Warning:
Do not discharge the battery below its specified minimum voltage (e.g., 48V) to avoid triggering the BMS’s over-discharge protection, which could damage the battery or require professional intervention.
Work with a qualified technician if you’re unsure about any step, as incorrect settings can harm the battery or inverter.
Step-by-Step BMS Reset Procedure
This process involves switching the inverter to voltage mode (or lead-acid mode), disconnecting BMS communication, and cycling each battery individually to recalibrate the BMS. Perform the steps carefully to avoid over-discharging or overcharging.
Preparation
Switch to Voltage/Lead-Acid Mode:
On the Luxpower inverter’s LCD or app, go to setting 3 (Battery Type).
Change from “Lithium” to “Lead Acid” or “Voltage Mode” (depending on your firmware’s terminology).
Set the following voltages based on CFE battery specifications:
Charge Voltage: Set to 0.1–0.2V above the full charge voltage (e.g., 56.6–56.7V if the spec is 56.5V). This ensures the BMS recognizes a full charge without overcharging.
Discharge Cutoff Voltage: Set to the minimum safe voltage (e.g., 48V). Do not set it lower to avoid over-discharge.
Save the settings.
Disable BMS Communication:
Unplug the CAN or RS485 communication cable between the inverter and the battery. This forces the inverter to rely on voltage readings instead of BMS data.
If you’re unsure which cable is the communication line, consult the Luxpower or CFE manual or contact your installer.
Isolate Batteries:
Since you have two CFE batteries, work on one battery at a time to ensure proper recalibration.
Turn off or disconnect the slave battery (check the CFE manual for master/slave configuration). Ensure only the master battery is connected to the inverter.
Resetting the First Battery
Discharge the Battery:
Operate the system normally to discharge the master battery until it reaches the cutoff voltage (e.g., 48V) or the inverter alarms for low battery.
Critical: Monitor the battery voltage closely via the inverter’s LCD or a multimeter. Stop discharging immediately if the voltage approaches the minimum specified value to prevent over-discharge.
If the inverter cuts off early (e.g., at 69% SOC), the BMS may still be intervening. Double-check that the communication cable is disconnected and the inverter is in voltage/lead-acid mode.
Recharge the Battery:
Allow the inverter to charge the battery from the grid (or solar, if available) until it reaches the set charge voltage (e.g., 56.6–56.7V).
The slight overvoltage (0.1–0.2V above spec) should trigger the BMS to recognize the battery as fully charged, recalibrating the 100% SOC point.
Caution: Do not exceed 0.3V above the specified full charge voltage to avoid overcharging, which could stress the battery or trigger BMS protection.
Verify Calibration:
Once fully charged, check the inverter’s SOC reading (if available) or measure the voltage to confirm it aligns with the battery’s full charge specification.
Reconnect the BMS communication cable and switch the inverter back to “Lithium” mode (battery code 6 for CFE).
Resetting the Second Battery
Switch Batteries:
Turn off or disconnect the first (master) battery.
Connect the second (slave) battery to the inverter, ensuring it’s the only battery active.
Repeat steps 4–6 for the second battery, discharging to the cutoff voltage and recharging to the full voltage.
Final Setup
Reconnect Both Batteries:
Reconnect both batteries (master and slave) as per the CFE manual’s configuration.
Ensure the BMS communication cable is reconnected.
Set the inverter back to “Lithium” mode with battery code 6.
Test the System:
Monitor the system over a few days to confirm the rapid discharge from 69% to 0% no longer occurs.
Check that the SOC readings align with expected battery behavior during discharge and charge cycles.
If the Issue Persists
Possible Battery Fault: If recalibration doesn’t resolve the issue, one or both batteries may have cell imbalances or degradation. Contact your CFE supplier to check warranty status (typically 10 years) and request a professional inspection of cell voltages and BMS logs.
Cell Imbalance Cause: If the batteries are kept at 100% SOC for extended periods without cycling, cell imbalances can develop. To prevent this, cycle the batteries (discharge to 20–30% SOC) once or twice a month, especially during high solar production periods.
Inverter Settings: Double-check other inverter settings, such as maximum discharge SOC (setting 11, set to 20–30%) and time-based charge/discharge schedules (settings 13 and 14). Ensure they allow grid charging during early morning and evening to avoid unnecessary battery cycling.
Firmware Update: Contact Luxpower support ([email protected]) to verify your inverter’s firmware version. Older firmware may cause BMS communication issues.
Additional Recommendations
Use Monitoring Tools: If possible, install a monitoring tool like Solar Assistant to track real-time SOC, voltage, and current for better diagnostics.
Join Community Groups: Connect with other Luxpower users via the LuxpowerSA Facebook group or WhatsApp community for shared experiences and solutions.
Professional Assistance: If you’re uncomfortable performing these steps or lack access to the inverter’s app, consult your installer or a qualified solar technician.
Safety Notes
Always follow the CFE battery and Luxpower inverter manuals for specific voltage settings and procedures.
Avoid discharging below the minimum specified voltage or charging above the recommended voltage to prevent damage.
If you notice unusual battery behavior (e.g., overheating, swelling, or BMS errors), stop the process and contact the supplier immediately.

I'll add that roughly matching your inverter's voltage with the typical utility voltage means that the changeover relays have an easier life and with load shedding, they will work hard.
I increased my output voltage from 230V to 240V for that reason. 

Agree - I'm also one of them with 2x5kW inverter. And what I wrote concerning the kettle also applies to the geyser. However I pay attention not to run the geyser during LS at night. At the end of the day it all boils down to how much energy you have stored in your battery. Therefor the more battery capacity the better.

On average I agree with you. But we just have to look around how many people install 2x8kW inverters and that indicates they want to run all their loads as normal during LS. Also look how many want to run their geysers from the inverter=always on. 
Over the last few days there was a question on how to run the geyser on essentials instead of non essentials. 

My post was about AC. Your examples are for DC circuits. 
I cannot educate but the impedance is the important factor for AC circuits. Z=root of Rsq+Induct sq. So the impedance Z remains the same in the circuit. Lower volts means lower current. All circuits are made up of inductance/capacitance as well as resistance. 
Thus if you lower the voltage there is already a reduced current due to the lower voltage with the same impedance that cannot be changed by the voltage you apply. 
I can't explain well and for that reason I supplied the actual measurements with the variable being the voltage. 
Power for a AC circuit was never P=VxI as the PF can be as low as 0.5 which will reduce the power to 50% at the same volts and current. 
It is for this reason that we find inverter specs at times showing VA as well as Watts and the values differ. 
We as small consumers are charged only for the active power Watts we use. Big consumers are charged for the VA used which is always higher and the VA dictates what amps will have to be provided or transmitted. The best example that I can think of is when you buy a transformer. It is never specced in Watts but VA. 
 

Motor loads vary and that I understand.
However when you have a device that draws a constant load, i.e. a globe and you reduce the voltage, then the Amps increase.
A good example are computer chips and specifically CPUs. Over the years the voltages for electronic components have been reduced where a typical CPU nowadays runs at 1,5V or less. The frightening part is when you see how the Amps have since shot up where a 100Amps has become quite normal just for the CPU or GPU for that matter.
So as the load increases so do the Amps.
If the formula of P= V X I is not valid anymore for constant currents then I may be living in the past and would like to be educated.
 

I think we need to explore the half truth from social media/forums about the fact that motor loads always draw more current when you reduce voltage. 
I will try to explain this statement. 
If a 220W motor load is connected to 220V (for ease we ignore PF) we draw 1A.
Most household motor loads we will find only needs below 180W. In this case the current will not be higher than 1A.
If the above example needed the full 220W for the load(output power) then the current could go up to around 1.1A if the voltage drops to 200V.
Below is an example of the same load being a fridge with 110W motor but only needs around 70W for the output load. 
Reduced power used even when the voltage is only 2 volt lower and current remained the same. 

The inverter is already set at 230V as can be seen when there is LS. Other times the grid voltage goes to loads as the inverter is on bypass. The inverter adds no contribution to steady voltage when the grid is on. 
My feeling is one can get about 3.5% longer run time when there is LS by reducing the voltage to 215V. Not worth it to reduce due to negatives already indicated. 
Having a too narrow grid healthy setting could mean more battery power will be used when the grid is on. 

Your supply Voltage is already on the lower of the scale end most of the time, and after loadshedding it drops out of range. You could rather consider setting the Voltage limits on the inverter to the standard 230V +/-10% to help protect your appliances so they don't draw excessive current.
 

The difference will by minimal depending on the base load, but using a lower voltage means your Amps increase and your battery has X amount of Amp hours.
Lets assume your base load overnight is 500W.  If you are at 230V, then 500/230 = 2,17A.  If you are at 210V, then 500/210 = 2,38A
You can see with the lower voltage your Ah will increase not decrease, so it will have the opposite effect of what you wish to achieve.

@Rello The SOC is an estimate and is based on an algorithm. It is not accurate. You will notice your SOC spikes every time your battery power spikes. This happens on a lot of batteries and is not a serious issue. Many factors influence SOC such as temperature, accuracy of measurement, the algorithm used, age of batteries, battery chemistry, battery internal resistance, etc. One top tip I can give you is to charge your batteries to 100% at least once a day to help the SOC algorithm work correctly.

Yes, but just make sure to tick the box for "Grid Charge" under the battery menu, if you want to charge via grid.

Yes it will. Batteries will discharge during LS then top up outside of LS

Good day all,
I have my Deye inverter running since November last year and very happy with it. I'm quite used to using the TIME OF USE screen to get optimum use during Load-shedding/Cloudy days.
I will be going away for a week or so and will have house sitters looking after everything. I can't expect them to fiddle around with these settings, so what I'd like to know is if I Un-tick TIME OF USE, will the system work purely like a UPS, providing power when load-shedding occurs and recharge via Grid or PV when available?
Thanks everyone! 🙂
 

You are running Dyness batteries which are 80% DOD (you can run then down to 20% and not impact / affect warranty etc) so a discharge from 100-25% is within the manufacturer bounds. What's key though is understanding your home usage patterns. If you set your minimum to 25%, if the batteries reach 25% at 2 / 3am - is that enough to take you to 7 / 8 am for PV to take over? You also have 6000 cycles at an 80% DOD so at 1 cycle per day that's approx 15years before you should run into any capacity issues
What i have done is a stepped approach - so i allow mine to run down to:
75% before 9:45pm 65% before 11:45 20% before 5am - so if LS hits at 5am i have enough in the tank until 7am when PV is greater than load. This is based on knowing that if i have 65% at midnight i can make it to the morning