Firmware release v2.1.09 and v2.0.09 for the Internal BMS batteries

On July 30th 2024 Lithionics engineering has released the updated firmware version v2.1.09 and v2.0.09 for batteries with Internal BMS.

Change Log Details:

• removed $MSOC command and remove $RVC=2 option, hardcode NeverDie reserve to cell voltage only, approximated to 10% SOC. Having RVC at different points depending on voltages or SOC is confusing to customers. When SOC is drifting it causes RVC to trip even when voltage is well above expected reserve level. This is causing numerous support calls and upset customers. According to mfg records no one has ever set MSOC above default 10%, and no one uses higher voltage RVC=2 option. It makes most sense to remove all these confusing options and set a single NeverDie reserve based on lowest cell reaching a true 10% SOC level. It also matches with a new algorithm to reset Usable AH and SOC at the same time, hence placing voltage and SOC based reserve in lockstep at actual 10% SOC.
• changed $LIST command output to include all values, including those only accessible in $SETUP mode. Some BMS parameters are protected from real time changes, those are usually specific to BMS hardware configuration and should not be messed with by customers. These values were only printed via $LIST command while BMS was placed in the $SETUP mode but were hidden if $LIST command was executed in runtime mode. However, this makes remote troubleshooting more difficult when we need to confirm all values, but don’t want to instruct customers to invoke the $SETUP mode. Now all values are printed in runtime mode, but changing protected values still requires placing BMS in $SETUP mode first.
• reduced re-bulk voltage from 3.35VPC to 3.33VPC to reduce repeated shallow re-charges. In systems which are charged overnight or have a long-term shore power connection we often see unnecessary re-bulk cycles due to quick settling of voltage. Reducing re-bulk voltage to 3.33VPC improves this issue by allowing longer settling time.
• increased warm battery charge rate reduction trigger from 50C to 55C based on customers real life testing data. When battery temperature is rising during charge, we can lower the max charge current to slow down the temperature rise and prevent BMS protection event due to battery overheating. The previous version did this at 50C, giving 10C remaining rise at a lower rate. Analysis of real-life customers data logs has shown that the 10C gap is too large and unnecessary as the temp rise slows down quickly when the charge rate is capped. A gap of 5C is plentiful, so the threshold was raised to 55C.
• improved Abs -> Float transition to reduce target current until highest cell drops below float. When target charge voltage drops to float level at the end of charge cycle it is necessary to prevent continuous charge current, because most chargers don’t react quickly enough to reduced voltage target and continue to push current, hence causing voltage overshoot and possible HVC events. Now we are setting target current to zero, to which chargers reacts quickly, when entering float stage, until battery voltage naturally falls to float voltage level, at which point we return to max charge current, but at the float voltage level, as desired.
• changed remaining discharge time calculation to zero out at 10% SOC instead of 0% SOC, to match with NeverDie Reserve cutoff. Customers complained that the remaining discharge time was above zero when BMS triggered NeverDie Reserve, which is confusing as we want customers to start charging before they reach the reserve. Now the remaining discharge time is scaled to reach zero when SOC is 10%.
• adjusted cell voltage level for RESERVE to better match with 10% SOC measured in recent lab tests. Previous cell voltage level of 3.00VPC did not correspond to expected SOC values of 10%. As part of Usable AH algorithm implementation, it was determined that correct value is 3.14VPC. This is an Open Circuit Voltages (OCV), under load it is offset in real time by 0.01VPC per 0.1C load rate.
• added usable AH calibration function to improve SOC accuracy. Battery usable capacity slowly fades over time as battery is aging, which decreases SOC measurement accuracy. Occasionally battery capacity needs to be calibrated to improve SOC measurement accuracy. This is now done automatically when the battery is continuously discharged from 100% to 10% SOC within a 12-hr. period.
• added corrections for large >15% SOC discrepancy compared to known cell voltages during discharge. If BMS was powered off for a long-time during storage, it’s remembered SOC could be significantly higher than actual SOC of the module(s) subject to self-discharge while in storage. It is necessary to bring SOC closer to reality until a proper full charge cycle can be done to re-sync the SOC at 100%. According to lab discharge logs we selected several SOC points with discernable corresponding cell voltages, at 70%, 40%, 20%, 10%, 5%. If BMS “remembered” SOC is more than 15% above these points when cell voltages correspond to those points, the SOC is adjusted in real time to those points, to remove large discrepancy, until a proper SOC re-sync can be done by a full charge cycle.
• improved CAN source address filter to prevent rare conflicts with 3rd party devices. Resolves rare CAN issues in complex systems.