Configuring a JK BMS for Non-LFP Chemistries: Sodium-Ion, LTO, and NMC

The JK BMS (Jikong) family has become the community default for 16S LFP builds, but the hardware supports other chemistries through configurable voltage and protection parameters accessible via the JK BMS mobile app or RS485 interface. The default firmware ships with LFP-specific voltage ranges that will cause problems with sodium-ion or LTO cells if left unconfigured: a BMS set for LFP's 2.5V–3.65V per-cell range will interpret a full LTO cell (nominal 2.4V, max 2.8V) as critically overdischarged and disconnect the pack. Getting non-LFP chemistries working correctly requires setting the right parameters before first connection to the pack.

The chemistry-specific settings that matter most: LTO cells operate between 1.5V and 2.8V with a 2.4V nominal — set the JK BMS low-voltage protection to 1.8V and high-voltage cutoff to 2.85V. Sodium-ion cells (hard carbon anode, layered oxide cathode) operate between approximately 2.0V and 4.0V with a 3.0V nominal — set low-voltage protection to 2.2V and high-voltage cutoff to 4.05V. Balancing activation voltage and SoC estimation also require chemistry-specific adjustment; SoC estimation is the trickiest parameter because sodium-ion's voltage curve is steeper than LFP's characteristically flat discharge, meaning the default SoC calculation will report inaccurate state of charge until the curve is recalibrated. Community-documented parameter sets for each chemistry are available in the forum's BMS configuration thread.

Open-source tools for monitoring JK BMS units exist and are worth knowing about separately from configuration. The jkbms Python library (available on GitHub) reads real-time cell voltages, temperatures, current, SoC, and cycle count via Bluetooth and integrates with Home Assistant and MQTT for long-term monitoring. These are read-only tools — they don't modify BMS configuration — but they enable per-cell degradation tracking that the official app doesn't preserve over time. For non-LFP builds where cell aging curves are less well-characterized than LFP, pairing a JK BMS with external monitoring is a worthwhile addition to any build.