Battery knowledge · Modules, packs and battery management
Voltage sensing
Measuring each series cell group’s voltage through a wire or flexible circuit from its busbar to the monitoring chip. Millivolt accuracy matters because the BMS reads SOC and detects faults from these numbers. [1]
- Also called
- cell tap, sense line
- Unit
- mV
Example
The limiting cell matters
Average: 3.93 V. Highest cell: 4.02 V. The highest cell can reach the charge limit first.
The 4.2 V ceiling is an example, not universal. Voltage alone does not uniquely determine SOC.
Explore the graph
A pack average can hide a cell that reaches its voltage limit first.
Average: 3.93 V. Highest cell: 4.02 V. The highest cell can reach the charge limit first.
V_max = max(V₁, V₂, …); V_average = ΣV_i / N
Illustrative model. The 4.2 V ceiling is an example, not universal. Voltage alone does not uniquely determine SOC.
Use in Lemonergy
Lemonergy Studio blocks
Relate current and voltage
Conserving components solve constitutive relations and node balance.
Blocks to use
- Controlled voltage source
Supplies voltage
Inputs & settings
- voltageV
- Resistor
Relates current and voltage
Inputs & settings
- resistanceOhm
- Electrical reference
Sets zero potential
Inputs & settings
- Connect p to reference net
This overview identifies the components to use. Follow the example in Lemonergy for their connections and settings.
Example. A 1 V drop across 2 Ω implies 0.5 A.
Observe. Topology sets individual element voltages.
The RC example includes a capacitor: transient current varies and source voltage is not always resistor voltage.
Open the electrical circuit →References & further reading
Technical references
- Getting Started with the BQ76925
Texas Instruments · 2019
Technical reference · A concrete BMS analog front-end example: cell voltage, current, temperature measurement and MCU integration.
Further reading on this topic
These sources provide broader context; they are not presented as citations for every statement in this entry.
- Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs: Part 2. Modeling and identification
Gregory L. Plett · Journal of Power Sources · 2004
Topic background · Battery charge balance, open-circuit voltage, ohmic loss, polarization dynamics and model identification; parameters require cell-specific data.