State of Charge Calculator for Battery Cell Balancing
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Solution Overview
Problem
Existing energy storage systems with cell balancing technologies face challenges in accurately monitoring the state of charge (SOC) due to dissipative devices diverting current, making it difficult to track SOC accurately.
Innovation Solution
The solution involves using dissipative devices with known resistance values to sense and correct the current measurements by calculating the error introduced by these devices, allowing for a more accurate determination of SOC through Ohm's Law and subsequent circuitry processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If dissipative devices are added for cell balancing, then cell voltage uniformity is improved, but SOC measurement precision deteriorates
Solution Approach 1:
The patent segments the current measurement by separating the total current from individual cell currents. Current sensors are placed on each cell to measure individual currents, and these measurements are combined to calculate the net current for SOC determination, effectively isolating the dissipative current effect.
Solution Approach 2:
The system implements feedback by continuously monitoring individual cell currents and using this information to correct the SOC calculation. The controller receives current measurements from each cell, calculates the dissipative current, and adjusts the SOC determination accordingly, creating a closed-loop measurement system.
2Stability of the object's composition
If dissipative devices are used for cell balancing, then cell voltage stability is improved, but current measurement accuracy deteriorates
Solution Approach 1:
The patent extracts the dissipative current component from the total current measurement by measuring individual cell currents separately. This allows the system to isolate and remove the dissipative current effect from the SOC calculation, achieving accurate current measurement despite the presence of dissipative devices.
Solution Approach 2:
Individual current sensors act as intermediaries between the dissipative devices and the SOC calculation system. These sensors measure the current through each cell including the dissipative current, providing data that enables the controller to calculate and remove the dissipative component.
3Reliability
If cell balancing with dissipative devices is implemented, then battery system reliability is improved, but SOC tracking accuracy deteriorates
Solution Approach 1:
The system segments the battery into individual cells with separate current measurements, allowing the SOC to be tracked for each cell independently. This segmentation enables accurate SOC determination despite the presence of dissipative devices used for system reliability.
Solution Approach 2:
The controller implements feedback by continuously monitoring individual cell currents and adjusting the SOC calculation in real-time. This feedback mechanism ensures accurate SOC tracking while the dissipative devices maintain system reliability through cell balancing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables more precise SOC monitoring by correcting the cumulative current and charge values, providing a net, accurate SOC measurement that was not possible with prior systems.
Implementation Method 1
dissipative devices with known resistance values to sense and correct the current measurements
Implementation Method 2
calculating the error introduced by these devices, allowing for a more accurate determination of SOC through Ohm's Law
Data Source
AI summary
An arrangement for monitoring the current or state of charge (SOC) of an energy system (230) having one or more series-connected strings (S1, S2, . . . Sn) of battery cells (C1, C2, . . . Cn). The battery cells each have respective dissipative devices (D1, D2, . . . Dn) selectively connectable in parallel therewith for balancing cell voltages in the string. The dissipative devices are of predetermined, typically equal, impedance value. The voltage across each cell (Vc1, Vc2, . . . Vcn) may be separately monitored, such that by dividing the monitored voltage across a cell by the impedance value of a dissipative device connected in parallel therewith, the dissipative current is determined. A summation of all of the dissipative currents yields an error value, which error value is then removed from the measured gross current (Ibat) flowing through the combined battery cells and dissipative devices to yield a corrected value of current (Ibatnet). A corrected SOC value (Qnet) is obtainable in a similar manner.