Mixed-Chemistry Battery Module Balancing With SOC Bypass Control
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Solution Overview
Problem
Charge imbalances between battery modules in mixed chemistry batteries reduce the usable capacity and increase the risk of overcharging or discharging, leading to inefficiencies and potential damage.
Innovation Solution
A method involving the use of activation and bypass switches, controlled by a controller, to selectively enable or disable charging of battery modules based on their state-of-charge (SOC) and capacity differences, ensuring balanced charging and discharging across modules with different chemistries like nickel-manganese cobalt (NCM) and lithium iron phosphate (LFP).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If battery modules with different chemistries are connected in series to increase power rating and energy density, then the power rating and energy density are improved, but charge imbalances occur between modules reducing usable capacity
Solution Approach 1:
The controller performs preliminary monitoring of SOC levels for each battery module before charging begins, and preemptively activates bypass switches for modules that would reach full charge first, preventing charge imbalance from occurring in the first place
Solution Approach 2:
Bypass switches are introduced as intermediary components that redirect charging current away from specific battery modules when needed, acting as mediators between the charging system and individual modules to maintain charge balance
2Quantity of substance
If battery modules with different chemistries are connected in series to improve energy density, then the energy density is improved, but the risk of overcharging or discharging increases
Solution Approach 1:
The controller continuously monitors SOC levels of each battery module in real-time and uses this feedback to dynamically control the state of bypass switches, adjusting the charging configuration as SOC conditions change to prevent overcharging
Solution Approach 2:
The system preemptively activates bypass switches when a battery module approaches full charge, preventing overcharging before it can occur by redirecting current in advance
3Reliability
If activation and bypass switches are added to each battery module to enable selective charging control, then charge balance is improved, but device complexity increases
Solution Approach 1:
The controller consolidates the monitoring and control logic for multiple battery modules into a single centralized unit, merging the functions of monitoring and switch control to reduce overall system complexity despite the addition of multiple switches
Data Source
AI summary
Embodiments include balancing modules during charging of a mixed chemistry battery pack having a first battery module connected in series to a second battery module. Aspects include monitoring a first state-of-charge (SOC) of the first battery module having a first battery chemistry and monitoring a second SOC of the second battery module having a second battery chemistry. Aspects also include selectively activating one of a first bypass switch and a first activation switch of the first battery module based on the first SOC and the second SOC and selectively activating one of a second bypass switch and a second activation switch of the second battery module based on the first SOC and the second SOC. The activation of the first bypass switch prevents the first battery module from charging and activation of the second bypass switch prevents the second battery module from charging.