Parallel Battery Charger Current Equalization
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Solution Overview
Problem
Charging multiple batteries in parallel results in uneven current distribution due to varying open circuit voltage and internal resistance, leading to prolonged charging times and potential safety issues when exceeding maximum allowable current.
Innovation Solution
A method and charger that control battery charger output current to equalize charging current by detecting and adjusting the current difference between each battery and the maximum allowable current, ensuring all batteries reach a safe maximum charging current efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sequential switching between batteries is used to charge each battery individually, then each battery can be charged under ideal conditions without exceeding maximum allowable current, but the total charging time becomes extremely long
Solution Approach 1:
The patent segments the charging control by individually monitoring the charging current of each battery through separate current detection circuits, while managing them as a parallel group. This allows simultaneous charging of multiple batteries with individualized current control, resolving the contradiction between safety (sequential charging) and time (parallel charging).
Solution Approach 2:
The patent implements feedback control by continuously detecting the charging current of each battery, comparing it with the maximum allowable current, and adjusting the charger output current accordingly. The control unit reduces the output current when any battery approaches its maximum limit, ensuring safety while maintaining parallel charging efficiency.
2Productivity
If batteries are charged in parallel with high output current to reduce charging time, then charging speed increases, but the charging current exceeds the maximum allowable current of individual batteries causing safety issues
Solution Approach 1:
The patent employs dynamic current control where the charger output current is not fixed but continuously adjusted based on real-time battery states. The control unit dynamically reduces the output current when detection shows any battery approaching its maximum allowable current, enabling the system to operate at high productivity when safe and reduce when necessary to maintain reliability.
Solution Approach 2:
The patent changes the operating parameter (charger output current) based on battery conditions. By monitoring individual battery currents and adjusting the overall output current accordingly, the system optimizes charging speed while preventing any single battery from exceeding its safe current limit, thus resolving the productivity-safety contradiction.
3Productivity
If batteries with different internal resistance are connected in parallel and charged, then parallel charging is enabled, but charging current becomes uneven with low internal resistance batteries receiving excessive current
Solution Approach 1:
The patent applies local quality control by implementing individual current detection and control for each battery in the parallel connection. Rather than treating all batteries uniformly, the system monitors and controls the charging current of each battery separately, accounting for differences in internal resistance and ensuring each receives appropriate current within its safe limits.
Data Source
Figure 1(B1)~1(B3)
Figure 2(B1)~2(B3)
Figure 3
AI summary
The method for charging parallel connected batteries and parallel connected battery charger safely and rapidly charge a plurality of batteries connected in parallel. After initial charging with battery charger output current set to a minimum charging current (Imin), detected charging current is compared with the maximum allowable current (Imax) for each battery. Without detected charging current (Id) exceeding the maximum allowable current (Imax) in any battery, battery charger output current is gradually increased to make charging current in the battery with the smallest current difference (IΔ) between detected charging current (Id) and the maximum allowable current (Imax), namely the battery with charging current closest to Imax, equal to the maximum charging current (Ic) for safe charging, and thereby charge each battery simultaneously