To determine whether lead-acid batteries require balanced charging, it is necessary to make a comprehensive judgment based on multiple dimensions such as the battery's usage status, performance, and testing data. The core is to identify issues such as "uneven voltage of battery cells" and "inconsistent capacity decay". The following are specific judgment methods, classified and explained according to "intuitive observation", "data detection", and "scene adaptation", covering daily use and professional maintenance scenarios:
1、 Visual observation: Judging from usage phenomena (applicable to non professional users)
Lead acid batteries (especially battery packs composed in series, such as electric vehicles and UPS power supplies) are likely to require balanced charging if the following abnormalities occur:
Fast flashing but short battery life during charging
Phenomenon: The charger quickly displays "fully charged" (green light on), but the actual range significantly decreases during use (such as electric vehicles that used to be able to run 50 kilometers, but now can only run 20 kilometers).
Reason: Some individual cells in the battery pack are "vulcanized" or have capacity decay, causing them to be fully charged ahead of schedule, triggering the charger to trip, while other normal cells are not fully charged, resulting in an overall capacity being "dragged down". It is necessary to activate the vulcanized cells through balanced charging and make up for the undercharged cells.
Abnormal temperature of battery casing during charging
Phenomenon: During the charging process, one of the individual casings of the battery pack becomes noticeably hot (over 40 ℃, with a burning sensation when touched by hand), or the temperature difference between different units exceeds 5 ℃.
Reason: Cells with uneven voltage may experience "overcharging" (high voltage cells will generate heat when charging) or "undercharging" (low voltage cells have low charging efficiency and energy is converted into heat) during charging. It is necessary to balance the charging of each cell to avoid local overheating and damage to the battery.
Sudden power outage/voltage drop during discharge
Phenomenon: During use (such as electric vehicle acceleration, UPS load), the battery voltage suddenly drops from the normal range (such as 12V single discharge end should be ≥ 10.5V) to a very low level, causing the equipment to shut down.
Reason: There are "lagging cells" (with much lower capacity than other cells) in the battery pack. The cell is discharged first, triggering an overall voltage drop. The lagging cells need to be repaired through balanced charging to level the capacity of each cell.
2、 Data detection: Judging from key indicators (applicable to professional maintenance or scenarios with detection tools)
Obtaining data through tools such as multimeters and battery testers is the most accurate way to determine the demand for balanced charging, with a focus on "cell voltage difference" and "capacity consistency"
1. Core indicator: Individual voltage imbalance (the most direct judgment basis)
The key requirement for lead-acid battery packs (such as 48V electric vehicle batteries consisting of 4 12V cells connected in series) is that all cell voltage deviations must be ≤ 0.05V (at the end of charging) or ≤ 0.1V (at the end of discharging). If this range is exceeded, balanced charging must be performed.
Specific testing steps:
① Before charging: Measure the total voltage of the battery pack, then measure the voltage of each individual cell one by one, and record the difference; If the voltage of a single unit is more than 0.1V lower than the average value, it indicates that the unit is undercharged.
② At the end of charging (1-2 hours after the green light of the charger lights up): Measure the cell voltage again. If the voltage of a cell exceeds 13.8V (12V cell) or is lower than 13.2V, it indicates that the voltage is unbalanced (too high is overcharging, too low is undercharging).
Example: At the end of charging a 48V battery pack (4 sections of 12V), the normal cell voltage should be 13.3-13.5V. If a section is 12.9V and a section is 14.0V, with a deviation of more than 0.1V, balanced charging is required.
2. Auxiliary indicator: Poor consistency of capacity
If there is a "battery capacity tester", it can be determined through discharge testing:
Method: Discharge the battery pack at the rated discharge current (such as 0.5C current for electric vehicle batteries, 10A current for 20Ah batteries) until the cut-off voltage (12V cell cut-off voltage 10.5V), and record the "discharge time" of each cell.
Judgment: If the discharge time of a single cell is more than 20% shorter than other cells (such as a normal cell being discharged for 2 hours and a single cell being discharged for only 1.5 hours), it indicates that the capacity of the cell has declined and needs to be repaired by balanced charging.
3、 Attention: Avoid "over balanced charging"
Although balanced charging can fix the problem of imbalance, it is not necessarily better to have more:
Frequency: In regular usage scenarios, there is no need to balance every charge. Excessive balancing can lead to overcharging of the battery and accelerate plate aging;
Duration: The typical time for a single balanced charging is 6-12 hours (depending on the charger power, with a stable single cell voltage of 13.5-13.8V), and should not exceed 24 hours to avoid electrolyte dehydration.
In summary, the core logic for determining whether lead-acid batteries require balanced charging is to first make a preliminary judgment through "intuitive phenomena", then accurately confirm it through "single cell voltage detection", and finally regularly prevent it based on "usage scenarios". The essence of balanced charging is to 'recharge' under charged cells and 'limit current' over charged cells, ultimately achieving synchronized performance of the battery pack and extending its overall lifespan.
