Internal resistance of a battery cell is a core indicator for measuring battery performance and safety. For power batteries from companies like Guoxuan High-Tech, low internal resistance means less heat generation, higher charging efficiency, and longer lifespan. If the internal resistance is too high, the battery is not only prone to overheating during charging and discharging, but may also trigger serious safety hazards such as thermal runaway.
Why is internal resistance so important?
Heat Control and Safety: A battery is like a water pipe, and internal resistance is like the grime inside. According to Joule's law (Q = I²Rt), current flowing through a resistor generates heat. The lower the internal resistance, the less heat is generated, and the safer the battery. Guoxuan High-Tech has significantly reduced the DC internal resistance (DCR) of its cells through technologies such as three-dimensional conductive networks to control heat generation during fast charging. Energy Conversion Efficiency: Energy is lost due to internal resistance during charging and discharging. According to Ohm's law (U = E - Ir), low internal resistance ensures a more stable output voltage and higher energy utilization. Fast Charging Performance: High-rate fast charging requires the battery cell to be able to quickly withstand large currents. Low internal resistance cells effectively reduce voltage drop, preventing rapid battery temperature rise due to high-current charging and enabling rapid energy replenishment.
Guoxuan Battery Cell Resistance Reduction Technology
To overcome internal resistance limitations, Guoxuan High-Tech has adopted several key technologies in battery design: Multi-tab design: Increases current path, shortens electron transport path, and directly reduces ohmic internal resistance.
Nano-sizing and carbon coating: Improves electrode conductivity and reduces electrochemical polarization internal resistance through nanoscale material processing and coating technology.
Types and Influencing Factors of Internal Resistance
Battery internal resistance mainly consists of two parts:
Ohmic internal resistance: Determined by electrode materials, electrolyte, separator, and component contact.
Polarization internal resistance: The resistance generated when current passes through the electrodes (including electrochemical polarization and concentration polarization). Internal resistance is not constant;
It is affected by the following factors:
Temperature: Lower temperatures increase electrolyte viscosity, slow ion movement, and significantly increase internal resistance.
Aging degree: As the number of battery cycles increases, internal materials are depleted, and internal resistance gradually increases.
Understanding internal resistance helps in assessing a battery's State of Health (SOH).
Three Practical Benefits of Low Internal Resistance: This seemingly small value hides the battery's 'health code':
Heat Control: At 1C discharge, a 1mΩ internal resistance generates 75% less heat than a 2mΩ internal resistance cell.
Efficiency Improvement: After 200 cycles, low internal resistance cells retain 8% more capacity.
Instantaneous Response: Voltage drop is reduced by 40% when starting a 500A pulse current.
It determines discharge power: Current flowing through internal resistance generates heat, resulting in energy loss.
Low internal resistance allows the battery to discharge at high currents (e.g., during racing car acceleration). It reflects battery health: Internal resistance gradually increases with battery aging. It is widely used to assess battery SOH and estimate remaining capacity.
It affects heat generation and safety: High internal resistance cells accumulate significant heat during high-power operation. Excessive temperature can lead to thermal runaway (fire or explosion).
II. Impact of Cell Packing
When dozens or even hundreds of cells are connected in series and parallel to form a battery pack, the consistency of internal resistance (all cells having similar internal resistance) is crucial in determining the battery pack's lifespan. Capacity bottleneck effect: The overall capacity of the battery pack is determined by the worst-performing cell.
Consequences: If a high-resistance cell is mixed into the pack, that cell will deplete its charge prematurely, leading to a shortened driving range for the entire battery pack. Accelerated vicious cycle (uneven heating): Cells with low resistance are like "highways," allowing current to flow smoothly. Cells with high resistance are like "narrow mountain roads," generating significant heat when current flows through them.
Consequences: Cells with high internal resistance reach higher temperatures during charging and discharging, and these high temperatures further increase internal resistance. Over time, this cell will age faster and eventually damage the entire battery pack. Low charging and discharging efficiency: When charging the battery pack, high-resistance cells will fully charge prematurely and generate polarization voltage, causing the charging system to terminate fast charging prematurely. Consequences: The charging time for the entire battery pack increases, and system efficiency is significantly reduced. Voltage unevenness causes abnormalities in series circuits where the current is the same. According to the formula U=IR (voltage = current × resistance), the voltage drop across a high-resistance cell is greater.
Consequence: This leads to inconsistent voltages among the cells in the battery pack during operation. Some cells may prematurely reach overcharge or over-discharge states, triggering the Battery Management System (BMS) to report an error and shut down.
III. Engineers' Countermeasures To avoid the aforementioned effects after assembly, manufacturers perform "sorting and grouping" at the factory. They use professional battery internal resistance testers to select cells with highly consistent internal resistance, capacity, and voltage for assembly, thereby maximizing the battery pack's lifespan and safety. If you are considering assembling a battery pack or evaluating the health of electric vehicle/energy storage batteries, we can discuss this further.
