Battery Internal Resistance Tester: How to Assess Battery Health
Key Points
- Battery capacity typically drops below 80% when internal resistance increases to 1.5–2 times its initial value.
- AC injection test speed under 1 seconds, accuracy up to 0.01 mΩ
- Power systems should be tested every six months. Cells with internal resistance exceeding the average by 50% require close monitoring.
Battery internal resistance is a key indicator for assessing the State of Health (SOH) of lead-acid batteries. An increase in internal resistance indicates reduced capacity and accelerated aging. This article explains the principles, methods, and application scenarios of battery internal resistance testing.
Relationship Between Battery Internal Resistance and Capacity
Battery internal resistance consists of ohmic resistance and polarization resistance. Ohmic resistance arises from the electrodes, electrolyte, and separator. Polarization resistance results from charge transfer and diffusion during electrochemical reactions.
New batteries typically have internal resistance in the milliohm range. As charge-discharge cycles increase, internal resistance gradually rises. When it reaches 1.5-2 times the initial value, battery capacity usually drops below 80%, indicating it's time to replace the battery.
## Internal Resistance Testing Principle
AC Injection Method: Injects a 1 kHz AC signal into the battery, measures the voltage response to calculate internal resistance. Fast testing (under 1 seconds) without affecting normal battery operation. Le Xin Electronics Technology (Baiantu)'s battery internal resistance tester uses the AC injection method with accuracy up to 0.01 mΩ.
DC Discharge Method: Briefly discharge the battery with high current, then measure the voltage drop to calculate internal resistance. Offers higher accuracy but affects battery operation; best suited for offline testing.
## Typical Use Cases
Power System: Perform routine maintenance on substation DC screen battery groups by measuring the internal resistance of each cell to promptly identify deteriorating batteries. Recommend testing every six months; cells with internal resistance exceeding 50% above the average should be closely monitored.
Communication Base Station: Maintain the UPS backup battery pack to ensure seamless switchover during power outages. Base station batteries typically require internal resistance consistency within ±10%.
New Energy Vehicles: State of Health Assessment of Traction Battery Packs. Internal resistance data is used in the BMS (Battery Management System) SOH algorithm.
Data Center: In UPS battery maintenance for server rooms, internal resistance testing is a core preventive maintenance activity.
Recommended Testing Frequency
When a new battery is put into service: establish baseline internal resistance data.
Within the first 1 years of use: Inspect every six months.
In use for 1-3 years: Inspect quarterly.
In use for 3+ years: Inspect monthly.
Le Xin Electronic Technology offers portable and benchtop battery internal resistance testers, covering all scenarios from field inspections to laboratory precision testing.
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