A battery pack is formed of battery cells whose charge / discharge efficiency directly reflects the battery pack capacity and lifespan. As the battery cells conditions are varied slightly when manufactured, the cell voltage and capacitance are easily unbalanced as a result of current and temperature difference that caused by battery pack location. This reduces the battery pack efficiency, and gets worse as time goes by.
Furthermore, voltage difference may occur due to different battery self-discharge rate as the battery modules are often stored for a long time during manufacturing process. It is necessary to perform balance and capacity inspection before assembling the battery pack.
The table lists the measured capacities of an electric motorcycle battery pack already used for six months that discharges from 4.15V to 3.0V, in which the impact of a battery cell’s DC resistance to the capacity can be easily determined. In practical use, the battery pack can no longer be used if one of the battery cells stops discharging due to poor capacity even though the rest of the battery cells still have power. The built-in BMS will warn the battery pack not to discharge any more.
To deal with this kind of problems, a tool that can diagnose and repair the cell imbalances is required. Chroma ATE Inc. uses the 8700 ATS as the platform to launch a battery maintenance and diagnosis solution that can not only solve the battery imbalance problem but also have efficient and comprehensive testing capabilities.
1. Completing automatic test program with one button
The system can automatically complete the adjustment based on the battery cell voltage set by the user without any manual operation except waiting for the test results.
2. Test reports
All test conditions and results can be generated into a report so that the defect cells can be easily found. The user can define and customize the report format as desired.
3. Exclusive test items
- DC resistance measurement
- Capacity test for each cell
- Battery cell balance test
The DC resistance measurement/capacity test helps understanding the battery cell condition while the battery cell balance test makes the unbalanced cell voltage to balance again. On the contrary, this function can also be used to create battery cell imbalance condition for conducting voltage imbalance (such as UL2271) testing.
The Chroma 8700 can rapidly diagnose the battery cell status, and significantly extend the battery life cycle. It is applicable for product routine maintenance or battery pack inspection before assembly. It can bring significant benefits to battery manufacturers for quality improvement, and give end users more protection.
Detailed product information: Battery Pack Functional ATS Model 8700