Analysis of Lithium Battery Tester

With the development of the times, people’s demand for communication equipment, digital products, power tools, electric vehicles, etc. is increasing, and these demands for large-capacity batteries are also expanding, making the entire battery industry prosperous and prosperous. development of. Because of this, everyone has paid unprecedented attention to the battery, and its safety, durability, and reliability are huge challenges. How can we know the performance of the battery? Today, Chuangfa will let you know about the lithium battery tester and how it tests the battery. Today we take the N6705B DC analyzer as an example.

Main features of N6705B DC analyzer:

•1~4 high-performance power supplies/loads

•digital voltmeter and ammeter

•Arbitrary waveform generator with power output

•Oscilloscope

•Data acquisition

•All measurements and functions can be realized through the front panel

The first method to use N6705B for cell/finished battery capacity test, that is, it is used as a power source or load to directly charge, discharge, and test the capacity of the battery. As shown in the figure, the PC installs 14585A software to change the voltage and current with time. And directly display the capacity value. The software supports up to 999 hours of long-term recording, and can perform any area zoom in, zoom out and analysis functions.

The second method is to use N6705B for cell/finished battery capacity test, that is, use a real charger and mobile phone to charge the battery, as a voltage and current meter to test the charging capacity, as shown in the figure 4 shown. The charging model of mobile phone charging is completely different from the charging model that is directly charged by the power source, and it reflects the battery capacity most truly. Unlike any other method, the ammeter of the N6705B achieves a 0V voltage drop without any impact on the battery voltage.

The third method is to use N6705B for cell/finished battery capacity test, that is, use a real mobile phone to discharge the battery and use it as a voltage and ammeter to test the discharge capacity.

The internal resistance of a battery refers to the resistance of the battery when the current flows through the battery. It includes ohmic internal resistance and polarization internal resistance. Polarization internal resistance also includes electrochemical polarization internal resistance. Resistance and concentration polarization internal resistance. The AC internal resistance test method is: using the battery's equivalent to an active resistance, give the battery an alternating current of 1000Hz, amplitude 50mA, and a series of processing such as voltage sampling, rectification and filtering to accurately measure its resistance.

Battery protection circuit board testing also has many challenges. There are many protection circuit test items, and both the B+ and B- terminals, or the P+ and P- terminals are 'bidirectional. Usually, multiple power supplies, electronic loads, oscilloscopes, programmable switches, etc. are required to complete the combination. The connection block diagram of the test system is shown in Figure 6. The accuracy requirements of the test equipment are extremely high. For example, the overcharge voltage protection test requires the voltage accuracy of the simulated cell to reach a few mV. Therefore, at a voltage of 4V, 1mV is equivalent to 0.025%. Similarly, the idle current of the protection circuit board is only a few μA, which usually needs to be tested with a multimeter. The resistance of the protection circuit board is only a few mΩ or tens of mΩ, which also puts high requirements on the test equipment

Only one N67xx power supply can complete the battery protection circuit board. Test items include: charge overcharge protection voltage accuracy and response time, overcharge protection cancellation recovery and response time, discharge overdischarge protection voltage accuracy and response time, overdischarge protection cancellation recovery and response time, charge overcurrent protection and response time , Discharge overcurrent protection and response time, standby idle current, resistance of the protection circuit.

Using N6705B's arbitrary waveform generator function, channel 1 simulates the rising and falling sequence of battery voltage, detects current changes, uses oscilloscope function to record voltage and current changes at the same time, and can test charging overvoltage protection voltage and response time , Protection and cancellation of battery voltage and response time.