Component performance of lithium ion power battery

(1) Open circuit voltage of battery

(2) Internal resistance of battery

(3) Operating voltage of battery

(4) Charging voltage Charging voltage refers to the voltage applied by the external power supply to both ends of the battery when the secondary battery is charging. The basic charging methods are constant current charging and constant voltage charging. Generally, constant current charging is adopted, which is characterized by constant charging current during charging. With the charging process, the active substance is recovered, the electrode reaction area is continuously reduced, and the polarization of the motor is gradually increased.

(5) Battery capacity Battery capacity refers to the amount of electricity obtained from the battery, which is usually expressed in C and expressed in Ah or mAh. Capacity is an important indicator of battery electrical performance. The capacity of battery is generally divided into theoretical capacity, actual capacity and rated capacity. The capacity of the battery depends on the capacity of the electrode. If the capacity of the electrode is unequal, the capacity of the battery depends on the electrode with smaller capacity, but it is by no means the sum of the positive and negative capacity.

(6) One of the main characteristics of chemical power supply is that it can release electric energy when in use and store electric energy when not in use. The so-called storage performance is the charge holding capacity for the secondary battery. For the secondary battery, the service life is an important parameter to measure the battery performance. The secondary battery is called a cycle (or a cycle) after once charging and discharging. Under the corresponding charging and discharging system, the number of times the battery can withstand charging and discharging before the battery capacity reaches a specified value is called the service life of the secondary battery. Lithium ion power battery has excellent storage performance and long cycle life.

(7) The protection circuit consists of two FETs and a specific protection integrated block S-8232. The overcharge control tube FET2 and the overdischarge control tube FET1 are connected in series with the circuit. The protection IC monitors the battery voltage and controls it. When the battery voltage rises to 4.2V, the overcharge protection tube FET1 stops charging. In order to prevent maloperation, the external circuit is generally provided with a extended capacitor. When the battery is in the discharge state and the battery voltage drops to 2.55V, the over discharge control tube FET1 will stop and stop supplying power to the load. Overcurrent protection is to control FET1 to stop discharging to the load when there is a large current flowing on the load. The purpose is to protect the battery and FET. Overcurrent detection uses the conduction resistance of FET as the detection resistance to monitor its voltage drop. When the voltage drop exceeds the set value, the discharge will be stopped. In general, extended circuit is added in the circuit to distinguish surge current and short circuit current. The circuit has perfect functions and reliable performance, but it is highly professional, and it is not easy to buy specific integrated blocks, and it is not easy for amateurs to copy. Because overcharge or overdischarge of lithium-ion power batteries may cause explosion and personal injury, protection is the main concern when using such batteries. Therefore, commercial lithium ion battery packs usually include a protection circuit such as the DS2720 (Fig. 7). DS2720 provides rechargeable lithium ion power battery

All required protection functions, such as protecting the battery during charging, preventing the circuit from overcurrent, and extending the battery life by limiting the discharge voltage of the battery.