Voltage and total resistance in the circuit. The voltage of a lithium battery is determined by the battery itself, i.e. the electromotive force. Current is related to battery voltage and total circuit resistance. The charger only determines its own rated output current during design. but during the charging process, the size of the charging current is related to the saturation state of the battery. If it is an ordinary lead-acid battery and charger, the charging current is largest when it is off as the power increases. , the voltage increases and the current slowly decreases until it is full. Specific batteries and chargers have different characteristics. In a different way, the charger will sense the battery voltage to determine the battery's state of charge and determine how much current to use.
How to measure the quality ofs lithium batteries? How to test the quality of lithium batteries
The charging current of lithium batteries is determined based on the capacity. The higher the current, the more difficult it is to fully charge the battery. This is done to protect the lithium battery from normal use, as overcharging and overdischarging can cause the lithium battery to leak, malfunction, or even explode.
In terms of the charging current of the lithium battery fast charging stage during the charging process, as a dynamic process, the optimal charging current of the lithium battery is actually divided into three stages.
1. The optimal current during precharge: That is, when the initial/no-load voltage of the lithium battery is lower than the precharge threshold, it should first go through a precharge stage. Only one lithium-ion battery is affected. This thresholdl is usually 3.0 V. At this stage, the precharge current is about 10% of the current of the next stage - the constant current charging stage.
2. The optimal current during constant current charging: The so-called constant current means that the current is constant, the voltage gradually increases and at this time it enters the fast charging phase. Most constant current charging current settings are between 0.4 and 0.6 C, which can be understood as 0.5 C, which means it can be fully charged in about two hours without holding take other factors into account. The reason 0.5C was chosen is that this current is a good balance between charging time and charging safety.
3. Charging current during constant voltage charging: For a single-cell lithium-ion battery, when the battery reaches a certain voltage value, it enters constant voltage charging. This value ofvoltage is generally 4.2V. step, the voltage remains unchanged, and the current decreases; this current reduction is a sequential decreasing process. Most lithium battery protection chooses 0.01C as the termination current, which means that the charging process enters the final state. After charging is completed, the charging current drops to zero.
The core of the optimal charging current for lithium batteries is the current design during constant current charging. It is worth pointing out here that most portable lithium batteries are preferably designed for 0.5C charging, like conventional 18650 lithium batteries. The capacity is 1800-2600mAh and 1A charging can be selected, while the rate type is 1200-1500mAh and 0.5C charging current is 0.7A Strictly speaking, the maximum charging current of lithium batteries is determined by the structure.battery life. Therefore, various lithium battery manufacturers have inconsistent regulations. Some are set at 0.6 C, and the highest regulation for portable lithium batteries is 1 C.
How to calculate the charging current of a lithium battery?
The maximum charging current that lithium batteries can accept is generally 1C or even less. The charging current of lithium batteries is usually indicated on the charger, usually lithium batteries use constant current first and then. In constant voltage charging mode, when the charger reaches the charger limit voltage, trickle charging will be carried out, so the charging time will be added to about 1 hour. If you want to calculate the charging time, divide the battery capacity by. the charging current, and add the upconversion loss is almost the same after adding one hour.
Lithium iron phosphate batteries can generally use a charge and discharge current of 1C or more (15C), so they are more suitable as power batteries. The theory of 18650 battery charging time is the same as all secondary battery charging time, that is, the battery charging time is equal to the ratio of rated capacity to the charging current. However, due to the internal impedance generated during the operation of lithium batteries. charged, the charging time of the 18650 battery must be taken into account to overcome this impedance factor.
1. The quickest inspection method is to test the resistance and maximum discharge current. Good quality lithium batteries have very low internal resistance and high. maximum discharge current. Use a multimeter with a range of 20 A and directly short the two electrodes ofthe lithium battery. The current should generally be around 10A or more and can be maintained for a while. A relatively stable battery is a good battery. .
2. Look at the appearance. The fullness of the appearance, such as the general lithium battery of about 2000 mAh, is relatively large. The finish is finer or the packaging is more complete.
3. Look at the hardness. You can gently or moderately pinch the middle part of the lithium battery with your hands. If the hardness is moderate and there is no feeling of softness and compression, it proves that the lithium battery is a relatively high-quality battery.
4. Look at the weight. Remove the outer packaging and feel the weight of the battery to see if it is relatively heavy. If it is heavy, it is a high quality battery.
5. During the battery charging process au lithium, if the battery poles do not heat up after continuous discharge for about 10 minutes, it proves that the battery protection board system is complete, usually with high quality protection boards. The quality of lithium batteries is better than ordinary lithium batteries.