The voltage of a single lithium battery is generally 3.7V. If you want a high-capacity battery, you generally need to increase the capacity in parallel. For example, the 20000mah of a mobile power supply is generally composed of 8 2600mah batteries or 6 3400mah 18650 batteries.
In the process of battery use, a single battery often wears out much first. Just like the short board principle of a wooden barrel, a battery or a group of batteries connected in parallel affects the total battery voltage and capacity of the entire battery pack.
If this happens, the battery pack must be replaced at this time to avoid the barrel effect (short board principle-the barrel can hold water depending on the shortest board). Only in this way can the battery be used in a balanced manner and extended use.
If this kind of problem occurs, you should measure the voltage at both ends of each group of batteries one by one, remove the battery that has no voltage or the voltage is seriously low (a single battery is described above), and replace with a new battery of the same type and similar internal resistance.
At present, all lithium battery repairs on the market use the method of replacing a single battery! Other methods have no effect at all! In addition, the lithium battery must be equipped with a protective plate in use to limit overcharge, overdischarge, short circuit, etc., which is beneficial to prolong the life of the lithium battery pack.