Is there any difference between 18650 lithium batteries with and without protective plates?
What we usually refer to as "18650" actually refers to the external specifications of the battery, which is a standard battery model, where 18 represents a diameter of 18mm and 650 represents a length of 65.0mm. Similarly, 21 in "21700" represents a diameter of 21mm, and 700 represents a length of 70.0mm. These data measure the length of semi-finished battery cells, and many batteries used in practice are equipped with protective plates. Batteries with protective plates are 2.5mm-3mm longer and have a diameter of about 5mm longer than the factory battery cells.
Secondly, what is the main purpose of adding a protective board
Protective board, as the name suggests. A protective plate (with copper or other metal tips welded on the protective plate) is usually added to the negative electrode (bottom) of the battery. From a safety perspective, batteries with added protection boards have basic protections such as over discharge, over charge, over current, and short circuit. Flashlights usually use lithium batteries with plates to prevent circuit short circuits. Of course, flashlights can be turned on and used without batteries, but there is a risk of short circuits.
The difference between having a board and not having a board
Taking flashlights as an example, in practical life scenarios, some flashlights have limited body space, and batteries with protective plates are slightly larger in size, making them less likely to fit into thinner body flashlights, while batteries without protective plates are more flexible. Adding a protective plate will increase the resistance of the battery, so batteries with protective plates will have a slightly lower discharge current compared to batteries without protective plates. Therefore, when using high current and high power scenarios, batteries without protective plates are generally chosen to pursue larger pulse currents. Finally, in terms of cost, the price of batteries with protective plates will be slightly higher than those without plates.
However, batteries with protective plates still have advantages. The probability of explosion caused by improper use and other factors is significantly reduced for batteries with protective plates compared to Dianchi without plates.
In addition, when measuring the length of a lithium battery without a protective plate with a metal measuring ruler, remember to use a piece of paper or other insulation to separate the positive/negative electrode of the battery from the metal ruler to prevent a short circuit between the positive and negative electrodes of the battery.
