Method 1: The length of a 18650 lithium battery is 650mm, and over 1mm, a circular protective plate is often installed at the negative electrode;

　　Method 2: Use a 10A or 20A ammeter to momentarily test the short-circuit current of the 18650 lithium battery. If the ammeter instantly reads and quickly turns to zero, it indicates that the 18650 lithium battery has a protective plate. If the ammeter has a large reading or displays overload, the battery does not have a protective plate or the protective plate is invalid.

　　What is the function of a protective board for a single battery cell?

　　The protective board actually means to protect the battery, and the protective board of a single battery generally plays a safety protection role.

　　Not only 18650 lithium batteries, but to be precise, all lithium batteries need to be used, mainly for overall management of battery overcharging, discharging, short term protection, etc. You are probably the same reason as water and container. When the faucet is turned on (battery charging), without protection, if the faucet is not turned off, water will continue to flow into the container (charging). When the container cannot be filled, it will still flow in and water will overflow.

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