Methods 1 and 18650 lithium batteries were 650mm long, and a circular protective plate was installed at the negative electrode when it exceeded 1mm;
Method two. Immediately test the short-circuit current of 10A or 20A lithium battery with ammeter. If the ammeter instantly reads zero, it means that the 18650 lithium battery has a protective plate. If the ammeter reads a lot or shows overload, the battery has no protective plate or the protective plate is invalid.