I have a bunch of LEDs, all colors, no part numbers, no information. They probably all need a different value resistor to connect them to a battery. Probably very low light LEDs.
I know if you connect a 100w 120v light bulb in series with a 60w 120v light bulb then connect them to 240v the 60 light will burn out. Same thing with heating elements.
LEDs are not very forgiving.
I have several Harbor Freight free flashlights those things are junk they last about 1 week and stop working. They have 9 LEDs on a circuit board that light up on 3 AAA batteries. Circuit board shows all 9 LEDs are in parallel with no resistors.