protect the LEDs from excessive soldering heat. There are normally current limiting resistors for each LED. They are in series with the devices. Do you have device numbers for the LEDs? Better yet, a specification sheet for them? Somewhere on it will be listed the current rating for your devices. Typical values are 10 to 30 mA. If you try to have more current than that going through them, they will expire so fast, you won't see their death flash. If you have already hitched them to a battery of nearly any size, without using a resistor in series, you will need to replace them.HTH
