Black Hole
May contain traces of nut
I've discovered that a 20-LED string, powered by a two AA battery holder with switch, bought from my local discount store for 99p (!), has the LEDs in parallel and no current limiting resistor - relying on the internal resistance of the batteries to bring the operating voltage down to about 2.5V. Fortunately NiMH rechargeables would only kick out 2.4V-ish, otherwise their lack of internal resistance would make them a hazard in this scenario.
A similarly cheap string, this time with a holder for 3xAAA, has a 10Ω series resistor. I think the Chinese makers of this crap decide by trial and error.
A similarly cheap string, this time with a holder for 3xAAA, has a 10Ω series resistor. I think the Chinese makers of this crap decide by trial and error.