bizarre christmas lights....

[Dualfuel]

Hi,
This topic definitely falls in the "...if you don't know where else to put it..." category.
I bought two 100 LED strings of lights. They are the Volt hawk brand that use 4 D cell batteries. Mr. Wil E. Coyote here, thought if I jumpered them up in series they'd work off of a 12volt car battery. So I bravely voided the warranty by soldering a jumper wire between the two battery boxes... Then I wired up my battery. Nothing. No smoke, no lights, nothing at all. I probed the wires running to the lights and got six volts on each string. No lights. I let it sit for a while. I desoldered the wire, and installed the 4 D cell batteries. Still nothing. Still had six volts running up and down the light"s wires.
After deciding that I was not going to drive 200 miles to argue and exchange the lights, and that I had hopelessly voided the warranty, I started cutting apart the wire string. Turns out that 5 diodes in series will light up on a 12volt battery, but the strings were built with 10 diodes in series. So I added a second 12volt battery and wella!! Happy Kinder! the Christmas lights are working.

So what I think happened is that when I wired them in series I must have blown some component.

Is it possible that these lights have a small mppt controller taking 6vdc and pulsing it to the LEDs at 24vdc?

https://www.google.com/#q=volt+hawk+christmas+lights&tbm=shop&spd=7455822854561589389

dunno but it sure was a mind bender...
BPJ

[Thob]

Lesson 1: Verify that it works BEFORE you modify it...

Lesson 2: LEDs are a strange animal.  They are not linear in their current vs voltage relationship.  Incandescent bulbs act more or less like a resistor that is linear, a little more voltage and they draw a little more current and they are a little brighter.  LEDs are diodes that operate in the forward biased condition.  That means that they draw little or no current at low voltage.  As the voltage is increased, they suddenly start conducting and begin to glow.  After that, the curve gets pretty steep and a little more voltage can cause a lot more current to flow.  The exact operating point depends on the color of the LED and varies somewhat with manufacturing processes.  For this reason, the proper way to operator a LED is on a constant current controller.  Compromises can be made by operating the LED with a series resistor that limits the current.  A lot of the cheap LED flashlights rely on nothing more than the limitations of AAA batteries to limit the current.

What color are the LEDs you bought?  Red LEDs run around 1.75 volts, blue/white at 3.2 volts.  Other colors at corresponding voltages in between.

There is probably a lump in the battery box or in the wiring somewhere that contains a magic circuit for running your LED lights.