How to connect several LED arrays together?

I came across a selection of identical LED torches in my house and was wondering if it would be possible to connect them together to make some form of DIY bike light? I was hoping to connect two or four of them together.

One of the torches was completely duff so i dismantled it to have a closer look at its innards. They run off 3 AAA batteries, so that's 4.5V each. There are nine LEDs on each array but I can't see any resistors. I think the negative terminal battery pack is connected to the casing of the light as there are solder points on the array that aren't directly connected to any of the LEDs.

On the highlighted picture:
Red - Positive LED terminal
Blue - Negative LED terminal
Yellow - Where I believe the +ive LED terminal to conect to the -ive terminal of the battery pack through the casing.

If more information is needed, just let me know and I'll see what I can do. Any help you guys and gals could give me will be greatly appreciated, cheers.

Picture of How to connect several LED arrays together?
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iceng3 years ago

Each of these white LEDs are connected in Parallel, you can do it, BUT see the variations that causes in intensity of identical LEDs.

Led-Box2.jpgLed-Box3.jpg
jtsuhmd3 years ago

the resistor may be connected and hidden in the switch. the LED's are connected in parallel.

Connect the LED modules in parallel.

Meaning, connect all of the positives of the LED modules to each other and connect all of the negative of the LED modules to each other and then connect the positive and negative from the LED modules to the batteries like normal.

You may want to use AA or C batteries for longer life.

I can make a picture if you still don't understand.
I've seen several cheaper flashlight like this. All the LEDs are in parallel, and there are no resistors. I guess they simply apply the parallel connected LEDs across the 4.5V and the current is only limited by the internal resistance of the batteries and the traces.

In the ones I have, the three AAA cells are in a small holder. The tip of the holder is positive, and contacts the center of the PCB. The negative connection is made through the aluminum body of the light itself.

As for using it as a bike light, it might work well as is. These little flashlights put out a fair amount of light. If you want to combine them, I would put a resistor in series with each assembly, and then connect them in parallel (so that pcb and resistor is a "branch"). I would then use a pack of 4 cells of larger size, like AA for 6V. SIze the resistors to limit the current to a safe level for the LEDs. Measure what each assembly draws when connected normally, and chose your resistor to limit to that current.