LED conversion of big old rechargeable spotlight

[weltenbummler]

I was trying to convert this big old flashlight I found into a more mordern and powerful LED flashlight. I recently replaced the battery and since it can be charged by plugging it into a regular power outlet it is actually quite convenient and just needs an upgrade.

I figured it would be quite simple by ordering these LED light bulb replacements from ebay. It actually works quite well with the smaller 6-LED E10 light but it did not give me enough light. Therefore I bought a 16-LED E10 light from the same seller. It says on the light that it can be used with 6V-9V. Since the battery is 6V, I thought I should be good to go and it will produce as much light as possible.

I seem to be missing something here (most likely basic skills as an electrician) because the light the 16 LED E10 light gives me is considerably less than what the 6 LED E10 light produces. I guess I have to adjust some resistor on the circuit board.

Can someone help me identify the parts that need modification and point me to the right direction?

(I hope I posted this in the right category...)

 

[manishanand14]

Most probably the LED array which you have bought must be connected in parallel.I guess it is 5mm white LED.Each LED need 20-25mA rated current for proper glow.
I guess R94,R95 are current limiting resistors.

You first connect 16LED array directly to the battery[as LED array is 6-9V rated] and measure how much current it is drawing using a multimeter[Set the multimeter in current measuring mode in series with the LED array and battery]

Then again measure the current in the circuit and notice the difference.You will probably get an idea how much more current you need and accordingly adjust the resistance.

 

[weltenbummler]

You first connect 16LED array directly to the battery[as LED array is 6-9V rated] and measure how much current it is drawing using a multimeter[Set the multimeter in current measuring mode in series with the LED array and battery]

I did that and connected it even directly to the battery, but it is still very weak. Does that mean it might not be connected in parallel? I was not able to measure the current, because I don't have access to a multimeter right now.

I am quite a novice when it comes to electronics, but just to help my understanding: The, actually quite big and heavy, battery should provide more than enough power make the LEDs go real bright, right?

EDIT:
I found the following in the description of the array:
6V + 1m distance = 35Lux
7.5V + 1m distance = 130Lux
9V + 1m distance = 300Lux

Also there are actually 19 instead of 16 LEDs and the circuit looks like this:

 

[manishanand14]

If it is not giving off enough light even when it is directly connected to the battery then you probably can't use it in your circuit.I guess several series LED array are connected in parallel.Your battery[6V] can deliver enough current for LED lighting.The problem lies in your LED array.

Make sure that the battery is fully charged.

Get a basic multimeter even if you are a beginner.

One other thing you can do is to build your own LED array.You can connect 2 white LEDs[10mm] in series and several series combinations in parallel to make your own LED array.

 

[weltenbummler]

Can't I change the existing array to accommodate for my battery?

 

[manishanand14]

It's difficult because the LED array you have has surface mount resistors.

Can you provide the front picture of the LED array showing all the LEDs because I can only count 11 surface mount resistors.

 

[weltenbummler]

After counting again, it turns out that there are actually 20 LEDs on the array. That means even the seller got it wrong in his shop...

**broken link removed****broken link removed**

 

[manishanand14]

You didn't tell the correct no. of LEDs???????????????? in the beginning.

 

[weltenbummler]

You didn't tell the correct no. of LEDs???????????????? in the beginning.

I recalled 16 from memory, the description of the item says 19, but there are actually 20. Is that a problem?