Whats the highest voltage & current i can supply to 5x XM-L T6 LEDS?

Hi everyone. This is my very 1st post and I am new to this whole LED Technology.

I bought a 7000lm bike light that has 5x MX-L T6 leds. It came with a 8.4V, 6.4Ah battery pack. When i tried it, i compared it to a number of retail store led lights I bougt and my new light certainly didn’t produce 7000lms with the 8.4V, 6.4Ah battery pack supplied. It only produced around 1600 - 2000lms, comparing it with the other led torches we had.

I pulled the battery pack apart and each of the 4x 18650 batteries tested (with a voltmeter) are 4.2V, and 3.2Ah. The configuration of 2pairs of batteries in parallel, then each pair connected in series gives the 8.4V & 6.4Ah.

As i stated above, im new to this technology so i dont know how many volts or amps i can drive into this light without blowing the leds? Soooooooo………

Q.1. I was wondering, if i was to use a bigger battery pack(or made one up) with more voltage & amps, would that enable me to get the 7000lms?

Q.2. What would be the maximum voltage & amps I could use?

I would realy appreciate your help. Im scared of blowing the leds if i use too much voltage and amps!

Thank you in advance :slight_smile:

Read dis: http://flashlightwiki.com/Driver ;)

(a 5x XML bike light is probably using a boost driver, to take the high current/low voltage from the battery pack and convert it into a high voltage/low current to drive the series string of LEDs)

Thank you comfychair for that link. I wont even pretend to say i understood it all lol

The reason i believe im not getting the full 7000lms is, i found the same light configuration on ebay ‘in a torch’ and in the specs, it said those MX-L T6 leds can take anything from 7.2V up to14.8V. (Is that correct? Can all MX-L T6 leds take up to 14.8V?)

They also supply a ‘6x 18650 battery pack’ rather than the ‘4x pack’, stating it was more powerful than the standard 4x pack. So hence why im thinking, if i connected the light to say, a 12V battery, would that give me close to the 7000lms?

In the link you gave, i know it talked about the possibility of burning out the chips if too much current/voltage is applied, but thats the problem. I dont no how much is ‘too much!’
If the specs from the ebay light are correct, maybe i can apply volts up to 14.8V. I dont think ill be brave enough tho to try it at 14V lol but i might be tempted to try 12V lol
Thank you again for your reply :slight_smile:

Which light? Link?

First off, I would look to see if all of the leds are in series. If so, then the driver would most likely be a boost driver.

Will the driver take higher voltage? Seriously doubt it. Only way to know would be to talk to the manufacturer and that's not going to happen, (most likely). Probably like many Chinese made lights, it's rated several times above actual output. That's called salesmanship right there.

To get close to the amount of lumens you want, it would most likely take a different driver. We would have no way to know how many volts the driver takes, without having some detailed photos of the driver and maybe then, it might be unsure. Best to assume that the driver is a boost driver and won't take higher voltage.

What the driver (chip) can handle and what the emitters (led’s) can handle are two different things. What you don’t want to do is change your voltage without knowing if your driver can handle it. Most likely it can’t.

Lumens are almost always exaggerated by vendors, even most good vendors exaggerate lumens. They might not have any idea what it’s actually putting out.

If you want to get more lumens out of this light without changing the driver you can try and lower the resistance by putting heavy gauge wire on. This often helps. Thin wires make it hard for electricity to travel, creating resistance. You might also be able to mod the driver itself without too much trouble. However, for us to help you will need to post pictures of the driver.

Good luck and welcome to BLF.

on one bikelight head i think for cooling you need water cooling or bicycle by hard frozen.

it become hot after short time.

The purpose of the driver is to take a variable input (battery pack voltage starts out at 8.4v freshly charged, falls to 6v when empty), and convert it to a constant output. Well, a good driver will do that, some designs pretend to try but just aren't very good at it.

If your driver is doing what it's supposed to do, increasing the input voltage won't affect the output.

If you still want to try tweaking it you'll have to take it apart. Get good crisp clear photos of the driver, and figure out if the LEDs are wired in series or parallel. Unless someone here has already done the reverse engineering on the exact same light you'll have to get that info for us.

Hi Guys,

WOW! I was thinking when I first wrote my situation, I was gonna get an easy solution lol This is way way over my head lol
Thank you guys so much for your replies….I sincerely appreciate it :slight_smile:

As I said above, I’m new to this LED Technology and I’m realising it’s not as simple as going out to buy a 100W bulb or 150W bulb lol

I’m a bit scared to try a bigger battery now! The light was advertised as a 7000lm light, but it’s far from it. Oh well, you win some - you lose some! It certain makes you not trust the adds for lights regarding their ‘lumens’

I have decided to just stick with the battery pack I got with the light, to be on the safe side.

Again thank you all so much :slight_smile:

Kind Regards from down under, New Zealand :slight_smile: