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Thread: LF2XT Mod Issues - Lots of HEAT

  1. #1
    Flashaholic* ShineOnYouCrazyDiamond's Avatar
    Join Date
    Aug 2009
    CT, USA

    Default LF2XT Mod Issues - Lots of HEAT

    I am looking to see if I am the only one who has experienced this issue. I have 2 LF2XTs. I moded the LED in the first one to a Nichia 219 HiCRI led and it has been working fine on both NiMH and 10440 LiIons.

    The problem occured when I modded the other one to a XP-G led. It appeared to be working fine on NiMH cells, but the runtime was notably shorter than that of the Nichia. Also, the ODP protection on high would start flashing the LED periodically even after just 5-10 minutes of runtime. When running it on a 10440 all seemed well until I went to high. On 10440 High the body of the light got too hot to barely touch in about 10 seconds. Thinking maybe seomthing was wrong with the LED I proceeded to try two more XP-Gs with the same results.

    Moving on to some tests with an ammeter I found that with 10440 on high the Nichia would peak at about 700-750mA. The XP-G would start at around 900mA and then climb very quickly up to 1A then 1.1A than 1.2A at which point the pill got to hot to hold.

    Thinking that there may have been an issue with just that driver I swapped the drivers between the Nichia and XP-G. The results were the same which leads to the questions as to why:
    • Why does the light run proper on 10440 with the stock XP-E and Nichia while XP-G produces very high current?
    • Do the 10440 and Nichia have a lower Vf than the XP-G? Could a lower Vf cause that much a dramatic difference in current draw?
    • Is it possible that to produce the Vf and current to draw the XP-G on high the LF2XT driver just couldn't push the required total power?
    • I have read a few threads of what claim to be successful XP-G mods to LF2XTs, have any of these mod owners experienced a similar issue? Or, have they even run the lights on 10440 at these levels to test them out?

    Thanks in advance for any helpful thoughts.

  2. #2
    Flashaholic* stoli67's Avatar
    Join Date
    Jul 2010
    Sydney Austalia

    Default Re: LF2XT Mod Issues - Lots of HEAT

    I have an XPG in one of my TI LF2XTs..... does not get too hot.... certainly not in 10 sec! Ihave not measured the current draw though.

  3. #3
    Join Date
    Dec 2008
    Sydney, Australia

    Default Re: LF2XT Mod Issues - Lots of HEAT

    Quote Originally Posted by ShineOnYouCrazyDiamond View Post
    • Do the 10440 and Nichia have a lower Vf than the XP-G? Could a lower Vf cause that much a dramatic difference in current draw?

    I presume that would be asking if the XP-G has a lower Vf than the 219? When going into direct drive an LED with a lower Vf will draw a higher current than one with a higher Vf. The datasheet says a typical XP-G has a Vf of 2.9 V at 350 mA, and looking at the current vs Vf graph, offsetting it by even 0.1 V results in a fairly large change (Vf for 700 mA will now provide ~1000 mA).

    Only way to see for sure if it's the Vf is to run them at a known constant current then measure the voltage drop across them.
    Finning does help dissipate heat. This is why the fins are removed before cooking fish. Otherwise it will throw off the heat and not reach the proper cooking temperature. --Duglite

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