MCE and 14.8 volt lithium battery. Driver?- Mtbr.com
Results 1 to 7 of 7
  1. #1
    mtbr member
    Reputation:
    Join Date
    Dec 2008
    Posts
    22

    MCE and 14.8 volt lithium battery. Driver?

    I have a 14.8 volt, 4 amp hour lithium battery and I want to run a MCE led. The parts will all be from cutter, I intend to use their MR11 housing.
    The driver I want to use is the bFlex UIB2.

    The driver specifications say you need 1.1 volts over Vf. That puts it very close to the 14.8 volts of the battery (Vb).
    Has anyone used this combination and does it work? Will the battery voltage drop fairly quickly to below the desired Vf? I expect to be running 700mA, maybe more if I can get away with it.

    Please let me know your real world results, I don't want to order the parts if it's not going to work.

  2. #2

    Reputation:
    Join Date
    Mar 2009
    Posts
    16
    While it's not real world results, 14.8 is 4 * 3.7 (typically called a 4s pack). The lithium ion batteries will drop slightly below 3.7V/cell pretty quickly, but will remain fairly stable throughout the rest of the discharge, reaching around 3.5V at 20% remaining capacity - http://www.buchmann.ca/chap2-page6.asp . Your battery's discharge curve may be different, but most lithium ion batteries have the same sort of characteristic.

  3. #3
    mtbr member
    Reputation: troutie-mtb's Avatar
    Join Date
    Sep 2007
    Posts
    3,062
    Treadly your lithium pack will be 16.8 off the charger and your MCE will most likely be under 13 volts with all dies in series.

    Loads of us on here have used your suggested set up with no problems at all

  4. #4
    aka RossC
    Reputation: ocean breathes salty's Avatar
    Join Date
    Oct 2006
    Posts
    936
    Quote Originally Posted by Treadly
    I have a 14.8 volt, 4 amp hour lithium battery and I want to run a MCE led. The parts will all be from cutter, I intend to use their MR11 housing.
    The driver I want to use is the bFlex UIB2.

    The driver specifications say you need 1.1 volts over Vf. That puts it very close to the 14.8 volts of the battery (Vb).
    Has anyone used this combination and does it work? Will the battery voltage drop fairly quickly to below the desired Vf? I expect to be running 700mA, maybe more if I can get away with it.

    Please let me know your real world results, I don't want to order the parts if it's not going to work.
    I have done it with a 4s MCE but it was using a buckpuck. It allegedly requires 2 V above Vf to stay in regulation but it has worked OK for me so far. My MCE showed approx. 12.3 Vf.

  5. #5
    mtbr member
    Reputation:
    Join Date
    May 2005
    Posts
    3,827
    I had the same concern as well. I decided to build my battery with 5 cells for a nominal 18.5V as seen in this thread

    http://forums.mtbr.com/showthread.php?t=501179

    Cree's spec sheet puts the Vf of the MC-E at 14V. I am sure that many come in less than that but it seems that keeping the battery voltage up will ensure the output stays regulated through the cell's entire range.
    Last edited by Vancbiker; 03-18-2009 at 12:36 AM.

  6. #6
    mtbr member
    Reputation:
    Join Date
    Dec 2008
    Posts
    22
    I blew one of the LEDs on a MCE that I was playing with, after shorting it out I measured exactly 10 volts across three leds whilst running 1000 mA through it.
    So I guess that gives me a Vf of 3.33 volts per LED, with a total of 13.33 for a full MCE.
    Include the 1.1 volts and that takes it to...Ummm ...14.4333 volts.
    That's why I was after real world results.

  7. #7
    mtbr member
    Reputation:
    Join Date
    Sep 2006
    Posts
    251
    And buy another MCE and you get different numbers... Forward voltage changes from led to led.

Members who have read this thread: 0

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2020 VerticalScope Inc. All rights reserved.