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Thread: The Princeton Tec EOS Diet…

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  1. #1
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    Lightbulb The Princeton Tec EOS Diet…

    I use a Princeton Tec EOS headlamp all the time at work. I usually set it on low and it keeps me from falling into holes and tripping over things. I use a flashlight to see and inspect with, but for general navigation, the EOS works out very well.

    The EOS is regulated and seems to do a good job of sucking Alkaline cells dry. It is advertised to run about 6 hours on a set of 3 AAA cells on high. On low, I believe the advertised run time is something like 60 hours. Not bad for a set of around 900 mAh cells. Many people have been using NiMh cells and have been pleased with their performance as well. I have not tested NiMh AAA cells at 150 mA, but believe that most brands (regardless of what their label says), should come in with similar capacity.

    The EOS weighs 105 grams with the strap and with a full set of Alkaline batteries.

    While the EOS is fairly lightweight, I decided to put mine on a diet.

    I contacted AW and found out that there are Li-Ion cells that are the same size as AAA cells (10440). Their capacity is a bit low at 320 mAh, but if you parallel them you end up with 3 cells at 4.2 volts and 960 mAh. This is pretty much a direct replacement for the 3 AAA Alkaline cells.

    I ordered some cells and put them in. The middle cell has to go backwards and the negative end does not contact the metal strip. A small magnet took care of that problem, and the plastic holder of the light will keep the magnet from slipping around out of place. EDIT: You also have to jumper the contacts at the top and at the bottom. The contacts are in two pieces in both places and you need to connect them together. END EDIT

    My EOS went from 105 grams to 98 grams and now is more comfortable to wear, should have the same run time, will have better cold weather performance, I am no longer concerned with self discharge, and because the batteries are rechargeable, I am still enjoying guilt free illumination…

    Now I am looking for a place to put a “Lithium Powered” sticker.

    I must add that all the standard warnings concerning Li-Ion cells should be adhered to:

    These cells are unprotected, so charge them often. If you run them all the way down you will destroy them.

    You will need a charger than can handle Li-Ion cells and keep in mind that these are 320 mAh cells. The preferred 0.7C charging rate is 22.4 mA. I am charging at 25 mA. You will need some way to hold the batteries for charging. If you charge them in series, you should make provisions to balance them from time to time. If you charge them in parallel, things on the charging side get easier, but how to hold them becomes more of a challenge.

    Don’t charge Li-Ion cells unattended.

    Charge on a fire proof surface.

    Tom

    As a foot note…

    My wife things I am a bit off because I am running around the house with my head lamp on bouncing my head back and forth trying to see how much of a difference 7 grams makes. I have two EOS headlamps, so I don’t have to change batteries all the time.

    I believe there is a noticeable difference, but I also though that my truck had a little more snap to it when I replace the exhaust system and fitted it with Corvette tips…
    Last edited by SilverFox; 12-08-2005 at 03:36 PM.
    Behind every Great man there's always a woman rolling her eyes...

    Most batteries don't die - they are tortured to near death, then murdered...

  2. #2

    Default Re: The Princeton Tec EOS Diet…

    Good post. Thanks for the idea.

    You can also use NiMH which should work okay if you don't mind the self-discharge.

  3. #3
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    Default Re: The Princeton Tec EOS Diet…

    I forgot to add that you have to be careful when replacing the cells. If you don't put them in correctly, you will probably fry the light...

    Tom
    Behind every Great man there's always a woman rolling her eyes...

    Most batteries don't die - they are tortured to near death, then murdered...

  4. #4

    Default Re: The Princeton Tec EOS Diet…

    I like the EOS too and was wondering about this myself. So the trick in converting it to parallel from series is to reverse the middle battery?

    Thanks

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    Default Re: The Princeton Tec EOS Diet…

    Hello Bogus1,

    You've got it...

    At first I was going to call this a mod, but it is actually more of a substitution.

    The only difficult part is to get a connection between the base of the middle cell and the contact. Usually the battery nipple makes that connection, so I improvised a nipple on the base of the Li-Ion cell using a magnet.

    Tom

    EDIT: Please note that this information is not correct. In addition to reversing the middle battery, you also need to join the two piece connectors at both the top and the bottom of the battery compartment.
    Last edited by SilverFox; 12-09-2005 at 05:53 AM.
    Behind every Great man there's always a woman rolling her eyes...

    Most batteries don't die - they are tortured to near death, then murdered...

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    Flashaholic* jar3ds's Avatar
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    Default Re: The Princeton Tec EOS Diet…

    i wonder what 1.5v lithiums would reduce the weight.... ? i think i'll be going more that route

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    Default Re: The Princeton Tec EOS Diet…

    I have run into a problem with this project... EDIT: Problem fixed... END EDIT

    I have been doing some run times and am getting similar results to what Doug (Quickbeam) got. About 2 hours regulated light on high, then things start to dim.

    However, when checking the voltage of the individual cells (total system voltage was around 2.9 volts), I am finding that the two outer cells are pretty close, but the middle cell is over 4.5 volts.

    Everyone knows that is not a safe voltage to be at with Li-Ion chemistry.

    How does a parallel pack charge its center cell under load?

    I am sure there must be a good reason this is happening, but I am at a lost to explain it...

    Tom
    Last edited by SilverFox; 12-08-2005 at 03:37 PM.
    Behind every Great man there's always a woman rolling her eyes...

    Most batteries don't die - they are tortured to near death, then murdered...

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    Default Re: The Princeton Tec EOS Diet…

    just reversing the middle cell can not be the only mod needed to put all the cells in parallell.

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    Default Re: The Princeton Tec EOS Diet…

    to get real light weight, lithium disposable ?
    or does it make no diff?
    if killing was legal, i would have killed countless number of people...

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    Flashaholic* jar3ds's Avatar
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    Default Re: The Princeton Tec EOS Diet…

    well... i'm unsure of the weight of the 10440's... or the AAA lithium primary's

  11. #11
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    Default Re: The Princeton Tec EOS Diet…

    Hello Jared,

    I believe the 10440 cells are close to 6 grams each.

    Tom
    Behind every Great man there's always a woman rolling her eyes...

    Most batteries don't die - they are tortured to near death, then murdered...

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    Flashaholic* jar3ds's Avatar
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    Default Re: The Princeton Tec EOS Diet…

    thanks silverfox.... i'm ordering up some 10440's ...

    how do you charge them? I'll use AW's 10440 charger to get me by for a while... however in the future...

    I'm thinking about buying a 4xAAA holder from http://www.thomas-distributing.com/battery-holders.htm

    then making that holder parallel... then connecting it to my DSD (or some other charger)... I would assume if I hook up 3x10440's in parallel that the charging current of the DSD would be safe... but i'm just guessing...

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    Default Re: The Princeton Tec EOS Diet…

    I get nervous just thinking about unprotected cells going on my nightstand, and your strapping them to your head.
    Great bunch of info here!
    Just one more light and my collection is complete! Ok, maybe two..

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    Default Re: The Princeton Tec EOS Diet…

    Hello Pydpiper,

    Almost all of the problems associated with unprotected cells occur during charging. With this in mind, I simply use a quality charger and check the voltage before charging. If the open circuit resting voltage goes below 3.3 volts, my plan is to stop using the cell and replace it.

    The next source of problems comes from physical abuse. I feel the light offers adequate protection, so no worries there.

    The final thing to keep in mind is that there is not a lot of capacity to deal with. I am guessing that an "event" with a very low capacity cell will not amount to much.

    All in all, I feel confident with this set up and use it freely.

    Tom
    Behind every Great man there's always a woman rolling her eyes...

    Most batteries don't die - they are tortured to near death, then murdered...

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    Flashaholic* jar3ds's Avatar
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    Buttrock Re: The Princeton Tec EOS Diet…



    Thank to Silverfox for this thread and coming up with this idea.

    I got ~ 1 hour and 25mins... so Silverfox's 1hour&15mins is not too far off at all!

    I used an McR-18 reflector that has been cut down and this is by far the best beam I've got'n out of the EOS (cheers to mosport )...

    Also, after the runtime test as soon as it popped out of regulation. I checked the heat. My star was a tad warm and SO WAS THE McR-18! So in addition to having a better beam with the McR-18 (instead of the 17mm IMS)... it aids as another area for heat to travel to... Very nice!

    Also, using the McR-18 I find myself using the medium and low settings a lot more than when I did with my IMS 17mm. Mainly because the McR-18 seems to give me more fill beam between my spot and spill which is really important for a headlamp. So I can expect according to Silverfox, about 4 hours on medium which is quite a bit of light for a decent amount of time, all on a single 10440.

    Since the original topic of this thread was the EOS DIET, I would say that it does lighten up the EOS a lot... it almost feels like there aren't any batties when you use just one 10440 cell. The way I have my EOS wired is so that only a single 1x10440 can be put in (in the bottom slot, perfect for weight distribution when tilted)... however, i did not need to solder anything... I just wedged a small jumper wire into the springs... So at anytime I can take out the jumper wire and go back to using normaling ~1.5v AAA's...

    I will use this mod for my car. I can keep a pack of 10440's in the car w/ me and some lithium primaries. That way I have the slow discharge of LiON's and great cold weather performance, which is very important where I live. However, if I get stranded and need Gas Station replacement batteries all I have to do is take out the jumper wire and I'm good-to-go!

    The EOS is an amazing headlamp. Waterproof to 1 meter, BRIGHT mod'able Lux's, regulated, light-weight, uses the beautiful McR-18 reflector, and has a ton of battery options including li-ions!

    EDIT: well PT's website says 105g for the EOS w/ 3xAlks... So an Alk according to Quickbeams site is 11.5g. That makes the weight w/o batteries 70.5g's... So add 6g for the single 10440 and you have a 76.5g headlamp!
    Last edited by jar3ds; 10-02-2006 at 11:41 AM.

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