Author Topic: Coleman LED lantern - my next victim... ;)  (Read 3907 times)

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RandomJoe

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Coleman LED lantern - my next victim... ;)
« on: June 02, 2013, 11:22:52 AM »
I had some "reward points" on the credit card that needed to be redeemed so searched through the available items for lighting kit.  Most of the stuff they offer is useless to me, but they usually have some nice camping lanterns or other such items.  This time I wound up with a few Coleman LED lights, including this item:



Coleman Quad LED Lantern - uses 8 D-cells, all four panels switch on/off at the same time, VERY bright!  Supposed to run 75 hours on a set of batteries.  Each of the four LED panels also contains 3 AAA NiMH cells, charged from the D cells.  You can detach each panel and use it independently for about 2.5 hrs.  Nice idea, though perhaps rather overkill for my needs...

I've opened it up as best I could, and found it is actually a 6V unit - the D cells are wired in two banks of four.  I can remove either half and the whole unit still works.  Everything wires to a PCB in the top of the unit, under the on/off switch, but that end is apparently sonically-welded.  Looks like the LED panels are also welded shut.

Which brings me to one question I have, anyone know of a better way to try to break sonic welds?  Since it's effectively melting the plastic together I'm assuming not but thought I'd ask.  My usual method - prying with a thin screwdriver - is only going to make a mess of the seam...

I got two, so worst case I can sacrifice one and still have the other intact...!  ;D

I'm curious what all the circuit inside does, whether they really charge the NiMHs intelligently or are doing it dumb/simple, whether they are regulating current to the LEDs or just depending on battery voltage, so on...  Tempted to try some LiFePO4 cells, but that may push the voltage a bit too high depending what's in their circuit...

madlabs

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Re: Coleman LED lantern - my next victim... ;)
« Reply #1 on: June 02, 2013, 12:27:01 PM »

Which brings me to one question I have, anyone know of a better way to try to break sonic welds?  Since it's effectively melting the plastic together I'm assuming not but thought I'd ask.  My usual method - prying with a thin screwdriver - is only going to make a mess of the seam...


A combination of a hacksaw blade and a very sharp knife usually works for me.

Jonathan

hiker

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Re: Coleman LED lantern - my next victim... ;)
« Reply #2 on: June 02, 2013, 01:27:25 PM »
heat up a old thin blade knife-red hot..cuts right throu plastic like butter..
make sure your in a well ventalated area..
WILD in ALASKA

MaryAlana

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Re: Coleman LED lantern - my next victim... ;)
« Reply #3 on: June 02, 2013, 03:11:00 PM »
Dremel with a mini saw blade.

Bruce S

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Re: Coleman LED lantern - my next victim... ;)
« Reply #4 on: June 03, 2013, 09:26:53 AM »
Cheap Dremel knockoff from Harbor Freight with the cutting wheel was great!
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RandomJoe

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Re: Coleman LED lantern - my next victim... ;)
« Reply #5 on: June 16, 2013, 08:29:09 PM »
I finally decapitated the lantern with a dremel - forgot I even had one until it was mentioned here! :)

I'm going to have to do some work, at least a simple voltage regulator, before running this off any 'ol power source - car, LiFePO4 cells, etc.  The circuit board is extremely simple.  Each bank of 4 D-cells connects to a common bus via diode.  The on/off switch simply applies that power to the "power" pin of each of the LED modules.

The "charge" pin was what most interested me, but it's extremely basic too.  Simply another diode from the common bus, then fed to all four LED modules in parallel.  So two diode drops suggests the 3 AAA NiMHs in each module get 6V - 0.7 - 0.7 = 4.6V for charging.

There may, of course, be some more charging circuitry in the LED modules, haven't opened one of them up yet.  I know there's at least a little circuitry, since connecting the module to the lantern causes it to ignore its own power switch and go on/off with the lantern switch.  I made quite a mess of the top of the lantern, am hoping I can find a cleaner way to dissect a module! :)  Perhaps the hot-knife option would be best. 

I've been using the other lantern on kayaking trips.  We occasionally go on late-evening trips where we get back to shore after dark.  The lantern has been great, lighting quite a wide area well.  The detachable modules were a hit too, for the folks who parked farther from me or had to run to the port-o-let!   :D

That was part of my delay in beheading this one.  They work so well as-is, but eventually the desire to know how it ticks overruled...  ;D