Author Topic: LED battery substitution  (Read 3805 times)

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dnix71

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LED battery substitution
« on: March 06, 2013, 05:01:37 PM »
I have 2 different "Commercial Electric" brand LED battery powered flashlights (aka "torch" to those in the UK). The smaller of the 2 uses 3 AAA alkaline or carbon-zinc cells and has a base which is the same diameter and threads as a common palm torch sold everywhere here for $1.99US under no name. Even the battery holders between the two are interchangeable if you bend the springs a bit.

The palm torch has it's on-off switch in the base and the other, like it's bigger cousin, has a push button on the side.

The largest torch uses two 3.7v lithium cells in a series pack.

Since a AA battery is pretty much the same length as a 3 AAA pack, I tried a AA size 3.2v LiFePO4 cell in a AA battery holder in the two smaller torches and they both work. I clipped off the wires on the AA holder and added a bead on solder top and bottom. It takes a little bit of practice to get the replacement pack seated on the springs but once done the lights work as well from one higher voltage cell as they did from three lower ones.

The smaller light has 9 LED's, the larger has 16. There are versions of the palm torch sold here that have 7, 5 or even only 3 LED's. All the palm torches work for hours on alkaline AAA's, but the 16 LED torch really should have had a bigger battery pack.

A 3.2 LiFePO4 cell is pretty near the safe discharge limit at 3 volts, which is also the minimum voltage needed to light the LED's so if you use a rechargeable cell it shouldn't be ruined if you run the light until it quits. A single LiFePO4 cell is cheaper here than 3 AAA's, so it's an affordable hack.






Simen

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Re: LED battery substitution
« Reply #1 on: March 06, 2013, 10:45:17 PM »
LiFePo4 cells has a discharge limit at 2.5V, and a charge limit at 3.65V. (As opposed to 3.00V/4.20V for most other Lithium based rechargeable cells.) ;)
I will accept the rules that you feel necessary to your freedom. I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. - (R. A. Heinlein)

Harold in CR

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Re: LED battery substitution
« Reply #2 on: March 07, 2013, 06:52:14 AM »

 My Son sent down 3 Home Depot special single LED lights. They are unbranded, 5 inches long and have the end switch.

 I took out the triple battery holder and took 1 laptop lipo battery, cut a piece of PVC pipe and split it down the side, and slipped it over the lipo cell. I then took a freshly charged lipo cell, and did a discharge, bleeding off that 4.15 v, down to 3.9.

 Doesn't take much and, the LED seems fine. At night, this light can illuminate things over 100 yards away, no problem.  The end switches are junk, so, I need to figure out a switch. IF I tighten the end too far, the switch doesn't function, so, I back it off until it works OK, then run a couple wraps of vinyl tape around the joint.

RandomJoe

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Re: LED battery substitution
« Reply #3 on: March 08, 2013, 05:25:42 AM »
Very cool.  I have quite a few of those little "unbranded"-style LED flashlights, will have to go get some AA LiFePO4s.  Never even thought about that...  (The only LiFePO4s I have so far are A123 packs, so a bit large...)

I've wondered what's up with the switch on the end of these flashlights too.  Seems remarkable they'd make what's otherwise a very nicely machined item only to use such a ridiculously flimsy switch.  Every single one of mine has gone bad.

I also have a light like the large one, actually had a second a while back that I gutted.  Both used six AA NiMHs in a soldered-together pack, wonderful lights while they worked but the batteries were awful.  Died in a hurry.  Had to do surgery to get the base opened, they were WELL glued, but might be able to put the second back together with a new cell type inside.

I don't know whether to be disappointed or happy - so disappointing to see otherwise-useful kit basically destined for trash/recycle because of short-sighted design decisions, on the other hand long as I can intercept the stuff I do get lots of nice goodies to tinker with free of charge! :)

RandomJoe

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Re: LED battery substitution
« Reply #4 on: March 08, 2013, 06:18:31 PM »
That's quite impressive...  Went by Home Depot and got some Hampton Bay-branded cells, two for $13, rated 1AH.  Out of the pack they measure 3.45V, and work a treat with the small LED flashlights.  What really surprised me was that I can't tell the difference between the LiFePO4 at 3.45V and the AAA pack at (unloaded) 4.27V. 

Fluke meter says they are drawing 60mA with the LiFePO4, and 120mA with the AAAs.  There are 9 LEDs in parallel so I was expecting closer to 180mA, and would have thought they'd be noticeably dimmer at only 60mA.  The LEDs ought to last forever at this rate! :)

Now I just need to fashion some sort of 2-cell holder to try them in the larger LED light, and a holder / jig for the charger.  I have a Cellpro Multi4 which should charge these just fine - has a preset all ready for them - I just need to connect to the charging harness.

I am curious about battery sizes though.  Reading the OP, and some other posts I found online, I got the impression an "AA-sized LiFePO4" was actually the size of an AA - would even fit in an AA holder.  The ones I got are in fact the same *height* as an AA, but are noticeably fatter than even my highest-capacity NiMH cells, which are already quite a tight squeeze in an AA holder.  Are there several sizes of these things running around?

dnix71

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Re: LED battery substitution
« Reply #5 on: March 08, 2013, 06:31:55 PM »
RandomJoe The AA sized LiFePO4 cells I have are exactly the same dimensions as a common AA battery. They are made that size on purpose. Because they have exactly double the nominal voltage as an alkaline AA they can be used with a dummy cell where 2 AA's would be. I bought them for my camera. The pictures I post here were shot on a Canon 120IS using one AA sized LiFePO4 cell and a homemade dummy cell.

RandomJoe

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Re: LED battery substitution
« Reply #6 on: March 08, 2013, 06:45:13 PM »
Okay, good to know.  I'll look around a bit more.  The ones I got are intended for landscape lighting.  I now remember reading about your camera post, that would be handy.

The thicker cell is actually helpful for these little flashlights I have, it's slightly narrower than the original cell holder so rattles around a bit inside but makes contact just fine.  A few turns of electrical tape around the center of the cell shimmed it nicely in the center of the flashlight body.

dnix71

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Re: LED battery substitution
« Reply #7 on: March 08, 2013, 07:18:23 PM »
This is an example from eBay. Radio Shack also sells them as solar landscape replacement cells. Note the voltage as 3.2, these are lithium iron phosphate, not the 3.7v organic lithium.

THESE http://www.ebay.com/itm/2-14500-3-2V-600mAh-LiFePO4-AA-Size-Rechargeabe-Battery-1pc-2pcs-1-2-1-5V-Cell-/321045237949?pt=US_Rechargeable_Batteries&hash=item4abfc990bd

or https://www.radioshack.com/product/index.jsp?productId=4230401

NOT these from Radio Shack, they are 4/5's of a AA https://www.radioshack.com/product/index.jsp?productId=12905984

Simen

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Re: LED battery substitution
« Reply #8 on: March 08, 2013, 11:29:17 PM »
Dnix;
Please, do not call the non-FePO4 cells for 'Organic' Lithium; they're mainly Cobalt or Manganese based, and there's nothing organic about them. Let's not start 'mis-naming' Lithium cells; it will only lead to confusion later on. :)

That said; there are some research on using Purpurin instead of Cobalt in Lithium cells; an organic compound derived from a plant called Madder, but this is still experimental... ;)
I will accept the rules that you feel necessary to your freedom. I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. - (R. A. Heinlein)

dnix71

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Re: LED battery substitution
« Reply #9 on: March 09, 2013, 11:48:14 AM »
Simen Okay.

The original separators in high powered Li cells were acetates. If the cell was overcharged or overheated the separator would melt, the electrolyte mix and then hydrogen gas produced in the cell would burn along with the acetate separator. Only the LiFePO4 cells don't produce hydrogen gas so they didn't burn if overcharged.

The inherent safety of LiFePO4 cells is why I prefer them over the others with slightly higher voltages.

Simen

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Re: LED battery substitution
« Reply #10 on: March 09, 2013, 03:17:43 PM »
I'll agree on that point. ;)

Fyi;
Cobalt based cells has a thermal runaway at around 150deg. C., Manganese, 250C, and FePO4 ones, around 270C. :)

The cobalt ones are now better than they were in the beginning, but still not the safest. (I'm sure that's what the Dreamliners use... ;D ) Common to all of them nowadays, are internal pressure vents and temp fuses.

But they'll all get very hot if shorted/overloaded, and could ignite other stuff around it, so care should always be taken...

'nuff lecture; have fun... ;)
I will accept the rules that you feel necessary to your freedom. I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. - (R. A. Heinlein)

Crispy

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Re: LED battery substitution
« Reply #11 on: March 10, 2013, 06:21:54 AM »
I have no real knowledge about these batteries but thought I'd share this if it could be of use.

I just ordered a device that helps to quit smoking. It produces a vapor with nicotine in it. The batterys come in 2 sizes and are Lithium ion with a voltage range from 4.2v fully charged to 3.2v at discharged. Capacities are 1500 mAh and 2800 mAh.

With all the references to safety issues in some of the posts I thought it would be of help to mention these as they are what's called "protected" batteries where internal circuitry built in will shut them down if they overheat.

If anybody is interested, I can report back later this week when they arrive with actual dimensions and pictures of the ends. This may be old news to many of you who play around with this stuff a lot but thought I'd share anyway.

Here's a link and since I'm past the 50 post threshold I should be safe doing this. Guaranteed NO SPAM  :D

https://www.vapor4life.com/omgad-18650

My hair is smoldering for a reason, that's why I'm here.

Simen

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Re: LED battery substitution
« Reply #12 on: March 10, 2013, 12:43:30 PM »
Yup, i use the same kind of cells in my e-cigs... ;) Those are also the ones common in laptop battery packs.

As the number on the cell indicates, they're 18x65mm. ;)
I will accept the rules that you feel necessary to your freedom. I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. - (R. A. Heinlein)

mulan

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Re: LED battery substitution
« Reply #13 on: April 20, 2014, 08:03:02 PM »
How do you get the base off the big one to try and replace the battery pack? Is it glued? Press fit? Any tricks to getting it apart?

MaryAlana

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Re: LED battery substitution
« Reply #14 on: April 21, 2014, 01:19:32 AM »
Quick and dirty dummy cell is a piece of dowel the right diameter cut to length and wrapped with aluminum foil.