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Thread: Rechargeable Lithium

  1. #1

    Default Rechargeable Lithium

    Green laser pointer rated 200 mW. That is the laser beam output, the pumping infrared diode uses about 1 watt. Uses 2 AAA batteries. Problem is that it quickly drains the batteries, the batteries are dead after 3-4 minutes of use. To save money, rechargeable batteries are typically used. The problem is that common NiH batteries are rated 1.2 V, unlike the normal 1.5 V in normal batteries. Since the laser is designed to run on 3 V, but is only getting 2.4 V, there is a very noticeable drop in light output. It seems like the light output is reduced by 40-50 percent. The laser uses an infrared emitting diode, and just as with LEDs, a fairly small drop in voltage will greatly reduce the light output.

    Rechargeable lithium batteries exist. I thought I saw 1.5 V AAA rechargeable lithium batteries somewhere online. They were rather expensive, and required their own special charger specifically designed for lithium batteries. Apparently a standard battery charger cannot be used because of fire danger, because it will overcharge the lithium batteries. 2 batteries and the charger were 35 dollars if I remember correctly. I cannot find the link now, this was over a year ago.

    I clearly remember seeing them for sale somewhere online. I am absolutely sure they were rechargeable and not 3.7 volts... or maybe it was a single 3.2 volt battery and I am not remember correctly? Here's a 2-segmented 3 volt rechargeable lithium, presumably each cell is 1.5 volts:
    http://www.bhphotovideo.com/bnh/cont...G&Q=&A=details

    The laser can operate with 3 NiH rechargeable batteries (3.6 V total). The beam is brighter, but I did not feel comfortable running it for more than a few seconds. Being a cheap chinese import, the diode is probably already overdriven, and the instructions said not to leave it on for more than a minute continuously. Something about overheating, it did get noticeably warm. Also the housing is not designed for 3 batteries, so it is rather annoying to have to precariously hold it in place.

    This whole thing seems like a terrible design. They could have at least designed the housing to be thicker to use AA batteries.

    I just wanted to mention this because maybe there are other people out there facing the same problem, or who are using rechargeable batteries and wondering why their laser is not putting out as much light.

    Does anyone else have more information about standard shaped rechargeable lithium batteries, and where to buy them? They seem to be quite difficult to find and very expensive.

    There are also NiZn rechargeable batteries rated at 1.6 V each.
    Last edited by Anders Hoveland; 04-11-2013 at 10:34 PM.

  2. #2
    Flashaholic* oKtosiTe's Avatar
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    Default Re: Rechargeable Lithium

    My guess is that those two cells are used in parallel, not in series, hence both cells operate at 3 volts.

  3. #3
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    Default Re: Rechargeable Lithium

    Hello Anders,

    To clarify the difference between the voltage ratings of primary and secondary cells keep in mind that an Alkaline AAA cell is rated 1.5 volts OPEN CIRCUIT where the NiMh AAA cell is rated 1.2 volts UNDER LOAD. It is strange that you see better performance with the Alkaline cells. Usually the internal resistance of the Alkaline cells is much higher than that of NiMh cells and this leads to reduced voltage under heavy loads.

    Alkaline cells are 1.5 - 1.6 volts open circuit.
    NiMh cells are 1.4 volts open circuit off the charger and 1.2 volts under load.
    Early Li-Ion cells were 4.1 volts open circuit and 3.6 volts under load
    Current Li-Ion cells and Li-Po cells are 4.2 volts open circuit and 3.7 volts under load.
    In addition there are a few brand new Li-Ion cells that have an open circuit voltage of 4.3+ volts.

    On the other hand your AAA NiMh cells may be crap.

    I don't know what cells they are using for the camera battery pack, but I had a GPS unit that offered a Li-Ion replacement pack. I went through several because the quality of the cells used were not very good. When I dismantled one of them I found that they were using a 10440 cell with a diode to reduce the voltage.

    If you want to try some quality AAA NiMh cells, look for some Eneloop AAA cells.

    If you want to stick with primary cells, Energizer makes some AAA lithium primary cells that work very well.

    Another option would be to pick up a single 10440 Li-Ion cell (and a charger to charge it) and use it along with a spacer in your laser. Before going this route you may be able to find some discharge graphs on the 10440 cell and that would give you an idea of the voltage it would be capable of under load.

    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
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    Default Re: Rechargeable Lithium

    Here you go: http://www.ebay.com/itm/2-pcs-1-5v-1...item3a8451ebf1

    Super pricy, but just what you were looking for.
    >

  5. #5

    Default Re: Rechargeable Lithium

    Those cells remind me of the old Tadiran TLR "InCharge". 3.0V Li/MnO2 (as in metallic lithium, like CR123A) but (get this) rechargeable. Was a competitor to early and low-capacity/high-IR Li-ion cells. There was only ever one cell, a 15500 size (fat AA). Apparently they were very safe and rather tough, and when pushed they tended to just die in a benign manner rather than going boom. Back in the 90s and early 2000s, there was some RC use of surplus cells for small electric aircraft and some hobby chargers that could charge them, and since then everything about these strange cells and their use has completely vanished. Anyone heard of 'em or have any?

    On topic, for one thing alkies will not hold 1.5 under load as mentioned. They are closer to 1.2 at light loads, so the dimming makes no sense unless your nimh cells are just garbage with no current capability. 1 watt at 2.4V is 417 mA which is a fairly large load for AAA alkaline hence the minutes of runtime. Good NiMH cells (not Chinese offbrands, but reputable consumer brands or Sanyo/Eneloop, Kan, Elite, GP, etc.) should have at least 1.5 hours of runtime on a charged set of 2 cells. Just be careful with what sounds like a direct drive diode not to blow it up. A lot of sketchy LED/diode devices are direct drive, not even a resistor and rely on the alkaline cells to limit current, putting low-resistance cells in them = .

    Also, Li-ions generally have a steeper discharge curve than the equivalent 3 nimh cells and the first part of that has a voltage close to 4 volts under load. I wouldn't chance either the diode or the 10440 with what might be a dangerous current.

    Edit: Apologies for replying to a necro.
    Last edited by torukmakto4; 09-13-2013 at 02:55 PM.

  6. #6
    Flashaholic* bshanahan14rulz's Avatar
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    Default Re: Rechargeable Lithium

    I use a single, protected 10440 in my cheapo 30mW green pointer. Made a spacer out of a length of PC power cable, with self tapping screws on each end. Ain't burned out yet, but if you are worried about it, throw one or two rectifiers in-line inside the spacer to drop the extra voltage.

    Now, for a 0.2W pen, well, that sounds goofy to begin with, so it's up to you. Let it be known that I bought my green pen for $10, so no biggie if after several years now, it dies.

    edit: just noticed this thread is 5 months old. Meh.

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    Flashaholic* Rosoku Chikara's Avatar
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    Default Re: Rechargeable Lithium

    Quote Originally Posted by android View Post
    Here you go: http://www.ebay.com/itm/2-pcs-1-5v-1...item3a8451ebf1

    Super pricy, but just what you were looking for.
    Well, I took a look at the cells in the above link, and they sure seem weird to me. I have no plans to rush out and buy any, but they have left me curious.

    Can anyone explain what is going on? How are they likely made? What is their likely chemistry? What are the benefits (if any)?

    Here are some other pictures I found. The Chinese characters in the center of the "Logo" in the first photo read "Double Pressure" (meaning Dual voltage). The second photo was originally annotated in Chinese, and I translated the parts that were clear into English. But, the "Insulation Enclosure" (or Insulation Circle or Pen) remains mysterious to me. Is that where they are "stepping down" from 3.7v to 1.5v?



    Sorry, I do not understand electronics or even electricty all that well. Does the process of "stepping down" to 1.5v provide some benefit in terms of capacity, despite what I suspect would be considerable inefficiency?

    Their claim of 1100 mWh (for AAA size) translates into about 300 mAh for 3.7v and 700 mAh for 1.5v, according to my inexperienced calculations. Both of these numbers seem realistic enough, but seem to offer no benefit in capacity. So, these batteries are "good" simply because they can really deliver constant 1.5v? No other benefit? (If so, seems like a lot of work to go to for a small niche market, and it would seem that the price would deter most potential buyers.)

    I really have no pressing need for these answers, but I am curious. If someone has the time to explain things to me, I would appreciate it.
    Last edited by Rosoku Chikara; 09-13-2013 at 06:47 PM.
    My avatar photo is that of a small handmade toy boat that propels itself along the water in a realistic "chug-chug" kind of motion, yet is powered entirely by CandlePower. (Japanese children used to make them out of various types of junk, but now they are largely a "lost art.")

  8. #8

    Default Re: Rechargeable Lithium

    Sometimes they want a certain diameter, and pick an appropriate cell to use as a standard sleeve/cell size.

    They then put a teeny cheap cell inside to provide the actual power.

  9. #9

    Default Re: Rechargeable Lithium

    Well that explains a lot.

    Clearly a regular old Li-ion cell with an added regulator of some kind to get 1.5V. I am guessing it is a switching regulator since the claim is in mWh, and 300mAh at 3.7V linearly regulated to 1.5V is still 300mAh.

    I guess the intent here is to make a rechargeable battery that produces 1.5V in order to get some voltage-specific devices (which wouldn't like NiMH) to operate.

    I wonder about the converter... current limit? Does it have low voltage protection for the Li-ion cell? I would assume it does, and the price reflects the converter.

  10. #10
    Flashaholic* Rosoku Chikara's Avatar
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    Default Re: Rechargeable Lithium

    Quote Originally Posted by torukmakto4 View Post
    Well that explains a lot.

    Clearly a regular old Li-ion cell with an added regulator of some kind to get 1.5V. I am guessing it is a switching regulator since the claim is in mWh, and 300mAh at 3.7V linearly regulated to 1.5V is still 300mAh.

    I guess the intent here is to make a rechargeable battery that produces 1.5V in order to get some voltage-specific devices (which wouldn't like NiMH) to operate.

    I wonder about the converter... current limit? Does it have low voltage protection for the Li-ion cell? I would assume it does, and the price reflects the converter.
    Thanks for the explanation. Seems like a pretty expensive solution to those relatively few devices that "don't like NiMH." It wonder if these batteries will ever really sell.
    My avatar photo is that of a small handmade toy boat that propels itself along the water in a realistic "chug-chug" kind of motion, yet is powered entirely by CandlePower. (Japanese children used to make them out of various types of junk, but now they are largely a "lost art.")

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