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    LED batteries and set up

    I wonder if someone would be kind enough to help me? I have recently decided to fit a LED single bulb into my products. But im having a few problems, and i dont want to guess, beings that it involves customers. [which i respect]

    My requirements is for the LED battery[ies] to last approximately 12 months[?] before changing. And i assume the the actual bulb can last 10yrs+.

    Could anyone suggest what type of battery[ies], or 'set up' i would need to achieve this?

    Thanks in advance for any replies [and i hope that its not off topic - if so my sincere apologies]

    kind regards Vince

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    Re: LED batteries and set up

    With a 5mm LED that consumes 10mA a good quality car battery will last about 140 days.


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    Re: LED batteries and set up

    Quote Originally Posted by Vbase View Post
    With a 5mm LED that consumes 10mA a good quality car battery will last about 140 days.
    Thanks for your reply Vbase. Sorry i should have mentioned a usage of 1.400 hrs [approx]. before changing the batteries.

    Am i 'barking up the wrong tree', and needing something far larger than 'coin' or 'AAA' batteries? ... [can i do this without 'transformers' or any external wiring?].

    Many thanks
    Vince



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    Re: LED batteries and set up

    There are tiny fairly dim LEDs and there are big very bright LEDs. The tiny dim LED uses low current and the big bright one uses lots of current.
    But you did not say what the LED will do. Is it simply an indicator that can be fairly dim or is it for brightly lighting a room or yard at night?

    Name-Brand disposable batteries last for 10 years if you do not use them. They last for a couple of seconds if you overload them.
    We do not calculate if a battery will last one year, instead we calculate the total time during one year that the battery will be powering the LED then select a battery that is big enough to do it.
    But you forgot to say the total time the battery will power the LED during one year.

    If you use a circuit to briefly blink the LED a couple times per second then it is turned off for most of the time but is still fairly bright and its battery can be much smaller or last much longer than if the LED was turned on continuously.
    As the battery runs down then the LED brightness also runs down unless you use a circuit to keep the current constant.


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    •   Alt16th April 2015, 23:43

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    Re: LED batteries and set up

    High capacity batteries will be useful, but can you use them? How much available space do you have? You might get the energy from other sources than the battery, for example, solar light during the day. If you can achieve that then you could reduce the battery capacity (and size too).


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    Re: LED batteries and set up

    Hi,

    Vincent Tubb

    The mathematics is not difficult.

    If LED current is 10mA (i don´t know) and you you draw this current from a battery over 1400 hours, then

    10mA x 1400h = 14000mAh = 14 Ah.

    ********
    if you use a kind of DC/DC converter to step down battery voltage to LED voltage, then the battery current is less than the LED current. (otherwise it´s useless )
    then use the battery current for battery capacity calculation.

    Mind that batteries (especially lead car batteries) have self discharge.
    Battery manufacturers have datasheets of their batteries. Read them.

    Klaus


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    •   Alt17th April 2015, 07:45

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    Re: LED batteries and set up

    The datasheet of a Name Brand CR1632 coin cell battery shows that it cannot produce enough current to light a little LED brightly but can dimly light a little red LED for about 12 hours.
    If you use two Name Brand AAA alkaline cells in series then they can light a little LED fairly brightly for 50 hours or dimly for about 120 hours.
    If you use two Name Brand D alkaline cells in series then they can light a little LED fairly brightly for about 800 hours.


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    Re: LED batteries and set up

    Thank you for the replies, your very kind.

    The item i intend to fit it into, is a cast polyester pyramid. [shown in my website http://www.orgoneuk.com/] I intend to drill out a hole from the bottom, to the base of the crystals, and insert the bulb, thus illuminating the crystals.

    My only specifications is to keep the battery[s] as small as possible, [which i will fit to the base]. And for the customer not to be changing the battery[s] every month. I think the minimum of 3 months would suffice, equaling approximately 110 hours.

    I intend to have a 'on/off' switch. And i think the bulb brightness should be a medium 'brightness' bulb [?] .... *The pyramid has s 6" base, with a 5" height.

    If someone could tell me exactly what i would need, it would be greatly appreciated.

    Thanks again, Vince .. [PS im sorry about not uploading a picture, but it was telling me 'bad email address']



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    Re: LED batteries and set up

    110 hours at 20mA is 2200mAh. You need two Name Brand AA alkaline cells to light a little red LED or 3 or 4 AA cells for white, blue or bright green. The LED will gradually dim during the 110 hours. It will probably not be visible after 110 hours.
    Most LEDs have a very narrow beam of light but some produce wide angle light that you need.
    A series current-limiting resistor is needed.


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    •   Alt17th April 2015, 19:50

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    Re: LED batteries and set up

    I think any expectations for bright, long hours of storage and fit into a small space are not realistic.

    Even the smallest I would consider is too big for your application and too short a runtime.

    A CR-123A Primary Lithium 3.0V directly across 20mA = 60mW approx with compatible white LED with only 65h expected life.

    using $0.90 3.9Wh cell yields 65 h runtime.

    60mW would only radiate ~ 6 lumens from a great choice LED +/-50% and would be attenuated from your plastic transmission losses by 99% and thus end up being at best a gentle glow in the dark.

    I have tried not quite similar clear crystal pyramids or photo laser etched monoliths and found I needed at least 10W to compete with ambient twilight.

    can you get away with tiny magnet wire and remote power for just a base?

    how many do you need?
    A good design question lists your overall requirements™ The best question deserves a better answer. ™
    ... Tony Stewart EE since 1975


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    Re: LED batteries and set up

    So i would take it that i have two choices then[?] ... #1 - having 3-4 AA batteries for a 110hr runtime ... OR ... #2 - using coin batteries for a 65hr runtime ... Given that choice, i'd be forced to go with the AA batteries.

    In reply [SunnySkyguy]. So you have tried [almost] the same thing then? ... In regards to the lumens, i am with not concerned with using it as a lamp, but *only to illuminate the 'crystals'. I have done a test on one of my pyramids, using parts i got from a novelty 'LED torch cigarette lighter', and i did have good results. But as discussed, it probably wouldn't last too long.

    Regarding "can you get away with tiny magnet wire and remote power for just a base?"... Unfortunately i really dont want to do any kind of plug-in devices ... Hmm ... And just to answer your other question [SunnySkyguy] .. "how many would i want?". I would need at least 50 [having tested one]

    ... Again, many thanks for the replies. Much appreciated! Thank you!



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    Re: LED batteries and set up

    CR-123A Primary Lithium 3.0V is not a coin cell. It is more the size of 2/3 one AA battery with 3.9Wh. capacity but perfectly matched to LED voltage for white with slightly more capacity than the best AA Alkaline battery at 1 to 1.7V

    It also has a more fixed voltage during discharge, hence more constant current discharge and brightness than Alkaline.
    The battery voltage of Alkaline will drop 10% then >33% to get most of its life, while Lithium stays at 3.0V for most of its life.

    See here $0.90

    These are Li-MnO2 cells at 3.0VLi-FeS2 Lithium batteries are 1.5V

    You can also get Lithium primary in AA size with 1.50 V and 5.1Wh or two such AA's with 3.0V and 10.2Wh. But these are much more expensive.
    A good design question lists your overall requirements™ The best question deserves a better answer. ™
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    Re: LED batteries and set up

    Many Thx 'SunnySkyguy' ..... I think i may now be ready to buy the materials ... Would there be any chance of informing me of the 'run time', and resisters needed, with these two types of batteries :

    #1 - Li-MnO2 [3v]
    #2 - Li-FeS2 [1.5]

    [i will be using a 5mm white, and blue LED bulb]

    Again many thx SunnySkyguy ... much appreciated!
    Kind regards Vince



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    Re: LED batteries and set up

    Since White LED is actually a Blue LED substrate, both have the same threshold voltage of around 2.85V at <10% of rated current and both 3.0-3.2 at rated current depending on chip size. Batteries will drop V with rising current according size too but these types are best for low effective series resistance.

    Thus you need a cheap $10 DMM to verify your choices of both measuring current and voltage. With good match in each, no resistor is needed at 3V. 5mm LEDs will look like 2.85V loads with 15-20Ω series R inside thus are spec'd at 20mA with 3.0-3.2V typ.. If current is too high for your expected discharge lifetime , add 5 to 10 Ohms. If current is too low (dim) then poor choice of LED . A good LED will be >10,000 mcd at 30deg or >20.000 mcd at 15 deg. A great one will be be 60% more. A poor one < 1000 mcd at 30 deg.

    If the beam is too sharp, sand the lens tip to dull/diffuse it. But sharp angle may look better in the right position. You can solder with AWG 30 magnet wire to LEDs, but not to batteries. This needs a tinned spring loaded contacts. Most coated wire can be burned off with solder but 5mm LED can handle 3 seconds only to cathode, never >5.

    there is more to this than meets the eye.
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    Re: LED batteries and set up

    A white or blue LED needs about 3.0V to 3.8V so the batteries probably WILL NOT WORK, especially since their 1.5V or 3V will drop as they are used. That is why I kept mentioning a 1.8V to 2V red LED.
    My projects that use blue LEDs are powered from four AA alkaline cells in series that make 6.4V when new and the blue LEDs are still visible when the voltage has dropped to 4.0V. My Chinese flashlight with 24 white LEDs is powered by three AAA alkaline cells that do not last long and I can see the light dimming as the voltage runs down. I am timing it right now powered by cheap Ni-MH AAA rechargeable cells.

    Will each pyramid use TWO LEDs? A white one plus a blue one? Then the current is doubled and the running time is halved unless each LED is dimmed.


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    Re: LED batteries and set up

    @Vincent Tubb:

    Japs still have not designed the petrol tank of 2x2x2 cm that holds 20 l of fuel
    Japs still have not designed coin sized battery of 100 Ah capacity.

    Next:
    - Nickoli Tesla should be Nikola Tesla
    and
    - place a button on your web site to turn the music off,please
    Make no mistake between my personality and my attitude.
    My personality is who I am.
    My attitude depends on who you are.


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    Re: LED batteries and set up

    Audioguru, if you use your assumptions on battery chemistry and LED experience. You are correct, it wont work everytime.

    If you follow me with the correct choice of HB white and Blue LED's , it will work, since Vth is <=2.85 and these primary Lithium batteries stay at 3.0 for most of their useful life.
    A good design question lists your overall requirements™ The best question deserves a better answer. ™
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    Re: LED batteries and set up

    All my white LEDs are from cheap Chinese solar garden lights and my blue LEDs are from Agilent (formerly Hewlett Packard but they have another new name now) and are over 3.0V when fairly bright with 10mA or more.
    I have never seen a CR123A battery but Varta and Energizer rate its capacity when its voltage has dropped to 2.0V which will not light a white or blue LED.
    Energizer's datasheet shows its voltage is less than 3.0V when it new with a 28.5mA load so it will also not light my white and blue LEDs even when it is brand new.


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    Re: LED batteries and set up

    Quote Originally Posted by Audioguru View Post
    All my white LEDs are from cheap Chinese solar garden lights and my blue LEDs are from Agilent (formerly Hewlett Packard but they have another new name now) and are over 3.0V when fairly bright with 10mA or more.
    I have never seen a CR123A battery but Varta and Energizer rate its capacity when its voltage has dropped to 2.0V which will not light a white or blue LED.
    Energizer's datasheet shows its voltage is less than 3.0V when it new with a 28.5mA load so it will also not light my white and blue LEDs even when it is brand new.
    You should state your assumptions then, worst case cheap garden LEDs are not recommended but may work.
    (A white or blue LED needs about 3.0V to 3.8V so the batteries probably WILL NOT WORK,)
    White or Blue high bright (HB) LEDs have a threshold is near 2.5 but ESR linear asymptote is around 2.85 and actual Vf forward voltage depends on W capacity * ESR of LED {[ W*Ω ~1 ]}, which you ought to know from my many blogs in the past.


    I found an old (dated 0509A) "123" type Energizer Lithium Photo 03-2019 cell that with a random LED I kept since 2004 resulted in 3.01V @ 8mA. rated for >10Cd @30deg @ 20mA

    Choice of battery and LED require skill and experience I outlined. Both high efficacy LEDs and the chemistry of Lithium I mentioned are very stable and tight tolerance at low LEDs current. Often within a few mV at threshold, so the current is predictable.

    The key is these Lithium battery types have much lower ESR than the LEDs at this current, so there is minimal voltage drop from 3V. As you know the termination voltage is often rated for 0.1C or higher and not <0.01C like this application. The lower the current drain the higher the EoC voltage which may be around 2.85 V where these LEDs grow dim. So in essence not regulated but lit dimly for the life of the battery. Any regulation may drop efficiency or life time a lot from the power lost in the series resistor.

    As I predicted below;




    The CR123A battery was lying around in the drawer for a long time unused and Mfr dated 0509A and I have probably shipped over 1m white LEDs that would all work in the method using less than rated current for small size parts with over 10Cd or >10,000 mcd. ( although I have some 3x that in 5mm)

    added** Cheap AA Alkaline pair wont work very long and need maybe 5 ~20 Ohms in series which affects lifetime.and brightness.. perhaps 1~3 days.
    A good design question lists your overall requirements™ The best question deserves a better answer. ™
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    Re: LED batteries and set up

    SunnySkyGuy, you have some very bright fairly wide angle white LEDs but you say you also have some that are 5mm. Then what size are the white LEDs in your photos? 10mm?


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    •   Alt21st April 2015, 00:11

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