Lithium 3v batteries and holders (coin cells)

MatthewMatthew Posts: 200
edited 2005-01-31 - 22:20:37 in General Discussion
Has anyone ever tried using three of these to power a stamp? I'm using the stamp where weight is a huge factor, and I was wondering if these small cells would do the trick.

Has anyone seen a 3 cell holder for them?

Thanks,
Matthew

Comments

  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-01-30 - 22:33:16
    3 cells? 2, 3V lithiums is 6V. With a ldo regulator, thats enough to power a 5V project. How much life you get out of them depends on the type of stamp (mainly its clock speed), how many outputs your driving, what other external parts your powering and the specific battery. There are dual lithium holders but I've never seen a triple (except in a jerry-rigged holder for hearing aid type (1.5V)).
  • JonbJonb Posts: 146
    edited 2005-01-31 - 03:50:47
    The capacity of these coin cells is quite small. They are mostly suited to memory backup and extremely low power applications.
    Also most of those coin cells cannot be recharged.

    If you want small size and high power look into lithium polymer.

    Post Edited (Jonb) : 1/31/2005 3:54:28 AM GMT
  • BeanBean Posts: 8,117
    edited 2005-01-31 - 12:49:05
    I don't know how small you need, but look into AAAA batteries (that's right quad "A"). There are 6 of these cells in a 9V battery.
    Bean.
  • GadgetmanGadgetman Posts: 2,436
    edited 2005-01-31 - 14:41:38
    I think a CR2032 (commonly used in PDA's and motherboards for backup is rated at about 80mAH, so it is possible to run a BS2 on it for a while.

    I'm working on a miniature BS1 project where I use a single 3V Lithium cell no more than 7mm wide(about 1/4"). Of course, on that project I've disabled the voltage-reset circuitry to run the PIC and EEPROM at the lower voltage. (Not recommended, but... smile.gif
    Unfortunately, this project is on hiatus at the moment because of other projects.
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-01-31 - 18:06:19
    You want a high density with low weight,·get a surplus cell phone·Li-Ion·battery, heres a 7.5V 1200mAh rechargable: http://www.allelectronics.com/cgi-bin/category.cgi?category=160&item=LBAT-35&type=store

    Heres a 3.7v 1200mAh Li-Ion Prizm cell that is 1.89"x1.35"x0.35", 38g and can handle a 2A discharge rate: http://www.allelectronics.com/cgi-bin/category.cgi?category=160&item=LBAT-43&type=store·they also have a version with solder tabs.

    Or there is the SAFT LS14500 nonrechargable 3.6 Volt, AA Size 2.25Ah, 120mA max discharge rate (meaning 18 hours of life at max discharge)·and weights 16.2g (about half the weight of an alkaline battery: http://www.allelectronics.com/cgi-bin/category.cgi?category=160500&item=LBAT-40&type=store·snip the leads off if you want to put it in a standard AA battery holder. The tech sheet for this battery is here: http://www.blubatterie.com/pdf/LS_LST_14500_SAFT.pdf

    If your set on coin cell, they are non-rechargable, CR2032 can have up to 180mAh, CR2025 is 150mAh, CR2450 is 560mAh, but these figures are somewhat a misnomer, because there are·a variety of Li technologies each with its own power density (mAh that will fit in a package) and thier own max discharge rate, heres a page doing a cross section between (CF)n/LI: Poly-Carbon Monofluoride and Mn02/LI:Manganese Dioxide for standard coin cell sizes (there are other Li combos as well): http://www.panasonic.com/industrial/battery/oem/chem/lith/coin1.htm

    Heres how to decipher a CR#### cell's meaning CR(AA)(BB) the AA number is the cell's diameter in mm rounded down to the nearest mm, the BB number is the cells thickness as B.B mm, so a CR2032 is 20 mm wide and 3.2mm thick. So if you got a coin holder for a CR2025, you could stack 2 CR2012's in it, you double the voltage to 6V but you halve the density (mAh).

    Hope this clarifies some of you questions.

    Paul
  • GadgetmanGadgetman Posts: 2,436
    edited 2005-01-31 - 21:10:24
    Paul Baker said...

    Or there is the SAFT LS14500 nonrechargable 3.6 Volt, AA Size 2.25Ah, 120mA max discharge rate (meaning 18 hours of life at max discharge) and weights 16.2g (about half the weight of an alkaline battery:

    Those are neat, but a bit expensive...
    I recently bought a few because I needed one for an old Laptop I was restoring.
    (I always buy more than I need just in case I happen upon another machine or project that needs the same component)

    Paul Baker said...
    Heres how to decipher a CR#### cell's meaning CR(AA)(BB) the AA number is the cell's diameter in mm rounded down to the nearest mm, the BB number is the cells thickness as B.B mm, so a CR2032 is 20 mm wide and 3.2mm thick. So if you got a coin holder for a CR2025, you could stack 2 CR2012's in it, you double the voltage to 6V but you halve the density (mAh).

    Why didn't I think of stacking them in the socket?

    You may also want to take a look at the cells used in those annoying little laser-pointers.
    LR44 and AG13 are very common.
    (They're 1.5V so you'll need 4 of them)

    What kind of run-time are you talking about?
    (Minutes, hours or...)
    Are there any other IC's that also needs to be powered?
    And which stamp?

    The BS1 can be modified to run at 3V just by cutting a single track.
    (But the guys at Parallax don't want us to do it as the Stamp will behave 'unpredictably' when the voltage drops too low)
    Incidentally, it draws less current when running at 3V than at 5V.
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-01-31 - 22:20:37
    Yeah the LS14500 are usually quite expensive, but the site i pointed to sell them for $1.75, $1.50 in quantities more than 10. Standard name brand AA alkalines cost that much if you buy them from your local mart.
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