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CR-V3 Battery. Possible Steveo-bait

(12 posts)
  • Started 13 years ago by Uberuce
  • Latest reply from steveo
  • This topic is not resolved

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  1. Uberuce
    Member

    As the title suggests, I've got a rechargeable CR-V3 battery leftover from an old digital camera, and since I recall it being splendidly beefy I'd rather see it used. By me.

    Does anyone know off the top of their heads if there's lights that would take one?

    CR-V3's are the ones that are the exact same size and shape as two AA batteries if you'd wrapped them in clingfilm, and have the connections in the same place as if they were nose to tail, so they'll go in a 2xAA space if it's perfectly smooth inside. Digital cameras are made this way for that very reason, but I don't know about bike lights.

    If that's a non-starter, and this is where the steveo part comes in: how would I best go a-bodging?

    Posted 13 years ago #

  2. steveo
    Member

    The fully charge voltage of a pair of AA's is about 2.6v the full charged voltage of the lithium battery is about 4.2v. In a front light there will be witch craft to step the voltage up to about 3.3v that the led needs. In a back light there is usually a small resistor to limit the current plus a circuit to make it flash because red leds work between about 2-2.5v.

    I suspect any "off the shelf" light will release its magic smoke if you put that battery in, its voltage is probably too far out of range for the circuitry.

    However it could be fairly simple to replace the driver and emitters in an existing light.

    Posted 13 years ago #

  3. DaveC
    Member

    Wiki says it may be possible, depending on exactly which battery model you have.

    http://en.wikipedia.org/wiki/CR-V3_battery

    CR-3V 3 volts

    RCR-3V 3.7 volts

    Posted 13 years ago #

  4. Uberuce
    Member

    Ah, I guess digital cameras also have djinns inside to cope with the initial voltage...

    Posted 13 years ago #

  5. steveo
    Member

    Yeah digital cameras will have a converter to keep the voltage at what ever constant voltage they need.

    What you could do is get a 2aa battery holder from maplin and a power led of your favourite colour. I've got a couple of spare drivers that will work with that voltage range you could have. Soldering it together is simple the fun bit is deciding on the body of the light.

    Posted 13 years ago #

  6. DaveC
    Member

    You can buy a 3volt regulator from maplins, at the power you need.

    Posted 13 years ago #

  7. steveo
    Member

    Yeah but you wouldn't get it to fit in the battery box

    Posted 13 years ago #

  8. DaveC
    Member

    Maplins:
    Regulator LM317
    R1: Variable Resistor 500k N44BR
    R2: Rixed Resistor 560K M560K

    Connect up with a little veroboard (JP54J) and a soldering Iron, and then connect to battery and multimetre and adjust the Variable Res with a terminal screwdriver until the output is what you require.

    Posted 13 years ago #

  9. DaveC
    Member

    @ Steve, not a reguator kit but 3 discrete components.

    Posted 13 years ago #

  10. steveo
    Member

    I defy you to get a 317 circuit into the battery box of a aa light ;)

    Besides by the time you burn the over voltage off the efficiency would be terrible. You would need to drop about 1.5v at probably about 100ma for a blinky, that's about 0.15w before the losses in the regulator. The power being delivered to the blinky is only about .25w assuming 2.4v at 100ma. Given the only reason to use this battery over a pair of nimh batteries would be increased run time loosing nearly 40% of the power as heat is far from ideal.

    Posted 13 years ago #

  11. Uberuce
    Member

    Ah, I forgot about this thread. Proposed location is the shell of this bike's light...

    Posted 13 years ago #

  12. steveo
    Member

    If you can get a 2xAA battery holder in there I've got a small 750ma driver that's only about the size of penny that'll probably fit, glue to the batter holder. Then you just need to work on the emitter.

    All this talk of "upgrading" old style lights has made me want to have a go... I'll add it to the list of stuff to do.

    Posted 13 years ago #

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