9v PP3 keychain pocket rocket?

MikeHunt79

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Ok, I'm planning to build this from scratch. How about this for a keychain light for occasional / emergency use?

9v pp3 (probably alkaline, maybe NiMh) battery, direct driving a lux V at around 900mA, with a resistor. I already have the Lux V and it has a Vf of around 7v. It won't be very efficient, but runtime is not really an issue for me with this light... Size is the main concern.

I was thinking a 20mm colimator would be best... probably a 2 degree carclo one... I've already got a machined MiniMag head I can fit this in.

Would a Alkaline be capable of outputting high current needed, or would a NiMh be a better option here? Also, I'm guessing I'd need resistors with higher current than normal current ratings.

Also, where can I get metal (preferably alu) PP3 holders? I was hoping to make it act as a heatsink as the Lux V's get hot. :)
 

Planterz

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I can't help you with all the technical stuff, other than to say that if this light is for emergency/ocassional use, go with lithium batteries. Alkalines will eventually self-discharge, can leak, can't drive much juice and don't work well when cold. NiMH self-discharge even faster than alkalines. Lithiums however can drive current hard, have a 10+ year shelf life, and work fine when cold. NiMHs should work fine for regular use, but don't rely on them for emergencies.
 

MikeHunt79

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Ok, thanks... I've managed to get quite a good deal on some "Ultralife" PP3 lithium batteries, so I ordered 20. I didn't see a max current rating on the site, so I hope they will cope. Do lithiums batteries drop voltage as they are used like lithiums or do they hold thier voltage like NiMh's?

Now, I just gotta figure out where to get a holder, and work out what resistors I'm gonna use. :)
 

offroadcmpr

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MikeHunt79 said:
Ok, thanks... I've managed to get quite a good deal on some "Ultralife" PP3 lithium batteries, so I ordered 20. I didn't see a max current rating on the site, so I hope they will cope. Do lithiums batteries drop voltage as they are used like lithiums or do they hold thier voltage like NiMh's?

Now, I just gotta figure out where to get a holder, and work out what resistors I'm gonna use. :)

there is some voltage drop, more than a nimh, but less than a alkaline.
 

MikeHunt79

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offroadcmpr said:
there is some voltage drop, more than a nimh, but less than a alkaline.
Any guesses on how much drop would there be roughly at 700ma draw? As long as it doesn't go below 6v I should be ok. :)

If theres too much drop, I could always use NiMh but I'd have to always keep the battery charged.

Also, I reackon I might be able to modify an existing 1xAA torch body to accomidate a pp3.
 
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