Random idea for offboard CMOS batteries... old laser pointers! \ VOGONS

Random idea for offboard CMOS batteries... old laser pointers!

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First post, by BitWrangler

Posted on 2021-07-30, 02:16

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Hi folks,

In the junk drawer I noticed I had a couple of dead laser pointers, the generic keyring, cat distractor type. Guess the diodes burn out in the cheapies. What use are they I thinks... I know, CMOS batteries! just unscrew the head and solder on leads (bypassing button switch) and you've got a 4.5V worth of lithium cells holder. There's also a slightly shallower version of the batteries they take that might give you 6V if you stick 4 of them in. How long will they last? Dunno, probably not the 15 years of those square pack lithium cells, more like cheapie CR2032s probably. Posting this before I forget it, meaning to try it on the next board I find that needs one. They would probably mount to a case nicely with a cable clamp, or ferrite rod antenna holder, or just ziptie them somewhere.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

Reply 1 of 3, by mkarcher

Posted on 2021-07-30, 05:39

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BitWrangler wrote on 2021-07-30, 02:16:

In the junk drawer I noticed I had a couple of dead laser pointers, the generic keyring, cat distractor type. Guess the diodes burn out in the cheapies. What use are they I thinks... I know, CMOS batteries! just unscrew the head and solder on leads (bypassing button switch) and you've got a 4.5V worth of lithium cells holder.

The laser pointers usually use LR44/AG13 coin cell batteries, which are alkaline, not lithium. There is the SR44/SG13 silver oxide type, too, which has around twice the capacity and a lower internal resistance, but that type is too expensive for the cheap laser pointers. I never saw a lithium cell in that case format, though.

Reply 2 of 3, by BitWrangler

Posted on 2021-07-30, 12:09

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They are? Wow that's a heck of a thing to miss for years, thinking all button and coin cells are lithium 🤣

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

Reply 3 of 3, by dormcat

Posted on 2021-07-30, 13:03

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BitWrangler wrote on 2021-07-30, 12:09:

They are? Wow that's a heck of a thing to miss for years, thinking all button and coin cells are lithium 🤣

Take a glance on vintage camera communities, particularly on providing power for cadmium sulfide light meters. 😉

Side note: IMHO film photography has a lot in common with retro computing.

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