Diy dynamo flashlight

Why not solar, suitable charger, and 2 or 3 spare cells? Much less work than cranking.

I would like to have the light ready in any emergency. If I have a power outage in the night, a solar light wont do me much good. I do own a solar panel, which I could use to charge batteries for my flashlights, but I am looking for a solution that doesnt need any preparation.

Wellp, I got a set of these

https://www.amazon.com/dp/B08NPYHHPG/

but can’t really use them for their intended purpose (mounting plate + shade), so I have them as motion-detecting cat-lights by their litterbox.

One’s on “active duty” near the box while the other sits on the windowsill charging up. Low battery on A, swap for B and put A on the windowsill, and v/v.

Point being, lots of those doodads have solar cells, a battery, and the associated charging circuit. You wanna go crazy and put bunches of batteries in parallel for long runtime, it’s pretty simple, and always ready.

Not really what I am looking for, but that would be an option to have a light “always ready”. How long would a LiPo battery survive in such an “always charged” state. It would be bad, if I bought it for an emergency and the battery doesnt have any capacity left.
Thats the main reason, why I was thinking of using super caps

Supercaps can be limited as far as discharge current unless specially designed for it. Maybe a 5mm LED but not more.

Am I the only one that does not know what a dynamo flashlight is?

I dont know if it is the correct name. It’s a flashlight with a crank and a very dim led

Oh

This is unrealistic, a hand crank won’t power a 300 lumen flashlight for long.
My emergency kit has two packs of NiMH AAs and two AA powered flashlights.
And a NiMH charger.

One can add some solar and a powerbank if they want but its not necessary.

A super capacitor won’t run the light long unless you only want moonlight mode. They just can’t hold much juice.

I know, it cant produce so much light for long
I was hoping for something like a Minute or so

What if you powered the crank by a cordless dewalt drill?

I can only wonder how many lumens would you get if you spun the crank at say 10,000 RPM. Would it ever equal an FT02S?

Why use the loss of conversion of Dynamo when you could just tap the Dewalt battery straight up, with step down buck of course.?

I’m not saying don’t build one, I love the creative builds people show here on BLF, but for your intended use, the last thing you want to be doing during an emergency, is messing around trying to crank charge a light. An ‘off the shelf’ light is likely to be more waterproof, and potentially more reliable than a self-built crank light.

CR123 or AA lithium cells used to be the go-to ‘fit and forget’ power source for emergency lights if you’re worried about cell discharge.

Li-ion cells generally hold charge quite well, I’d say that a Convoy S2+ with Sst-20, 3x7135 option and a decent 18650 or two would be suitable.

Ok I see, that the flashlight doesnt make sense for this use case, but I would really like to build it anyway. As far as I know, Super caps can provide really large currents, thats why they are used to store breaking energy in f1 cars. I was thinking of using something like a 3.8V 100F cap. This should be able to power a cree xpl at 500mA for more than a minute. or did I make a mistake here somewhere?

You could start with an existing product and add the capacitor.

https://www.amazon.com/Kaito-Powered-Emergency-Flashlight-Cellphone/dp/B003A21DQA

good idea, someone on fonarevka .ru build one, using cordless drill motor and gearbox as a generator, it was making enough power to light up xml at max current. without much effort
http://forum.fonarevka.ru/showthread.php?t=5336

That is really helpful, Thanks
I have an old cordless Drill lying around, I will try it

It actually worked
I now have a “generator” that can provide up to an amp to a cree xp-l. Its the only LED i currently have at home. Is there a disadvantage of using this LED also for the really low power mode?
Is a 5mm LED more efficient at currents of about 10 mA?
I was thinking of using 2 different cirquits, one for low and one for high. For low, just a 50-150 Ohm resistor in series with the LED, I know its inefficient, but i think its fine, for high 1 7135 without a microcontroller. If I am not mistaken, this should deliver 350mA to the LED, which should be bright enough I think. So I now only need the super cap and a way to charge it

you’ll be better off with single led and 2 modes

Thats the plan so far, I was just planning to use 2 different cirquits connected to the same LED.