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I want to power a 4W 30V lamp with a battery that charges by a dynamo/hand crank generator.How can I do this? Answered

I want to power a 4W 30V lamp with a battery that charges by a dynamo/hand crank generator. For batteries, I want to use something like 3.7 V standard phone batteries, or may be camera batteries etc. I understand that I have to use a few phone batteries to get a decent amount of voltage which I can then step up to 30V to power my lamp. How can I go about doing this? How would you suggest to connect the batteries, and what kind of circuitry (buck/boost regulator, voltage step up, RC circuit etc. ) between the battery and lamp do you think is the best to use for outputting the right voltage? Thanks a bunch! :)


I assume the lamp you are talking about is incondesant, that it, it has an element in it just like the one above your head right now. My suggestion would be to find the light. (ha ha) Find the light that is more suited to your generator.
Try LED lights, put a few of them together and you've got yourself a pretty bright light! (no doubt) they are selling the flashlights down at the local gas station.
buy the cheep one ---tear it apart and see what voltage they use to run those little lights --- do the math and add or subtract till you get 8% under the voltage that what ever battery you would like to use is at and then you've got a light that matches your battery. then you can measure your little generator voltage and go down to radio shack and buy the resistor that puts your generator 1 to 1.3 volts over what the battery is at (fully charged of course) and then wire the resistor into the generator out put positive and you're ready to go, (maybe a couple minor adjustments but hey, if it works it works right!) hand crank away and be happy with all the exercise and really man, those LED lights are great! and they put out better light, brings out better color and shadows, especially when its pitch black outside.

Have fun!


9 years ago

Hello! Firstly, thanks for your (speedy) replies! :) Dear lemonie, you asked "Why 30V - is this necessary or could you use a lower voltage lamp?" Well, I was looking for a UVC lamp with a minimal power requirement so as to be able to run on power harnessed by a hand crank, and the lowest I could find was a bipin T5 G4 4W 30 V low pressure UVC germicidal lamp made by Sylvania. I would prefer a single end lamp however I couldn't find one yet. So yes, if I could get my hands on one I would use a lower voltage lamp. :) I thought of stringing the batteries together but I also doubt the ease of charging them. I don't strictly need to use cell phone batteries. If there is a battery I can get my hands on that suits the voltage requirements between the power source crank and the lamp then I could make use of it. Then I could also pinpoint if and what kind of transformer I need. Dear NachoMahma, Do you think the lamp I mentioned above would run on less than 30 V? I also assumed that it would be possible to harness 4W from a dynamo/ hand crank generator. The bike shops have 3W dynamos, and the hand cranks in LED flashlights output up to 5w (as they claim). I also saw 25W hand cranks on the web but they are a bit bulky(over 1 lb) and relatively expensive. My question is that, do you think it is possible to charge the battery this way with a dynamo/ hand crank generator, and then power the 4W lamp? Thank you! :)

I'm a bit stuck for a simple solution to this.


Same here... What is a less simple solution, if you have any in mind?

You could rig batteries in parallel, then step-up the 3.7 with some kind of transformer this type of thing but you might have to build it yourself.


> Do you think the lamp I mentioned above would run on less than 30 V? . Probably not. I was thinking of general illumination lamps. Check the lamp's datasheet to be sure. . . It's very possible, but you're going to have to crank for a long time to recharge a battery large enough to run your UV-C lamp for very long. For short-term use, it may not be a problem. You may be able to find some info on the 'Net that will give you an idea of how many minutes of cranking you will have to do to get one minute of light.

. A DC/DC voltage converter/booster (Google is your friend) is not a problem, but as L points out, hand charging a large battery may be difficult. . How long does the lamp need to operate between charges? This will determine how large the battery needs to be. . You can probably operate your lamp off of less than 30V, if that will help. 24V may provide an acceptable amount of light.

Hmm. You could string 8 x 3.7v in series, but you'd struggle to charge them. You could step-up the 3.7 with some kind of transformer (yet to be decided upon). Why 30V - is this necessary or could you use a lower voltage lamp? L