bcubed

I have a 6V, 3W Union-brand bottle generator (actually an alternator) that I've hooked up to a Ni-mh battery pack for redundancy and 0mph illumination.

What I was wondering is: I wanted to be able to run car-based electronics (such as GPS and cell charger), which are all 12V. I also wanted to run more lights. I saw online that a gen is really a current-specific, not voltage-specific, device, and it described how to run two std. lights in series.

The problems that I noticed are 1. use of a voltage-limiting diode and 2. "saturation" of ferrous materiel in the gen such that it "tops out" at some point. For 1, I could just eliminate the diode, but for 2, I imagine I'd have to add ferrous metal to the gen guts. Is this (hopefully) as simple as locating steel w/ a magnet, then wrapping a few strands of bailing wire around?

n4zou

Any bicycle dynamo will power a USB device. Here is the circuit I use.

You can't power 12 volt automotive accessories. USB port computer standards just happen to be close enough to a standard bicycle dynamo that a simple bridge rectifier and 4 Ni-MH batteries are all thats required to convert AC to DC, regulate, and filter power to safely power a USB device. Some cell phones and most all modern GPS units can be powered and recharged through a USB port. Just make sure you use solder tab batteries with no possibility of a poor or open connection which would allow unregulated power into your device.

bcubed

TY, n4zou. I didn't realize that USB ports were usable for power only (i.e. no data xmission). That'll work for my GPS, though not nec. my phone (no USB, but I haven't checked yet to see if the cig-lighter adapter knocks down the volts any--know it doesn't on the GPS at all.)

What piqued my curiostiy was this site, that mentioned stagnation as due to "limiting the amt. of ferrous material surrounding the windings." I've seen graphs that show gen power output as roughly proportional to speed until 12mph or so, and then flattening out. I thought adding more steel would inc. power output during descents (i.e. when I least mind the loss), so that I could either run more lights, or perhaps run a bigger dia. roller, such that power losses during slow-speed ops (when I most mind the losses) would be lessened, even as average power would be maintained.

In the interest of science (and 'cause I like taking stuff apart), I'm going to try this mod and report back...

n4zou

Modern bottle dynamos usually provide peak current at 7 MPH on a 700 wheel and about 5 MPH with a 26" wheel. Some dynamos produce more than 500mA. I have a cheap Schwinn dynamo I found on sale at Target a couple of years ago that pumps out 700mA. It's nice in that it really makes my Cree Q5 LED light really bright. If you really need 12 volts and more current you might try a stepper motor setup. The only problem may be drag, lots of it! A 500mA dynamo is not very bad but a big stepper motor cranking out an amp or two may not be much fun. Here is a link to get you started in that direction if your interested.
https://www.instructables.com/id/Bike-Generator/

bmorey

This DC-DC converter module is a possibility. It should be obtainable in the US --

https://preview.tinyurl.com/62cr57

brotherdan

seriously though, those union generators are so draggy, they slip so much at the slightest sign of precipitation, and their power output is so low, that you're really wasting your time even messing around with one.