Charge while riding?

kevinkrg6 · Jul 2, 2011

Hi everyone.

I want to charge a 12v battery (for lights and horn) while I ride,
so that the length of time the battery lasts is extended.

I figured that a 12v dynamo like this:
Amazon.com: Bike | Bicycle Dynamo Generator 12V 6W: Sports & Outdoors
could somehow be wired into this.

Could it simply work like this?:

I was simply wondering if anyone knew how to wire the dynamo so that it can charge the battery while riding, or could point me in the direction of somewhere that had a wiring diagram.

rohmell · Jul 2, 2011

Add a diode so the battery does not discharge thru the dynamo when not in use:

kevinkrg6 · Jul 3, 2011

Would you be able to point me in the direction of what type of diode? (not very good at wiring or anything)

rohmell · Jul 3, 2011

Here's a nice heavy-duty 3 amp diode that you can use:
3A Barrel Diodes - RadioShack.com

nvmextc · Jul 3, 2011

You can't just hook up the dynamo to a battery, there needs to be a charging circuit inbetween to regulate the power to the batteries. Since it'll be 12v input rather than normal househould voltage you'll need to construct your own also.

GearNut · Jul 3, 2011

That is true if you want a true regulated circuit as needed with modern digital electronics.
For a bare bones basic charging system, all you need is doide.
Light bulbs are not that finicky.

kevinkrg6 · Jul 4, 2011

Ah, ok. I am not sure if I still want to do this then. Methinks the dynamos won't charge up the battery that much anyway.....

banzo · Jul 26, 2011

Sturmey Archer makes a front hub that generates 6V/3A while you're coasting. I'm looking for info on how to add a simple battery to store juice during the daytime ride and use it for LED lights at night? Any DIY sites that explain how to design a simple charging circuit for 4 x "C" rechargeable batteries ought to do the trick...

wayne z · Jul 26, 2011

Look at The Kobota dynamo in post 7 and 14, in the "car alternator" thread of this forum

H20rider · Jul 30, 2012

Okay...so how about a set-up using a 6 volt (new Sturmy Archer) dynamo to power both the lights (led) and a 6 volt horn? Yes, I get that the LEDs take ac and the horn takes dc.
My thought is to split the output from the dynamo. One circuit goes directly to the lights (ac), an the other circuit goes to a 6 volt transformer (wall wart) to produce the necessary dc current for the horn. Then adding either a rechargeable battery or a capacitor to the horn circuit would ensure reliable horn access even at slow speed or stopped. The headlight has a stand light so that doesn 't require the short term power storage.
Sound feasible? Other solutions? The white wire doesn't seem likely to power the horn, but......
Thanks in advance.

Pilotgeek · Jul 31, 2012

LEDs take DC. You can run an LED on AC because an the D in LED stands for diode, which is a type of rectifier. So an LED actually rectifies itself from AC to DC.

Using a wall-wart will not work. A wall-wart is designed to convert 120v down to a lower voltage. If you want to convert AC to DC, have a look at my step by step instructions on how to wire up an ac to cd rectifier. It is intended for white-wire use, but it will work with your dynamo.
DIY Rectifier

I suggest you build that rectifier (or find a similar one), and connect the output from that to your horn, lights, and battery.

H20rider · Jul 31, 2012

Pilotgeek,
Thank you for the advice. I
've made the rectifier you described.
So, now a couple of extra questions.
What would you suggest as a good configuration given the items to be powered (headlight- taillight and a 6 volt moped horn) and the potential power sources ( 6volt hub dynamo and the white wire). ?

Lights and horn off the dynamo? If so, in parallel?
Lights of the dynamo and horn from white wire?
Some other set up?

As I mentioned the lights both have stand lights, but the horn has no reserve power ....which isn't really an issue.

Again, thank you for the help.
Gery

ivan H · Jul 31, 2012

I've tried a few setups, including running a 6V incandescent straight off the white wire. I'm currently chargeing a 6V 4.5A/H SLA battery thru a bridge rectifier made from 4x 40V 1A Shottcky diodes (less voltage drop than ordinary diodes), & running a 6V 26Watt Halogen lamp of it. This gives bulk light. I havent found out how long it lasts but 1/2 night ride & its still very bright. I keep a sanyo 6V 3Watt dynamo & light as backup but havent needed it. I really think the white wire/rectifier/battery is the way to go. Cheers

thegnu · Aug 1, 2012

That may work , just be sure to put a zeiner diode in line so the mag donesnt recognize any of your curcuits as a short or a ground an not let the bike start.

H20rider · Aug 1, 2012

The gnu,
What is the "that" in "that may work"? Pilotgeek's rectifier?
Is it Ivan H's set-up, or one of the options I mentioned using Pilotgeek's rectifier?
Also, where in the line would this diode go?
Thanks

Pilotgeek · Aug 1, 2012

I would not use a combination of white wire and dynamo, because they may interfere. Combining them on the AC side, you would want to put a diode on both the dynamo line and the white wire line. That would already rectify it, but at only half efficiency of both, so it's kinda pointless to use both. The only feasible way to use both would be to use two separate rectifiers for each power source, but they may "fight" with each other.

I would use only the dynamo. It won't effect engine performance, and I'm sure the dynamo is capable of putting out more watts. The only problem with the dynamo is that when you stop, it doesn't produce power, but if you have a battery it doesn't matter.

So Dynamo -> Rectifier -> Battery -> Accessories

You'll want a switch to be able to turn off all the accessories so you don't drain the battery. While I don't *think* the battery should leak through the rectifier circuit at all, it may be safe to put a large diode between the rectifier and positive terminal on the battery. If the battery dies after a few days of not using it, that would likely be the problem.

thegnu · Aug 1, 2012

That meaning I am a bit confused on your exact wireing layout , heres what works for me off the white wire only , zeiner diode , pilotgeeks rectifier , an a 12 v 7.5 amp hr sla batt all light bulbs are led , the battery has only needed charged 1 time an I do a lot of night riding at least 2 or 3 hours on the weekends any other time the bike is moving I have rear running lights, headlamp on low beam an a licence plate lamp on at all times .
the diode goes in line first be sure not to install it backwards they are marked by a small band of color on one end that band shows you that current can not flow from that side , but may flow from the other side

H20rider · Aug 1, 2012

Pilot geek-
Great. That all makes sense.
Do you have an idea of the battery I should use? I understand that horns are amp. thirsty. So, it seems there significant factors:
1. Size & weight ( smaller the beter)
2. amperes ( sufficient for a infrequently used horn)
3. Ability to be effectively charged by a dynamo

Oops...#4 factor----cost$$$
I realize a 6 volt photo battery probably won't work, but how about an RC vehicle battery? Or, do I need to go to a motorcycle battery?

It might be easier to strap a stray cat to the handlebars and pull it's tail when someone pulls out in front of me.

Also, what sized diode? (For the circuit, not the cat.)
Thanks for your continued advice.

H20rider · Aug 1, 2012

Thegnu- thanks for the clarification. I am just beginning to figure this vehicle wiring stuff out, so I get lost fairly easily.
Best, Gery

thegnu · Aug 1, 2012

no prob some circuts still baffel me too an work in an automotive trade

Charge while riding?

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