Alternative power source for bicycle headlight and rear light

Depending on the Vf of the LEDs, you could probably wire them in series on the appx. 6V, with an appropriate series resistor. Of course, check each lamp for a resistor in the circuit when you hack them. ;-)

Cheers! Rich

Why not use rechargeable batteries?

Aidan

sure and while you're at it, why not put a generator on one of the wheels? Too recharge it!

The lamps are already running on 6 volts...simply connect them in parallel to a 6 volt source such as a lantern battery...it has plenty of capacity for a long run time. This will eliminate the low capacity AA cells.

You might consider a blocking oscillator design which you could house in the battery box. There are many examples on the web.

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Wiring LEDs in parallel is almost never a good idea. Searching this group's archive for *current hogging* could be instructive. As has been mentioned, a series configuration is generally preferable with LEDs.

As has been mentioned, figuring out what presently limits the current would be a good plan.

The OP seems to indicate that each lamp has its own dropping resistor, and works off 6V, so a parallel connection is appropriate. If they were just naked LEDs, then of course the series connection is better.

Cheers! Rich

Connect the light units in parallel, not the LEDs. I thought this much was clear when I described using a common 6 volt source for both units.

An LED rewire is likely in order if you opt to use a blocking oscillator design.

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Thanks Rich...you got it exactly.

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Four AA cells is about the same as three lead/acid cells: get a

6V gel cell rechargeable battery for this. Most generators have chassis GROUND and AC output, you'll need capacitor and two diodes to make a voltage-doubler rectifier for that (the generator sets don't produce too much current, probably you can wire directly to the gel cell without any limiter).

You have come the closest to what might be best.

Can the gel batteries be charged many times?

I have some step down transformers I took off various devices. May have a 6V one that can be modified.

I would like the battery to be more cost effective than NiMh batteries.

Thanks, Andy

d

I don't need any modifications to the LEDs. They are already in a working headlamp and backlight.

Andy

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ong

the

Lantern battery's higher capacity would be good .

It would be easy to take off to reduce weight when I don't need it. My bike weighs 43 lbs. now.

Don't have a car right now, so my bike is my car. :-)

Andy

Yes, they can.

I would add one thing: When a power source is constantly connected and spends a lot of time able to charge the battery, I would add a voltage regulator circuit to limit charging of the 6V lead-acid battery to 6.9 volts (conservative, in case charging is common and the battery does not encounter being deeply discharged).

A more aggressive voltage to get the battery more completely charged is

7.1-7.2 volts. However, 6.9 volts is a more conservative voltage that gets the battery somewhere around 85% charged and avoids electrolysing the water in the electrolyte. (There is a temperature coefficient to this, and I don't remember it.) If you want super-conservative, you could go for 6.8 volts.

You can make your regulator circuit a low-dropout type that has minimal requirement for the supply voltage to exceed the output voltage, and to continue to pass current even if the input voltage is below regulation target as long as output voltage is lower still. This only requires a good P-channel power MOSFET, an op-amp such as a section of an LM324, a few resistors, a voltage reference (I like 690-700 nm red LEDs, such as many Panasonic ones available at Digi-Key), and not too much else besides some tinkering and creativity and good attitude.

For bike-generator-powered, I like lead-acid and Li-ion. Lead-acid is easier. Li-ion is lighter weight, but requires special circuitry due to zero tolerance of overcharging to the extent of outgassing and zero tolerance of overdischarge, while lead-acid merely suffers a bit of degradation from minor overcharging and overdischarging followed shortly by recharging.

Ni-MH is good for bike lights, but good for recharging off-road. They don't like overcharging a lot, and detection of "full charge" by "smart chargers" tends to be based on detecting directly (by temperature) or indirectly (by voltage) a temperature rise that occurs when overcharge begins. This works better when charging current is sufficient to recharge these from empty to full in around or less than 4 hours. Packs of NiMH cells larger than AA will probably work OK with "smart-charging" that takes 5 or 6 hours.

They also want avoidance of being discharged below 1, maybe as high as

1.1 volts per cell in series strings, and no Ni-MH cells to be overdischarged past zero cell voltage by other cells in series with them.

--
 - Don Klipstein (don@misty.com)

My main "commuting car" and my main "delivery truck" for my "day job" weighs 24 pounds, including basket, excluding lights, excluding the fenders (likely 1 additional pound) that I ought to add to increase my comfort of riding in rain.

My youngest brother described it "back to me" as being "almost as simple as an anvil". I think this vehicle is not much more delicate than one.

I probably have 30,000-35,000 miles on it already in 4 years. I expect this vehicle to last at least another year or two more.

This tough vehicle is a Bianchi Pista. My main customization of it is to regear it to a slightly lower gear ratio - still good for top speeds of

35 MPH when I am the one driving it. And, at age 49 I often outrun cycling team guys on road bikes and bicycle messengers on track bikes with higher gear ratio going uphill, often also on level road, while my clothes are less aerodynamic, my bike has a basket, and my bike has only one gear ratio ("passing gear"). Part of this is attitude and part is experience, with lots of practice - I use this vehicle for a major part of making my living, as well as a majority of my commuting to my "day job". Oh, and did I say "attitude" enough?

--
 - Don Klipstein (don@misty.com)

Most likely you can run a cable from the battery compartment of one to the battery compartment of the other and just use one set of AA cells.

Doing this in such a way that the lights can stillbe removed could be tricky.

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Interesting information.

Do you have a horn on your rig?

Have you considered carrying a short range cell phone jammer?

Andy

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Mount neodymium magnets to the wheels and put coils on the frame - then spend months designing an efficient battery charging and monitoring scheme. Or just buy a hub mounted generator for ~$300.

Rechargeable batteries and charger, are probably the practical solution.

You gave me an idea.

Solar cells to be used for my lead acid battery.

Andy