Powering LED's with NiCD D cell batteries for bicycle.

romeroom

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I have 4 D cell NiCD batteries that are brand new. Each D cell battery is 1.2 volts. (They came with a charger)

I would like to use those batteries to power 4 of these or 4 of these flashlights together. Each of those flashlights are powered by 3 AAA batteries. Essentially I would put 2 lights in front and two in the back of the bike.

(I also have an additional 2 D Nicd batteries, but would prefer to keep it at 4.)

Is this possible? I suspect it is possible but what would it take to make it happen?

A few things to keep in mind:
  1. I understand there are a number of options out there for bike lighting. My philosophy though is to make the best use of the stuff I already have; I acquired these flashlights and batteries completely free of charge.
  2. I have some electronics knowledge, but not enough to figure out this issue with "doing the math. I can proceed with trial and error by connecting the lights to the batteries (parallel or series? help) mediated by a potentiometer/variable resistor and crank it until it looks as bright as if each flashlight had their own 3 AAA battery supply. However, if any of you can direct me in a possible way of doing it right, I would prefer that.
  3. I don't go on very long bike rides at night. I don't need the brightness to be very high nor do I need it to last a long time.

Thanks for your support on this.
 

ssanasisredna

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I get the DIY, but odds are you will spend more money trying to cobble something together that you are never quite happy with ... especially the mounting, versus just going out and buying some cheap bicycle lights with mounts which are quite inexpensive on Ebay/Amazon/Etc.
 

romeroom

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I get the DIY, but odds are you will spend more money trying to cobble something together that you are never quite happy with ... especially the mounting, versus just going out and buying some cheap bicycle lights with mounts which are quite inexpensive on Ebay/Amazon/Etc.

I appreciate the advice. I was just looking on Ebay and you can get something from Malaysa that includes turn signals for less than 5 dollars. There is the hassle factor as well. The cobbling of stuff together I don't mind and have much of it figured out. (I'm old and kinda like these projects.) I will give more thought to your suggestion, though. Thanks.
 

Lynx_Arc

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5mm LEDs are good for a short distance but typically they are more suited for flood lighting and dim long running flashlights but for a bike to "see" out there forget using them regardless of how many you can put in an array the only way to go is with Cree type emitters. Even Chinese clone LEDs are far superior than a shower head of 5mm LEDs for bike lighting. As far as cobbling stuff together my advice is finding 3 cell emitter (non 5mm) lights with decent output ratings or 18650 type lights. These lights can be driven by 3 of your D cell nimh batteries without additional considerations if you go with 4 cells or more you will have to add circuitry to reduce the voltage.
For turn signals and brake lights the red 5mm LEDs are just fine IMO and can be had cheaply
 

romeroom

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5mm LEDs are good for a short distance but typically they are more suited for flood lighting and dim long running flashlights but for a bike to "see" out there forget using them regardless of how many you can put in an array the only way to go is with Cree type emitters. Even Chinese clone LEDs are far superior than a shower head of 5mm LEDs for bike lighting. As far as cobbling stuff together my advice is finding 3 cell emitter (non 5mm) lights with decent output ratings or 18650 type lights. These lights can be driven by 3 of your D cell nimh batteries without additional considerations if you go with 4 cells or more you will have to add circuitry to reduce the voltage.
For turn signals and brake lights the red 5mm LEDs are just fine IMO and can be had cheaply

Thanks for your expert reply. You and the other responder make a good point about the functionality of these lights in their use as bike lights. I am less concerned about "lighting the way" similar to a motor vehicle and more about being seen. If you or others feel that a standard bike reflector's functionality would be degraded by cobbling these flashlights together, please say so and I will abandon the project.

I would simply like to know if it is possible (and how) to connect 4 of these flashlights to the D cell NiCD batteries I have.

Thanks again.
 

Lynx_Arc

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Thanks for your expert reply. You and the other responder make a good point about the functionality of these lights in their use as bike lights. I am less concerned about "lighting the way" similar to a motor vehicle and more about being seen. If you or others feel that a standard bike reflector's functionality would be degraded by cobbling these flashlights together, please say so and I will abandon the project.

I would simply like to know if it is possible (and how) to connect 4 of these flashlights to the D cell NiCD batteries I have.

Thanks again.
I think the problem with using a bunch of 5mm LEDs to be seen is that you may have more problems not distracting (possibly blinding) motorists and having shorter throw range may have those noticing you by the light alone less time to react. A high power emitter properly focused via either reflector or optics can throw a beam a lot farther away and that beam is noticed often before the bike gets there to be seen..
As for connecting flashlights together it is a matter of the battery setup. In the case of 18650 lights often you can unscrew the head separate from the body and solder wires directly to the driver itself. You could also use a dummy cell to get the connection to the + terminal down in the tube and somehow attach to the battery tube for the ground or drill a hole in the light and solder to the - spring terminal. For the 3 cell ones similar fashion. You can connect these lights in parallel and run 1 or all of them at once if needed. If you buy a bright enough light you probably don't need 4 of them 1 or 2 should do fine.
 

romeroom

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UPDATE

I want to first of all thank those of you who have responded, especially with words of wisdom. Even though for me this is just a small project for an old man, each of you drive home the importance of functionality and the hassle involved into what I'm trying to do. I appreciate this immensely. That being said, a near unlimited supply of cheap, free LED flashlights still scratches at my desire to use them to provide lighting for my recumbent bike (similar to this), even if its for nothing more than decorative purposes. (I was thinking about positioning them to simply point to the ground.)

As it turns out, the D cell NiCD batteries I was planning to use are pretty much dead. I got them out of storage where they sat for 10 plus years. So...

In the spirit of the original question, I want to know--beyond just experimentation--how to connect these flashlights to a rechargeable (battery) source. Ultimately and ideally, I want to be able to come home from a bike ride at night, put the bike in the garage, and plug in for recharging.

So, the supply of flashlights exists, I just need to know more about connecting them to a simple rechargeable power source. In other words, if for example I want to connect 4 of them (or more) how do I calculate how much power I need?

One potential obstacle is my lack of knowledge about LEDs--their electronic properties, that stuff about forward voltage, driver, etc. I suspect the simplicity I'm looking for doesn't exist, which is why I'm reaching out to this forum. I understand there are numerous places on the internet that provide instruction on these types of things. I will eventually go that route. However, forums in my opinion can bridge the gap between novice and expert.

If the nature of my questions falls short of the scope and expertise required to participate in this forum, please let me know. I have gained much already.
 

ssanasisredna

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Those lights you linked to are "good" with 3x alkaline putting out about 4.3-4.5V when new (allowing some drop for loading). They are nothing but batteries, resistors and leds. 4x new NiMh (likely easiest solution) will be about 5-5.3V off the charger with some loading. A single lithium (standard) is going to be 4.2V. Efficiency is not a huge concern and I prefer a bit more voltage so I can use a resistor to reduce output ... or likely in your case, the wires you use (no need for big conductors for the most part). Worst case you are going to run the LEDs a little hard wiring the 4x NIMH into where 3-Alkaline is standard. You said you had a limitless supply ... so the odd failure should not be a big deal. There are a million ways to do this, but you NiMh are readily available as well as the chargers, holders for 4xAA, etc.

I would start with 4 - NiMh
 

romeroom

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Those lights you linked to are "good" with 3x alkaline putting out about 4.3-4.5V when new (allowing some drop for loading). They are nothing but batteries, resistors and leds. 4x new NiMh (likely easiest solution) will be about 5-5.3V off the charger with some loading. A single lithium (standard) is going to be 4.2V. Efficiency is not a huge concern and I prefer a bit more voltage so I can use a resistor to reduce output ... or likely in your case, the wires you use (no need for big conductors for the most part). Worst case you are going to run the LEDs a little hard wiring the 4x NIMH into where 3-Alkaline is standard. You said you had a limitless supply ... so the odd failure should not be a big deal. There are a million ways to do this, but you NiMh are readily available as well as the chargers, holders for 4xAA, etc.

I would start with 4 - NiMh

Thank you. Pardon my ignorance (again): In your suggestion, you mention 4 NiMh batteries--possibly AA. You say a single lithium battery is/can be 4.2 volts correct? (is that the 18650 battery I see online?) So, to power 4 of these flashlights, you are suggesting 4 of these NiMhs, correct?

Again, my apologies if I'm not getting this as quickly as I should.
 

Lynx_Arc

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I'm not the person to advise you in the wide varieties of bike lighting. I will tell you that with most lighting needs there is no one solution that fits all desires as many people want different levels of differing types of output. From my reading here and there I've seen that many people have gone to a battery pack bike light solution. These setups are out there to be bought with little work to set them up to work and use from what I've gleaned. I think the biggest issue to start with for you is actually how much light you really need for how long between use times and down time to recharge batteries there is. Without this information you could end up with too much light or too little light and a battery pack that can't keep up with your needs even.
Here is a section of the forum that doesn't seem to have a lot of action about bike lighting. I'm sure if you were to search the internet you could probably find a bike type forum that has a lot of traffic in the LED lighting area for better advice.

http://www.candlepowerforums.com/vb/forumdisplay.php?86-Bicycle
 

romeroom

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I'm not the person to advise you in the wide varieties of bike lighting. I will tell you that with most lighting needs there is no one solution that fits all desires as many people want different levels of differing types of output. From my reading here and there I've seen that many people have gone to a battery pack bike light solution. These setups are out there to be bought with little work to set them up to work and use from what I've gleaned. I think the biggest issue to start with for you is actually how much light you really need for how long between use times and down time to recharge batteries there is. Without this information you could end up with too much light or too little light and a battery pack that can't keep up with your needs even.
Here is a section of the forum that doesn't seem to have a lot of action about bike lighting. I'm sure if you were to search the internet you could probably find a bike type forum that has a lot of traffic in the LED lighting area for better advice.

http://www.candlepowerforums.com/vb/forumdisplay.php?86-Bicycle

Perfect. Thanks.
 

romeroom

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Here is an example of what I wish I could figure out on my own:

I have an extra one of these 18 volt drill batteries. How many of those small (3 AAA flashlights) can I light by simply connecting them (series/parallel)?
 

Lynx_Arc

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Here is an example of what I wish I could figure out on my own:

I have an extra one of these 18 volt drill batteries. How many of those small (3 AAA flashlights) can I light by simply connecting them (series/parallel)?

If you get a buck converter you can run a few of them depending on the current draw. I wouldn't try to run a bunch in series as 18v batteries are actually closer to 21v when fresh off the charger.
 
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