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I have a large supply of NiMh rechargeable batteries that I use for all my gadgets. I have several small very bright LED flashlights that use these. My question is how can I construct, from parts, a strong bike headlamp that uses such batteries? Based on review of many product recommendations offered, I have not found a 300+ lumen light, so I'm looking for a way to construct such a light. It would need to be easily detachable so I could remove it when locking the bike in public.

I am interested in solving the problem of getting such a light, either buying or constructing such a bike light, by someone who has done this and tested it successfully, not a "which brand is best" product recommendation. I would think that pointing me to a general approach and/or a general place (links, marketplaces, etc.) where I could find such items would also answer the question without violating the norms, as long as they are fact based (e.g. successfully used by someone to solve this specific problem) and avoid naming specific brands or models. I don't know or care about electronics because it's beyond me how to put together circuits or LED's, I just want to understand how to get components that can be combined to attach and mount something very effectively and waterproof to a bike. I'm not looking for instructional material or training on bicycle repair or how to upgrade a specific kind of bike. Just how to solve a problem.

I'm just kind of a clueless dude here trying to ask how to go about this, looking for different approaches, some involving DIY and some involving using framework approaches, and letting people vote on which approaches worked best for them. (See https://stackoverflow.com/questions/9329446/for-each-over-an-array-in-javascript/9329476#9329476 for an example of this kind of a question/answer dynamic on a different StackExchange type site.) If that's not the intent of this site I guess I get it, keep the question closed. I put up a question in meta about whether this question is appropriate and so hopefully, as this is closed, the discussion on the appropriateness of this kind of question can be contained there.

One other thing is I'm looking for inexpensive way to go about this; $200 is out of my range.

I want to just point out that I am approaching this as an engineering problem with a bunch of requirements and looking for empirical evidence to support a solution. I am hoping the fact that some components involve electronics or that there are cost constraints does not take this out of the realm of ordinary bike problems.

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    What do you mean by "get"? If you mean "buy", then shopping questions are off-topic. If you mean "make" then you're asking about electronics, not cycling. – David Richerby May 16 '19 at 16:05
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    Why not just use the LED flashlights you have? In which case you could ask the question " How do i attach these to my bike " or " Can these be mounted to my bike " – Dan K May 16 '19 at 16:13
  • Also note 300+ lumen would probably be too dazzling for oncoming traffic, unless the law has changed with another revision in the UK the minimum is 4 candlepower which is the equivalent of 50 lumen, nothing to say you can't use more just don't dazzle oncoming traffic – Dan K May 16 '19 at 16:19
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    @DanK 300 lumen in a well shaped beam is the minimum you'd want for riding at a decent speed on unlit roads. 300 lumen from many torches (flashlighs) would be dazzling for other users even if you pointed it mainly to illuminate where you're about to put your wheels, while at the same time being inadequate for trail riding. – Chris H May 16 '19 at 16:24
  • I think this is actually a reasonable question - or rather includes one. Multi-night rides would require the same solutions if not using a dynamo and without charging facilities. A DIY approach would also be on topic at the electronics site but that's not inherently a problem (a home made pannier would be on topic at crafts, for comparison). – Chris H May 16 '19 at 16:43
  • Philips SafeRide 80. One of the strongest street legal headlights and it uses 4 AA cells. – Michael May 16 '19 at 18:17
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    @Michael your comment exhibits one reason why product-rec is off topic. One cannot claim something is legal without saying where it is legal, which is very likely a different place to OP. And such an item may not even be available to OP's location. – Criggie May 17 '19 at 07:59
  • @john consider using permanently-fixed lights, that are bolted onto the bike. Then you would run fixed wiring to a battery case that can hold a bunch of your rechargeable cells. – Criggie May 17 '19 at 08:00
  • I just don't understand why this keeps getting closed. I have a problem with fairly discrete requirements, I am trying to solve. I am not looking for a product recommendation, I am looking for a solution to a bicycle problem, that cannot be easily solved. Why is that off-topic? –  May 23 '19 at 14:53
  • @DavidRicherby Hey David, I am asking about how to affix parts to a bicycle. The electronics part would have to come from parts that have already been assembled. –  May 23 '19 at 15:03
  • @Criggie thanks for your feedback and does a question on how to construct a bike part constitute a product rec? –  May 23 '19 at 15:07
  • @JohnMeyer How were we supposed to know that? Nothing in your question says it’s about attaching anything to anything else. Your question says you want to “get” a particular kind of bicycle light. I asked what “get” means and you never explained. Now, your question seems to be about making a particular item, and the bicycling part seems incidental. What do you want to know that can’t be answered by looking at existing products? – David Richerby May 23 '19 at 15:07
  • @DavidRicherby Thanks for that point. As evidenced by the responses, there does not appear to be such a product, except for maybe the Phillips, which is $199. That's a little less than I paid for my bike. –  May 23 '19 at 15:09
  • @Michael Thanks for the recommendation and I can't afford the Philips at $199. :( –  May 23 '19 at 15:17
  • @DanK Hi Dan, I ride my bike around a lake after dark with my Belgian Shepard. There are coyotes that are chasing us, and my dog is sometimes trying to chase them, which sometimes causes the breakaway leash to snap. This is not expressly for road use as the coyote part of the path is mostly far from the road but it would be helpful to be able to dim the light if that's possible. –  May 23 '19 at 15:23
  • @DavidRicherby Hi David, thanks for helping me to understand the rules of this please. I'm looking for how to build something that has fairly specific requirements that's not so exotic it's too expensive on the general market. Like, for example, how to build a bike with an accommodation for someone with one partially paralyzed leg or something like that. (A family member needs that but that's a future question.) The accomodations I need are financial and ecological. –  May 23 '19 at 15:28
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    There's a good reason most manufacturers have moved over to Lithium batteries. They have better energy density, and better tolerance to high current applications than NiMH. Most users are demanding 500+lm now, and the current drain to produce that would exhaust a 4xAA pack in a very short time. You might be able to get some help at candlepowerforums which is full of LED light enthusiasts – Andy P May 23 '19 at 15:31
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    Hi All, to avoid crowding this comment thread I've created a post in meta to talk about the appropriateness of such questions as this, which is seriously something I am also interested in! –  May 23 '19 at 15:43
  • Well I found this: https://www.instructables.com/id/BIKE-LIGHT-500-Lumen-%2522Mt.Bike%2522-for-under-10-bucks-/ and also this: https://www.instructables.com/id/DIY-Bike-Lights/ – Swifty May 28 '19 at 21:11

2 Answers2

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As suggested by Dan K, you might use the LED flashlights that use NiMh batteries you already have. Assuming that those are bright enough for your needs, you could get bike mounts for flashlights (a quick search on amazon.com for flashlight bike mount reveals plenty of options).

These mount on your handlebars, and are small enough that you could fit more than one and point them at different angles, to get more side visibility as needed and a bit downward to avoid blinding other people heading your way, as a way to compensate for the improper beam shape your lights may have, which is a great point Chris H raises.

PhilippeAtM
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  • This is a pretty promising provided the beam shape is okay and I can build a quick-release mount. I'll give it a try. –  May 23 '19 at 15:16
  • A helmet mount is more tolerant of a non-cycling beam shape than a handlebar one, as at least if you can zoom it in narrow then you can aim it at the patch of ground that matters, and position your head to keep it out of others eyes. – Chris Stratton May 28 '19 at 21:29
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Until recently there were a few high quality lights running off such cells on the market, but they've been discontinued, and anyway were expensive. This means you'd have to make something. If you're not happy with the DIY aspect (soldering and waterproofing) of this, the project probably isn't for you.

Many front lights, including some with good beam shapes, are designed to run off lithium rechargeable packs. These put out roughly 7.4-8.4V. You may get away with 6NiMHs in series but you're more likely to need 7. You'd have to make up a pack, and a holder for 7 cells is uncommon.

There are other lights designed to run off the 5V of a USB battery pack. These are likely to run off 4 NiMHs in series (for 4.8V nominal) but good ones tend to be expensive. Again you'd need to build your own pack around a 4-cell holder. They should, in theory, run off an AA emergency phone charger (such things exist and by coincidence ice for one on order) but I haven't tested that. You could avoid any construction by putting the phone charger in a toptube bag.

Beyond that, lights that charge off USB tend to use a single lithium cell. This is a good match to 3NiMHs in series.

A good beam shape is important at this power, which is capable of dazzling other road users while simultaneously falling to illuminate your path.

Chris H
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  • I do have a such a phone charger. Any tips on how to affix items to bike with quick release capabilities? –  May 23 '19 at 15:12
  • @JohnMeyer I use a cheap toptube bag (with snacks on top of the charger). I leave the bag on the bike and take the charger out when I don't need it. The bag protects the charger from rain, though mine is supposed to be splah-proof. Some of these bags have a headphone cable exit port at the back (big enough for micro-USB), but I've cut another cross at the front to use a shorter cable. – Chris H May 23 '19 at 15:15
  • Do you use a bike light designed for use with a separate power pack or do you hack into a light that uses a propietary power pack? –  May 23 '19 at 15:20
  • @JohnMeyer currently I mainly use dynamo lights, and my main backup has a built-in battery. I also have one with a proprietary battery pack for my other bikes (that's waterproof and can be strapped directly to the frame but I find it more convenient to put it in the bag). Some of the people I ride with use the USB-pack solution, usually in a bag of some sort. – Chris H May 23 '19 at 15:41