I needed to make a decent light on the cheap, which I started in a different thread.

I used one of those old Eveready flashlights (2 d cell type with the white switch, very common in the US) that I had lying around. I replaced the light bulb with a 5D cell (5V-7.5V) 5.5 watts, 4500K 150 lumens 920ma) bulb. I drilled 2 holes in the bottom of the flashlight and ran wires into it and soldered the pos directly to the bulb and wrapped and soldered the neg wire to the copper connecter that is part of the switch. I ran the wires to the back of the bike and put an 8 AA cell holder and put 6 2500mah 1.2V nimh cells(18 watt hours) in it with 2 dummy cells (just shorted the 2 cell spots with aluminum foil). The cell holder has pretty stiff springs, so I think the pack itself isn't deficient, and I'm pretty sure it's good enough for <1 amp

(Also, I moved the pack to back of the bike to free up the cage, I bought a small dog collar at the dollar store and am using it to hold the pack in place right above the rear brakes, can't even really see it, looks much better now)

Last night it was very dark and raining and I had brought along a spare set of batteries in case the ones I had died. With the ground wet and the rain and the poor lighting, I was having a really hard time seeing the road conditions ahead of me (I have it tilted so the main light is about 25 feet in front of me). Wanting to go a bit faster, took one of the dummy cells out and put another cell in it and it really, really helped and got me home that much faster.

Just out of curiosity today I put a multimeter across the cell pack with the light off and read 9V, pretty typical for 7 NIMH cells. But when I turned the light on, the volts dropped to 7.5 which is 1.07V ( down from 1.285)per cell, that's a pretty big drop. The cells are in a good state of charge and aren't old and are a decent brand. The 920ma draw is only .368C and NIMH cells should be able to sustain at least .5C or even 1C or greater. The only thing I can think of is that either the batteries are damaged, or the switch is making a poor connection to the bulb housing and causing too much resistance in the circuit (I guess I can check that). If so I can just solder the negative lead to the bulb and wire in a simple switch, or is this drop normal on such a low draw?

I know that nicads have much lower internal resistance, so I was thinking of replacing the battery pack with C sized 1.8ah ni-cad cells. This would give me less run time, but I could make up for the difference by putting 2 6 cell batteries in parallel, but I can't do that until my rack gets delivered. Since they are made of very light plastic, the weight is no big deal. Would you anticipate a similar voltage drop on a nicad pack?

This setup is working for me, but I don't want to damage the cells. Should I go and use the Nicads? According to the data sheet both the C and D cells are made up of a sub-C 1.8AH cell (they are the yellow Eveready D and C cells, they are identical)

Any suggestions?

You shouldn't damage your cells as long as you don't run them down to the point where one of them is almost completely discharged and starts getting a reverse voltage applied by the remaining cells. With 7 cells in series you want to make sure the cells are well matched to each other and recharge the cells well before they are fully discharged to avoid that situation. I'd suggest checking two things with your multi-meter. First, check the voltage across each cell individually when the light is on to see that the readings are uniform, and second, get a current reading when the light is on since 0.92A is just a nominal value for the bulb and will vary depending on exactly how much voltage is applied to it.

The voltage drop of about 0.2V/cell at a current of about 1A is a little high, but not by much (normal internal resistance of an AA NiMH cell is just under 0.2 Ohms).

Your thinking looks sound to me, that seems like that's too much drop for the draw you're presenting.

I will comment that you can get a really nice LED flashlight with two 18650 cells and a charger off eBay for < $20. I have one on my helmet now. It's completely waterproof and pocketable and it puts out a LOT of light, probably on the order of 300 lumens. Given that, I don't think it's really worth screwing around with DIY solutions anymore. I did the whole overvolted MR16 light hooked to a lead-acid cell, DIY HID Trailtech lights, etc, but those days are over.

i believe you, but there are a lot of bad options on ebay too. Are there any vendors you have had good luck with?

What gauge wire are you using? You may be able to reduce the voltage drop by going to a heavier guage wire between the head and the battery pack.

I got my bike light through Amazon, probably much less than the claimed lumens, but still plenty bright and reasonable price. Power is from a pack with 4 18650 cells and runs for almost 4 hours on high:
https://www.amazon.com/Lumen-Bicycle-...dp/B006QQX3C4/

I just got back from a bike trip (in the friggin rain again with 25mph winds, but I really needed to go, my cats were starving) and I took the pack off the bike to recharge the cells and one of the cells are bad, that's the problem. So I just tossed it aside to see if it can be reconditioned and I put a different (but same brand/model) in the charger. I think most of the voltage drop was coming from that 1 cell, I'll have to check it again after they are all charged.

I'm not sure of the gauge of the wires (I threw the packaging away a long time ago), but both(red wire and black wire) are pretty heavy, the black one is solid.
How is the beam?

Are 18650 cells primary or rechargeable?



Thanks for the input from everyone.

Chris

18650 cells are Li-ion rechargeable and put out 3.7v at up to 3400mah now, although 2400 is much more common.

I bought two of them.

Runs 4 hours on strobe and 8.5 hours on low which is great for road riding.

Try measuring the voltage at the battery pack rather than the light -- if the voltage is higher there, then the problem is your long wires.

That said, while I admire your DIY attitude, I have to point out that a single cell 18650 flashlight would probably beat your system in most ways, and can be had with batteries, charger and light for around $30 or maybe less. It would be a lot smaller and more convenient, put out more light (on high), and last longer (on medium, which would still put out about the same amount of light as your system.)

Actually, the Amazon light mentioned recently is an even better choice.

And to answer your question, 18650 is a size, like AA or AAA is rather than a rechargeable or not-rechargeable designation, but I've never seen one that wasn't rechargeable.

Description says

"Battery Configurations: Powered by a rechargeable 8.4V 4400mAh lithium-ion battery pack (4x 18650 Batteries; Battery overcharge protection)"

I did a search and these batteries generally sell for $10 for a 2200mah at 3.7V (standard lithium-ion chemistry voltage) and there are a LOT of 1 star reviews specifically about the batteries and that there are multiple sellers and you don't know which seller you will be working with. Some reviewers are saying they are getting good customer service, some are getting very bad customer service and another complaint is that they are being shipped from China and take over 1 month to arrive.

Where are they getting the 8.4V from? They are describing it as an 8.4V battery pack, not that the unit is stepping up the voltage.
It looks like they are using 2 sets of 2 cells in parallel and the two sets are then wired in series like "=>=>---8.4V where each - is a cell for a 36.96 watt hour battery. But the normal voltage of a lithium ion cell is 3.6-3.7V. Seems kind of flaky.

From a light perspective, it looks like a great alternative and I especially like the Velcro battery pack holder/strap because theft is a huge issue in Philadelphia and it would be easy to just take it in a store with me (like I do with my GPS)

Has anyone ordered this and had it for a while? I certainly don't want to buy a light who's battery pack will fail in a few months and costs more than the whole package to replace (at $10 a cell + shipping).

Chris

TWO YEAR Warranty:
https://www.amazon.com/gp/product/B00..._email_1p_0_ti

That was where I measured the voltage, right at the battery pack. I do think the one cell was bad. The wires are only about 3ft tops.
The Amazon light looks tempting, but there are a LOT of bad reviews all revolving around the batteries. I looked up the batteries and they run around 10 bucks for a 2200 cell, that's $40 worth of batteries in a $28 light. Something has to give, right? I really can't afford to play amazon roulette and get a bad seller (one of the complaints in the review is that this item can come from a number of different sellers, some of whom are giving really bad customer service, some of whom are giving good cs). As we move into spring, the light will become less and less of an issue as it's light until almost 9:00pm at 40 degrees lat (which is where I am) during late spring and early summer.

Chris

I've had good luck with the UltraFire WF-501B. It's simple and it has been reliable for me.

When shopping for a 2nd copy, I looked on eBay and decided to go for a 2nd complete package instead of just a light, because I could use a 2nd charger for work and a few spare cells doesn't hurt.
I got this:

https://www.ebay.com/itm/271032780742...84.m1497.l2649

Yes, the battery pack has 4 cells wired with two parallel sets of two cells in series. The 8.4V is the max. voltage of the charger and is higher than the nominal voltage of the Li Ion cells (2 x 3.7V or 7.4V). I haven't had mine very long yet, but it has been through several charge cycles and is working fine. There was a quality problem with the battery packs about a year ago, incl. some that caught fire due to inadequate control of the charging. I'm hoping the battery quality has improved and most indications are that it has.

Two Cree 5's mounted on my hot rod bike. Adjustable focus heads

Get 3 hours run time on a battery.

Then measure each cell individually, especially while the light is on. They should all be about the same.

Nah, the cells can be had for $4 each from DX (but don't get the more expensive, higher capacity cells -- they're the ones with bad reviews). Though I probably wouldn't suggest making your own pack from these cells -- just buy a premade one. And note that the average review was still four stars. And that said, you could also just make your own pack with six NiMH AA cells if your battery failed. It wouldn't perform quite as good as the stock pack, but it would get pretty close, especially if you avoided high mode and stuck to medium or low. (And even medium mode would be better than most lesser bike lights.)

Well, that's easy -- Amazon will let you see the overall customer satisfaction rating for each vendor, so you pick one that's higher rather than lower. You're still playing the odds, but you're at least making an informed decision.

Nice bike. A few questions about it. What is the white thing that is covering the front brake and protruding out? Is it a whistle of some sort, like one of those deer or dog whistles? What is on the back of the seat? Is it some sort of cage for a bag or something? Lastly, it looks like you can only brake when you are in the down position with your hands on the lower part of the ram handles. Is that the case? I have an old 10 speed from the 70's and it has those ram handlebars, but it has dual brake levers so you can brake from either position. Does riding in such a position hurt your back (the old 10 speed I have is unusable at the moment, I plan on fixing it in the summer, needs tires and new cables). I ride in a fairly upright position leaning forward at about a 45D angle and I find it takes all of the pressure off my back. I can't walk 2 blocks without pain, but I can ride for hours (without back pain).

The brakes are White.

Herbie horn.

Seat bottle holders

No problems using the brakes.

My 70 y\o back is in the condition same as yours. No walking, but can ride all day.


Not me, but The Director of The Houston Cure Cure