Probably due to incorrect ground. The temptation to use the frame as ground must be resisted with LED lamps driven by a dyno. The AC to DC conversion only works correctly when both leads from the dyno hub are connected directly to the LED lamp.

(If the frame is used as ground for the dyno hub and the LED lamp then the AC to DC conversion is not a full wave rectification, rather it is half wave and less than 1/2 the overall power. Combine that with a supercap standby circuit that must be charged up before the LED is turned on means it takes a few blocks to charge up the system.)

I just bought a Lumina 750, and the biggest problem for me is how the light mounts to the mounting bracket.

The mount has a slider rail for the light, and there is a plastic tab at the end with two teeth. The light has two holes where the teeth are supposed to click into to secure it so it doesn't go sliding back off the rails. Problem is, the tab has no spring under it, and my tab kind of droops down so the teeth never engage firmly. And this is after removing it ONCE for the initial charge.

I can imagine that even if it clicks in ok, a few dozen times of pressing down on the tab to release the light for charging, locking up, etc. puts pressure on the plastic and it will start drooping down on its own.

Great light, terrible bracket mount design. Needs some opposite force, like a spring, to keep the tab up and tight against the light.

I thought this thread would be all about $30 Ebay LiPO/Cree combinations, that's all I use. 4 hours off 2 packs and bright as hell 2000 Lums. Is there some issue with these lights? Why is everyone using dynamos, I thought they went out of fashion decades ago due to the drag on performance? I will investigate this, fascinating.

Very happy
 

with my sigmasport lights. A Buster 600 on the front, Cuberider II on the left rear seat stay. The Buster is usb rechargeable, with three brightness modes for night headlight and one flashing for daytime. The Cuberider is AAA.

My commute is 9 to 30 miles, depending on route, and the usb rechargeable takes it fine. When I get to work I plug it in and it's good to go when I head home. I justbswitched out the batteries in the rear light after about 4 months (I run it in the daylight as well).

It's hard not to be fascinated with the idea of it, isn't it? The drag is much less now than it was decades ago - a good dynamo is more efficient, the lights are brighter and more efficient.

What's stopped me so far: the setup is more expensive than the Cree LED lights that work great for me, I take the lights off for half the year on one bike at least, and I begrudge even 4-6 watts. And as far as I know, they still aren't as bright as the battery lights. But still, on the commuter workhorse it's a tempting choice.

My headlight is wrenched on with hose clamps, so I don't bother to take it off in the summer, but over the last few months I've turned it on only maybe 2-3 times, and haven't charged the battery. Once we leave daylight savings I'll be riding in the dark every morning and I'll swap&recharge my 18650 headlight battery approx. weekly (I have two batteries, light takes one, batteries take turns each week being used vs backup)


I use my red blinky (cygolite hotshot) full time, and pop it on the usb to recharge maybe monthly? I don't even know how often, and can't tell a difference from recharging it, just sometimes I think 'it's been quite a while, this thing must need recharging by now'.

don't forget a backup light. you never know when your primary light is gonna have an issue. maybe never, but maybe 10 miles from home on a dark unlit road on a rainy or snowy night :/

Yep, mine is a cheap Ultrafire that lives in my commuting pack that time of year. It's not great, but in a pinch any light is better than none. Another point in favor of the dynamo system - personally I wouldn't carry a backup light if I had a dynamo.

Yes I researched them, dynamos in the hub, very clever. I won't get one either as I don't do night rides often enough to warrant but want a great boon for the commuter and traveler. You would want to spend the big bucks and get the one with minimal drag in daylight hours though. I'll keep an eye of this for the future.

my first post, LOL. I am currently using the RAVEMEN PR900 for headlight. It has two leds, one for low beam one for high beam, just like the car's light. A great design which I didn't find in other lights. Also, it has an display to show the remaining runtime which is quite useful to me too.

I've used a few of the cheapo CREE lights, and they do the job... for a while. The battery pack on one wore out in about a year, and a buddy's died after a rainstorm. If they had been expensive lights, I might have been upset, but we got our $30 worth out of them.

Sometimes it's not the light that has the issue. I still have those times when I realized I didn't recharge one of my lights and am glad for the backup.

I read here on BF the suggestion to carry a backup light, so I did for a while. My thinking is that my dynamo-powered headlight could fail, leaving me without a headlight. I try not to carry anything I'm unlikely to need. I don't carry spare spokes or spoke wrenches because while I have broken spokes on the road, it happens infrequently enough not to justify the trouble. And when it happens, I can deal with it. I can also deal with riding with no headlight if I have to. I've been riding with dynamo-powered lights for over three years now, and the failure rate of my systems is low enough to show me that I don't need a backup headlight. In three and a half years, I have had two failures: 1. one wire came out of the tail light. 2. While my bike was locked in public, a vandal tried to steal my headlight and failed. He bent the mounting bracket. The light still worked. After I got home, I bent the bracket back into the original shape. This really shouldn't count as a failure. So my headlight has failed zero times in three and a half years.

I cannot perceive the drag the hub creates. If I get home tired from the effort of my ride, I cannot rightfully claim that without the hub, I wouldn't be tired.

Thanks for the info, I'll see how I can waterproof the cells, perhaps little Ziploc sandwich bags before I slip them in the black case? Back in 02,03 I spend hundreds on a vista-lite system and found that the NiMH packs died of old age long before I ever got my monies worth. For someone who only rides in the dark every month or two the cheapos probably make more sense.

They make a lot of sense for someone who rides every day as well. With a $20 light, what does it matter if the battery shorts out? By another light and it comes with a battery. It also makes sense from the standpoint of having more than one light source. Not just for back up but also for utility. Multiple light sources make you stand out more and, at $20 per light, having two or three lights (a light on the helmet is extremely useful) doesn't break the bank.

Well I don't use them everyday so I can't comment on the longevity of the battery packs, I will say this though, You have to be careful mix and matching battery packs now, I have two $20 sets I've been using for a few years and recently bought a third, that looked identical in every respect, but the battery was double the voltage, 8-volts. Without a thought I hooked it up to a 4-volt light and blew it. A silly mistake, I should have checked the fine print. Here is the unit, though I won mine at auction for only $12 delivered :)

Waterproof 5000LM Cree XM L T6 LED Headlamp Head Front Bicycle Lamp Bike Light | eBay

Yeah, IMO a dyno is reliable enough that you don't need backup. I put a shymano hub dyno on my bike in October 2012 and I continue to use it problem-free nearly every day. I keep it turned on pretty-much 24x7 as I think enhanced visibility in shade/shadows might give me a wider berth on the road - anything to draw attention and wake up the day dreaming drivers.

We've ridden for years with Dynamo's (some hub, some bottle) and only one instance I can remember about 5 or so years ago when a wire came loose. They're always on the bikes and always ready whenever needed. I've never known anyone in Netherlands or elsewhere to carry a back-up.

OTOH, forgetting to charge batteries? Or forgetting to find and take a light?