On Thursday, February 8, 2018 at 12:21:15 PM UTC-8, Joerg wrote:
On 2018-02-06 20:48, Jeff Liebermann wrote:
On Tue, 6 Feb 2018 10:52:50 -0800, sms
wrote:


[...]


It's a 2 cell 18650 pack with the batteries in parallel, and a
protection circuit board shared between the two cells. The cells are
allegedly 2800mAH, for a total of 5600mAH.

Seems rather high.


Probably a Chinese spec :-)

Just like with lights where there are lumens and then there are Chilumens..


... Note that batteries are tested at a 0.2C
discharge, which yields larger numbers than the usual headlight
discharge rate. The Lezyne Deca 1500XXL claims 1500 lumens, which
also seems a bit high. Assuming 120 lumens/watt at a nominal
3.7V/battery, that's:
1500 / 120 / 3.7 = 3.4A
to run the headlight at full brightness, or 1.7A per cell.
Meanwhile, the cell capacity is tested at:
0.2 * 2800 = 0.56A


Classic American answer: Then you need a bigger battery. On my road bike
I use eight 18650 cells, four in parallel and two of those packs in
series so the current on the cable to the front light doesn't exceed 1A,
at least not by much.

My MTB has to make do with four cells but except for short bursts on
city streets or fast county roads I drop that down from 8W to 3W or
sometimes even 1.5W in front.

I ride all roads in car traffic with lights, day and night, and then
usually at full bore. Bike paths sans DRL, singletrack with just the
front light lit so dirt bikers see me.

Get a low-watt blinker for daytime if you need a DRL. It's more conspicuous than a fixed beam, depending on where you are riding. I only use a DRL during morning hours, rainstorms or overcast (sometimes). I use a little Nashbar flasher, which is pretty average for riders around here. My rain gear is high-viz, and I tend to avoid all-black like some of my more fashionable cohorts. In daylight, I see rider jerseys long before lights except under rare circumstances.

I'm about to ride home, and if (after climbing out of the parking garage) I decide to ride home on the frustrating cycle path, I will encounter endless dopes with 1000 lumen lights pointed straight at me. Oddly, because of the alignment of the cycletrack, I will not be able to determine whether they are on-coming bicycles in the side-by-side two-way bike lane or cars out on the road. The brighter the light, the more it will look like a car -- and not a bike that will pass me within five inches. One day, I will have a head-on if I ride that path enough.

A beam with cut-off and lower intensity would be much more noticeable as a bike and would not blind me. A 1 watt flasher would make it even more recognizable. One can justify a bright, less-shaped light away from other riders, but blasting the retina burners around other cyclists is unconscionable.

-- Jay Beattie.