View Single Post
  #30  
Old February 8th 18, 09:21 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 6,016
Default Battery Replacement on Lights with Internal Li-Ion Batteries

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.

[...]

--
Regards, Joerg

http://www.analogconsultants.com/
Ads
 

Home - Home - Home - Home - Home