18650 Batteries and Why Dynamos Can't Competer
 

A great many bicycle lights use 18650 Li-Ion batteries. At Fry's they
are now selling Tenergy 18650 protected cells for $4 each, these:
http://www.all-battery.com/li-ion1865037v2600mahrechargeablebatterieswithpcb-1.aspx.
Of course they quickly sold out but I got three of them.

If Fry's is retailing these for $4 then the light manufacturers are
probably paying less then $2 each. Six batteries, a Cree LED, optics,
PWM controller, switch, enclosure and charger probably have a bill of
materials of around $25. So while the Magicshine lights seem very cheap
at $80, it's understandable why there are so many Magicshine clones
selling for $30-40. There's still big bucks to be made when you can sell
direct and accept margins of less than 50%. A dynamo system with a good
hub dynamo and front light is going to have a retail cost of at least $200.

18650 Batteries and Why Dynamos Can't Competer
 

On Wed, 04 Mar 2015 16:54:08 -0800, sms
wrote:

A great many bicycle lights use 18650 Li-Ion batteries. At Fry's they
are now selling Tenergy 18650 protected cells for $4 each, these:
http://www.all-battery.com/li-ion1865037v2600mahrechargeablebatterieswithpcb-1.aspx.
Of course they quickly sold out but I got three of them.

Tenergy 18650 battery came out in the middle of the pack on the Candle
Power Forums 2011 and 2012 tests.
http://www.candlepowerforums.com/vb/showthread.php?257543-LiIon-18650-battery-comparison
Even the electric cigarette people like them:
http://www.e-cigarette-forum.com/forum/battery-mods/235469-best-18650-battery-2.html#post4595302

$4/ea is a very good price. The problem is that Tenergy seems to be
changing their supplier and packaging often enough that I can't
identify the real cells from any counterfeits:
https://www.google.com/search?q=Tenergy+18650&tbm=isch

If Fry's is retailing these for $4 then the light manufacturers are
probably paying less then $2 each. Six batteries, a Cree LED, optics,
PWM controller, switch, enclosure and charger probably have a bill of
materials of around $25.

6 batteries? Are you thinking megalumens or designing some for Joerg?
Using the 2012 test curves, one Tenergy 18650 battery can probably
deliver 1.8A-hrs at an average of 3.4V or about 6 watt-hrs. Therefore,
the usual 4 watt (or 2x2 watt) LED's are going to last
6/4 = 1.5 hrs on a single cell. To get battery life that's actually
usable, I would like to see about 4 hrs at full brightness, which will
require 4/1.5 = 2.7 = 3 cells. 6 cells should last 6*1.5 = 9 hrs,
which might be overkill. Anyway, you can cut back on the number of
18650 cells and still have a usable light. Or, you could use a bigger
LED, and get more brightness over the same period.

Add a balance charger, state of charge indicator, mounting bracket,
compliance engineering, packaging, promotional literature,
advertising, endorsements, etc. If there's any time or money left,
maybe some testing.

So while the Magicshine lights seem very cheap
at $80, it's understandable why there are so many Magicshine clones
selling for $30-40.

Factory rejects? Stolen from the factory? Government subsidies?

There's still big bucks to be made when you can sell
direct and accept margins of less than 50%. A dynamo system with a good
hub dynamo and front light is going to have a retail cost of at least $200.

Well, if you're going to compare dynamo and battery lights, methinks
it might be useful to compare equal brightness lights. That would
mean lower power LED's and fewer 18650 batteries. Exactly how much
smaller or fewer, I don't know.

Incidentally, Winfield Hill just posted to sci.electronics.design a
free sample from his new book, Art of Engineering III. It's on
voltage regulators and includes quite a bit of stuff that methinks
will be useful in the design of a dynamo regulator and LED light
driver.
https://www.dropbox.com/s/r8gu22ficfac3pz/AoE-III_ch-9_109pgs.pdf?dl=0

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

18650 Batteries and Why Dynamos Can't Competer
 

Why mess with weeny batteries ?

I use a 6 volt SLA battery with a circuit that reduces 6 V to 4.5 V.

It powers 2 500 lumen headlights and a 300 lumen tail light.

I charge it about every 3 months.

Andy

18650 Batteries and Why Dynamos Can't Competer
 

On Thursday, March 5, 2015 at 1:54:10 AM UTC+1, sms wrote:
A great many bicycle lights use 18650 Li-Ion batteries. At Fry's they
are now selling Tenergy 18650 protected cells for $4 each, these:
http://www.all-battery.com/li-ion1865037v2600mahrechargeablebatterieswithpcb-1.aspx.
Of course they quickly sold out but I got three of them.

If Fry's is retailing these for $4 then the light manufacturers are
probably paying less then $2 each. Six batteries, a Cree LED, optics,
PWM controller, switch, enclosure and charger probably have a bill of
materials of around $25. So while the Magicshine lights seem very cheap
at $80, it's understandable why there are so many Magicshine clones
selling for $30-40. There's still big bucks to be made when you can sell
direct and accept margins of less than 50%. A dynamo system with a good
hub dynamo and front light is going to have a retail cost of at least $200.

Compete in what way? Price wise?

Lou

18650 Batteries and Why Dynamos Can't Competer
 

On Wed, 4 Mar 2015 19:20:31 -0800 (PST), Andy K
wrote:

Why mess with weeny batteries ?

Weight.
http://en.wikipedia.org/wiki/Energy_density
Li-Ion will deliver about 0.5 MJ/kg while a lead acide battery will do
only 0.17 MJ/kg. For the same energy, you'll need to carry 3 times
the weight.

I use a 6 volt SLA battery with a circuit that reduces 6 V to 4.5 V.
It powers 2 500 lumen headlights and a 300 lumen tail light.
I charge it about every 3 months.

Let's do the math. You have 2x500 + 300 lumens = 1300 lumens. At 100
lumens/watt, that's 13 watts of power. You didn't specify the size of
your SLA battery or how long you run the light every 3 months. A
common 6v SLA battery is rated at 10 A-hrs. Assuming you don't want
to destroy the battery, you can get about half of that out of the
battery or 5 A-hrs or 6*5 = 30 watt-hrs. At a 13 watt drain, that's
2.3 hrs of operation (assuming 100% conversion efficiency in your
6v-4.5v DC-DC converter and no 5%/month self discharge). Assuming
you ride 5 days per week for 3 months or roughly:
5 days * 12 weeks = 60 days
you get to use the light for:
2.3 hrs / 60 days * 60 min/hr = 2.3 minutes/day operation
That seems unlikely with only a 6v 10 A-hr battery. I would suspect
your battery is larger. Ummm.... how large or how many minutes per
day do you use it?

Incidentally, a 6v 10A-hr SLA weighs about 2.7 kg (6 lbs), which you
get to drag around for 3 months so you have have 2.3 minutes per day
of light.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

18650 Batteries and Why Dynamos Can't Competer
 

http://goo.gl/UFycJE

18650 Batteries and Why Dynamos Can't Competer
 

AE6KS -


'Incidentally, a 6v 10A-hr SLA weighs about 2.7 kg (6 lbs), which you
get to drag around for 3 months so you have have 2.3 minutes per day
of light.'

not much to the dyno squad ..

the lion weighs ?

the 5 pounds is relative to the other 'extra' weight you're hauling

unless ura compulsive weenie retentive

one more question...is battery use age cawsing you pain relative to mercury poisoning in the ocean ?

I wuz doing kayak touring hull design visavee skin on frame hulls which is oranges and milkweed but uno the tillerman insists...

My yak is a cargo yak with sophisticated and expensive hull design sumpthing like 1 mph less touring speed than the thin light FAST FAST FAST design that only 'experts' paddle.

My suggestions received considerable umbridge.

Gazing over that I feel again serious thoughts of 'advanced tech snottery' vs effective tech applications...

just saying uno...not casting dispersions on the movement.

18650 Batteries and Why Dynamos Can't Competer
 

The point is that I am not changing batteries out every 2 days like 18650 and aaa battery users are.

18650 Batteries and Why Dynamos Can't Competer
 

On Thu, 5 Mar 2015 09:31:28 -0800 (PST), Andy K
wrote:

The point is that I am not changing batteries out every 2 days like 18650 and aaa battery users are.

You didn't answer my question. What's the rating on your 6v SLA
battery (amp-hrs)? How many hours does it it run in your 3 month
cycle? Efficient DC-to-DC switching regulator or inefficient LDO
linear regulator to get from 6V to 4.5V (or just 2 diodes in series)?

I don't believe that you can do a 3 month charge cycle with a 13 watt
lighting system and a realistic number of hours of operation per day.
That's why I did the calculations errr... guesstimations.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

18650 Batteries and Why Dynamos Can't Competer
 

Jeffi, try to not badger the posters