Path: ...!news.mixmin.net!news2.arglkargh.de!news.karotte.org!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
From: Jeff Liebermann <jeffl@cruzio.com>
Newsgroups: rec.bicycles.tech
Subject: Re: bike light optics
Date: Wed, 10 Apr 2024 11:26:11 -0700
Lines: 39
Message-ID: <qukd1jt89r3r9d5tmuqhlp699i0j5e8au0@4ax.com>
References: <uukcfb$3tspr$1@dont-email.me> <jrjPN.617728$Rq2.250265@fx15.ams4> <uumsuu$qiga$3@dont-email.me> <zyDPN.635506$Rq2.626274@fx15.ams4> <uun21g$rv7k$1@dont-email.me> <rxGPN.525218$jO2.46696@fx10.ams4> <uup9ad$1fo65$1@dont-email.me> <0ni91jlfr7qq71svg7panvdr10u6t7n7b2@4ax.com> <uv324b$4jcf$2@dont-email.me> <IteRN.19231549$ee1.7040372@fx16.ams4> <uv5rs5$temf$3@dont-email.me> <yJvRN.444084$Tp2.413276@fx03.ams4> <uv64cj$vua9$1@dont-email.me> <wKwRN.547679$ET2.22255@fx12.ams4>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 8bit
X-Trace: individual.net 4AxU2fB6+tcNNy0gO/DFzAYFfVJT1jEKSYMXKHIX2FvgYFjQcl
Cancel-Lock: sha1:UEZfXboqwM7faapAn75dtDvRHys= sha256:gnj6dWyc0OUrHxpo3mBzvOGEfS+jKiULTYLlZK5ezIs=
User-Agent: ForteAgent/8.00.32.1272
Bytes: 2787

On Wed, 10 Apr 2024 13:46:04 GMT, Roger Merriman <roger@sarlet.com>
wrote:
(chomp)
>I’m told it’s 6 watts at 12 volts which makes sense ie double, but they are
>claiming 12 watts which I’m sure is possible but improbable without
>increasing the drag. Ie power in.

Powering the light from a battery, which is re-charged by a dynamo,
can be viewed as a perpetual motion machine.  Each stage has it's
losses.  From the rider to the light, the overall efficiency is
something like:
  dynamo_efficiency * battery_charge_efficiency *
battery_discharge_efficiency * DC_to_DC_converter_efficiency *
LED_light_efficiency

If I assume that everything listed is 90% efficient, the overall
efficiency is:
  0.9 * 0.9 * 0.9 * 0.9 * 0.9 = 59% efficiency
Including additional losses, such as wind resistance, drag, rolling
resistance, battery aging will just make the efficiency worse.  Note
that I'm ignoring the caloric conversion efficiency of the rider diet
to pedaling power.  Such a charging system is similar to installing a
gasoline generator in a Tesla EV to recharge the Tesla battery while
driving.

>But as Jeff has said hopefully we’ll get some documentation at some point.

Once the company attorneys become involved and inform the marketing
department that the company can be sued for making performance claims
that can't be demonstrated, I would expect to see fewer but better
specifications.



-- 
Jeff Liebermann                 jeffl@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann      AE6KS    831-336-2558