From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp113.iad3a.emailsrvr.com (smtp113.iad3a.emailsrvr.com [173.203.187.113]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id EE28C3CB35 for ; Mon, 5 Jun 2017 14:01:11 -0400 (EDT) Received: from smtp23.relay.iad3a.emailsrvr.com (localhost [127.0.0.1]) by smtp23.relay.iad3a.emailsrvr.com (SMTP Server) with ESMTP id B8FF92514B; Mon, 5 Jun 2017 14:01:11 -0400 (EDT) Received: from app60.wa-webapps.iad3a (relay-webapps.rsapps.net [172.27.255.140]) by smtp23.relay.iad3a.emailsrvr.com (SMTP Server) with ESMTP id 9B0F6252EC; Mon, 5 Jun 2017 14:01:11 -0400 (EDT) X-Sender-Id: dpreed@reed.com Received: from app60.wa-webapps.iad3a (relay-webapps.rsapps.net [172.27.255.140]) by 0.0.0.0:25 (trex/5.7.12); Mon, 05 Jun 2017 14:01:11 -0400 Received: from reed.com (localhost [127.0.0.1]) by app60.wa-webapps.iad3a (Postfix) with ESMTP id 8A5F520054; Mon, 5 Jun 2017 14:01:11 -0400 (EDT) Received: by apps.rackspace.com (Authenticated sender: dpreed@reed.com, from: dpreed@reed.com) with HTTP; Mon, 5 Jun 2017 14:01:11 -0400 (EDT) X-Auth-ID: dpreed@reed.com Date: Mon, 5 Jun 2017 14:01:11 -0400 (EDT) From: dpreed@reed.com To: dpreed@reed.com Cc: "Richard Smith" , "cerowrt-devel@lists.bufferbloat.net" MIME-Version: 1.0 Content-Type: text/plain;charset=UTF-8 Content-Transfer-Encoding: quoted-printable Importance: Normal X-Priority: 3 (Normal) X-Type: plain In-Reply-To: <1496685154.544113991@apps.rackspace.com> References: <2d60e776-2a4f-de66-0d2f-a36568562f96@gmail.com> <1496685154.544113991@apps.rackspace.com> Message-ID: <1496685671.564811498@apps.rackspace.com> X-Mailer: webmail/12.9.1-RC Subject: Re: [Cerowrt-devel] =?utf-8?q?solar_wifi_ap_designs=3F?= X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 05 Jun 2017 18:01:12 -0000 It doesn't jump to mind, but a radio carrying bits near the edge probably w= on't be used near capacity most of the 24 hours it is operating. Just as Ir= idium was designed to quiesce most of its electronics on the dark side of t= he earth, extending its battery life, you can probably assume that a radio = in a tree won't be heavily used most of the hours of a 24 hour cycle. =0A= =0A=0A=0AOn Monday, June 5, 2017 1:52pm, dpreed@reed.com said:=0A=0A> "Deep= discharge" batteries work in LEO satellites for such applications. But the= y=0A> are extraordinarily expensive, because the designs are specialized, a= nd that use=0A> case doesn't have the 2-3 day solar outage problem.=0A> =0A= > You are not going to put a good enough system for an AP up in a tree. May= be on an=0A> antenna mast structure with solid base and guy wires. Roofs an= d ground are better=0A> choices.=0A> =0A> But I would wonder whether redesi= gning the AP itself to be power-conserving would=0A> be the place to start.= They are not designed to be "low power" - they are designed=0A> to be inex= pensive.=0A> =0A> So, for example: why 12V??? No logic needs 12V. Integrate= the battery into the AP=0A> and run it at 3V, eliminating multiple convers= ion losses.=0A> =0A> You can use 12/20 V off the solar panel to charge the = 3V battery system (high=0A> current only while charging).=0A> =0A> Pay lots= of attention to the duty cycle of the radio. If you really expect the=0A> = radio to be on 100% of the time, you may have to power it all the time. Oth= erwise,=0A> minimize uptime. Similarly, the processor need not be on most = of the time if it=0A> is mostly idle while accepting and sending packets fr= om memory. (ARM BIG.little=0A> might be helpful).=0A> =0A> Get rid of Linux= if possible. Linux is not a low-power OS - needs a lot of work in=0A> conf= iguring or rewriting drivers to cut power. (there's a need for an LP Linux,= =0A> but like Desktop Linux, Linus, and his coterie, isn't terribly interes= ted in=0A> fixing his server OS to optimize for non-servers, so "server pow= er saving" is the=0A> only design point for power).=0A> =0A> =0A> =0A> =0A>= On Monday, June 5, 2017 12:01pm, "Richard Smith" sai= d:=0A> =0A>> On 06/04/2017 08:49 PM, Dave Taht wrote:=0A>>> I keep finding = nicely integrated solar/battery/camera/wifi designs=0A>>>=0A>>> https://www= .amazon.com/s/ref=3Dnb_sb_noss_2?url=3Dsearch-alias%3Delectronics&field-key= words=3Dsolar+wifi&rh=3Dn%3A172282%2Ck%3Asolar+wifi=0A>>>=0A>>> But what I = want is merely an solar/battery/AP design well supported by=0A>>> lede... a= nd either the ath9k or ath10k chipset - or mt72 - that I can=0A>>> hang off= a couple trees. I've not worked with solar much in the past=0A>>> years, a= nd picking the right inverter/panel/etc seems like a pita, but=0A>>> perhap= s there are ideas out there?=0A>>=0A>> This is something I was up against c= onstantly when I worked for OLPC.=0A>> There's a big gap for products that = use more power than a cell phone but=0A>> less than an RV or a off-grid cab= in.=0A>>=0A>> For the XO itself we worked around it by designing the front = end of the=0A>> XO to be able to handle the range of output voltages from "= 12V" panels=0A>> (open circuit voltages up to 20V) and to implement an MPPT= algorithim in=0A>> the EC firmware. You can plug up any solar panel with = a Voc of 20V or=0A>> less to an XO-1.5 to XO-4 and it will DTRT.=0A>>=0A>> = Figuring out what to do with the deployment's APs though was always a=0A>> = struggle.=0A>>=0A>> Solutions exist but you need to get a good estimate of = what sort of=0A>> power budget you need. It makes a big difference in what= equipment you=0A>> need.=0A>>=0A>> Unless its a really low power device th= e numbers can get large fast.=0A>>=0A>> My WNDR 3700v2 power supply is rate= d at 12V 2.5A which is a peak of 30W.=0A>>=0A>> Lets assume your average is= 30% of peak. That's 9W. Your 24h energy=0A>> requirement is 216Wh. A re= asonable input to usable efficiency for a PV=0A>> system is 70%. Given ave= rage 5 hour window of full sun you need a PV=0A>> output of at least 62W. = It only goes up from there.=0A>>=0A>> Realistically you need to survive a 2= -3 day period of terrible solar=0A>> output. So your storage requirements = should be at least 2-3x that.=0A>> When you do get sun again you need exces= s PV capacity to be able to=0A>> recharge your batteries. You would probab= ly need a PV output in the=0A>> 100W-150W range to make a system you could = count on to have 100%=0A>> availability 24/7.=0A>>=0A>> That's going to be = a pretty big chunk of hardware up in a tree.=0A>>=0A>> If the average power= draw is more in the 3W or 1W range then things look=0A>> a lot better. T= hat starts to get down into the 40 and 20W range.=0A>>=0A>>> so am I the on= ly one left that likes edison batteries? you don't need=0A>>> a charge cont= roller... they last for a hundred years....=0A>>> _________________________= ______________________=0A>>=0A>> I've never used this battery type but it l= ooks like the resistant to=0A>> overcharge assumes you replace the electrol= yte. All the cells I've=0A>> looked at on a few sites seem to be flooded w= hich means maintenance.=0A>> Are there sealed maintenance free versions?=0A= >>=0A>> For discharge nominal is 1.2V but charging is listed as ~1.6V/cell = so=0A>> you are going to need 16V to charge. I don't really see how you ca= n=0A>> build a workable system with out some sort of setup that can isolate= =0A>> your 12V loads from a 16V charge.=0A>>=0A>> Perhaps undercharge them = at a lower voltage and live with the capacity=0A>> loss?=0A>>=0A>> --=0A>> = Richard A. Smith=0A>> _______________________________________________=0A>> = Cerowrt-devel mailing list=0A>> Cerowrt-devel@lists.bufferbloat.net=0A>> ht= tps://lists.bufferbloat.net/listinfo/cerowrt-devel=0A>>=0A> =0A> =0A> _____= __________________________________________=0A> Cerowrt-devel mailing list= =0A> Cerowrt-devel@lists.bufferbloat.net=0A> https://lists.bufferbloat.net/= listinfo/cerowrt-devel=0A> =0A