From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp89.iad3a.emailsrvr.com (smtp89.iad3a.emailsrvr.com [173.203.187.89]) (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 F108A3B2A4 for ; Mon, 5 Jun 2017 13:52:34 -0400 (EDT) Received: from smtp28.relay.iad3a.emailsrvr.com (localhost [127.0.0.1]) by smtp28.relay.iad3a.emailsrvr.com (SMTP Server) with ESMTP id C78295425; Mon, 5 Jun 2017 13:52:34 -0400 (EDT) Received: from app24.wa-webapps.iad3a (relay-webapps.rsapps.net [172.27.255.140]) by smtp28.relay.iad3a.emailsrvr.com (SMTP Server) with ESMTP id 9797153C0; Mon, 5 Jun 2017 13:52:34 -0400 (EDT) X-Sender-Id: dpreed@reed.com Received: from app24.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 13:52:34 -0400 Received: from reed.com (localhost [127.0.0.1]) by app24.wa-webapps.iad3a (Postfix) with ESMTP id 853C3C05EB; Mon, 5 Jun 2017 13:52:34 -0400 (EDT) Received: by apps.rackspace.com (Authenticated sender: dpreed@reed.com, from: dpreed@reed.com) with HTTP; Mon, 5 Jun 2017 13:52:34 -0400 (EDT) X-Auth-ID: dpreed@reed.com Date: Mon, 5 Jun 2017 13:52:34 -0400 (EDT) From: dpreed@reed.com To: "Richard Smith" Cc: "Dave Taht" , "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: <2d60e776-2a4f-de66-0d2f-a36568562f96@gmail.com> References: <2d60e776-2a4f-de66-0d2f-a36568562f96@gmail.com> Message-ID: <1496685154.544113991@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 17:52:35 -0000 "Deep discharge" batteries work in LEO satellites for such applications. Bu= t they are extraordinarily expensive, because the designs are specialized, = and that use case doesn't have the 2-3 day solar outage problem.=0A=0AYou a= re not going to put a good enough system for an AP up in a tree. Maybe on a= n antenna mast structure with solid base and guy wires. Roofs and ground ar= e better choices.=0A=0ABut I would wonder whether redesigning the AP itself= to be power-conserving would be the place to start. They are not designed = to be "low power" - they are designed to be inexpensive.=0A=0ASo, for examp= le: why 12V??? No logic needs 12V. Integrate the battery into the AP and ru= n it at 3V, eliminating multiple conversion losses.=0A=0AYou can use 12/20 = V off the solar panel to charge the 3V battery system (high current only wh= ile charging).=0A=0APay lots of attention to the duty cycle of the radio. I= f you really expect the radio to be on 100% of the time, you may have to po= wer it all the time. Otherwise, minimize uptime. Similarly, the processor = need not be on most of the time if it is mostly idle while accepting and se= nding packets from memory. (ARM BIG.little might be helpful).=0A=0AGet rid = of Linux if possible. Linux is not a low-power OS - needs a lot of work in = configuring or rewriting drivers to cut power. (there's a need for an LP Li= nux, but like Desktop Linux, Linus, and his coterie, isn't terribly interes= ted in fixing his server OS to optimize for non-servers, so "server power s= aving" is the only design point for power).=0A=0A=0A=0A=0AOn Monday, June 5= , 2017 12:01pm, "Richard Smith" said:=0A=0A> On 06/04= /2017 08:49 PM, Dave Taht wrote:=0A>> I keep finding nicely integrated sola= r/battery/camera/wifi designs=0A>>=0A>> https://www.amazon.com/s/ref=3Dnb_s= b_noss_2?url=3Dsearch-alias%3Delectronics&field-keywords=3Dsolar+wifi&rh=3D= n%3A172282%2Ck%3Asolar+wifi=0A>>=0A>> But what I want is merely an solar/ba= ttery/AP design well supported by=0A>> lede... and either the ath9k or ath1= 0k chipset - or mt72 - that I can=0A>> hang off a couple trees. I've not wo= rked with solar much in the past=0A>> years, and picking the right inverter= /panel/etc seems like a pita, but=0A>> perhaps there are ideas out there?= =0A> =0A> This is something I was up against constantly when I worked for O= LPC.=0A> There's a big gap for products that use more power than a cell pho= ne but=0A> less than an RV or a off-grid cabin.=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 vol= tages 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 depl= oyment'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 the numbers can get large fast.=0A> =0A> My = WNDR 3700v2 power supply is rated 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 reasonable input to usable efficiency for a P= V=0A> system is 70%. Given average 5 hour window of full sun you need a PV= =0A> output of at least 62W. It only goes up from there.=0A> =0A> Realisti= cally you need to survive a 2-3 day period of terrible solar=0A> output. S= o your storage requirements should be at least 2-3x that.=0A> When you do g= et sun again you need excess PV capacity to be able to=0A> recharge your ba= tteries. You would probably 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 lo= ok=0A> a lot better. That starts to get down into the 40 and 20W range.= =0A> =0A>> so am I the only one left that likes edison batteries? you don't= need=0A>> a charge controller... they last for a hundred years....=0A>> __= _____________________________________________=0A> =0A> I've never used this= battery type but it looks like the resistant to=0A> overcharge assumes you= replace the electrolyte. All the cells I've=0A> looked at on a few sites = seem to be flooded which means maintenance.=0A> Are there sealed maintenanc= e free versions?=0A> =0A> For discharge nominal is 1.2V but charging is lis= ted as ~1.6V/cell so=0A> you are going to need 16V to charge. I don't real= ly see how you can=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 und= ercharge 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.ne= t=0A> https://lists.bufferbloat.net/listinfo/cerowrt-devel=0A> =0A