From owner-freebsd-questions@FreeBSD.ORG Sat Nov 29 09:10:39 2014 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 02686613 for ; Sat, 29 Nov 2014 09:10:39 +0000 (UTC) Received: from agora.rdrop.com (agora.rdrop.com [IPv6:2607:f678:1010::34]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id B5726DBB for ; Sat, 29 Nov 2014 09:10:38 +0000 (UTC) Received: from agora.rdrop.com (66@localhost [127.0.0.1]) by agora.rdrop.com (8.13.1/8.12.7) with ESMTP id sAT9AYHJ024676 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Sat, 29 Nov 2014 01:10:35 -0800 (PST) (envelope-from perryh@pluto.rain.com) Received: (from uucp@localhost) by agora.rdrop.com (8.13.1/8.14.2/Submit) with UUCP id sAT9AY24024675; Sat, 29 Nov 2014 01:10:34 -0800 (PST) (envelope-from perryh@pluto.rain.com) Received: from fbsd81 by pluto.rain.com (4.1/SMI-4.1-pluto-M2060407) id AA21011; Sat, 29 Nov 14 00:49:12 PST Date: Sat, 29 Nov 2014 00:49:07 -0800 From: perryh@pluto.rain.com (Perry Hutchison) To: erichsfreebsdlist@alogt.com Subject: Re: OT: UPS for FreeBSD Message-Id: <54798883.saa13h6lE6rPwZCf%perryh@pluto.rain.com> References: <54777AB1.9010800@bluerosetech.com> <54779629.302@bluerosetech.com> <5478BD4F.7020306@yahoo.com> <5478BEE6.30308@bluerosetech.com> <5478CC08.9090307@yahoo.com> <20141128204722.561f948e@archlinux> <5478F16A.80605@yahoo.com> <54791d3a.w/pI0kak03d+3nKC%perryh@pluto.rain.com> <20141129113405.3d1bd1d6@X220.alogt.com> In-Reply-To: <20141129113405.3d1bd1d6@X220.alogt.com> User-Agent: nail 11.25 7/29/05 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: kudzu@tenebras.com, freebsd-questions@freebsd.org X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 29 Nov 2014 09:10:39 -0000 Erich Dollansky wrote: > As switching voltage regulators use a few hundred volts, > it is a bit difficult to match this with a battery. Depends on how many cells one is willing to string together in series. IIUC the battery in a Toyota Prius supplies a few hundred volts. However, there is no intrinsic reason why a switching regulator _has to_ take a few hundred volts as input. Those under discussion here are set up that way because that is what is easily and cheaply available: 120VAC ==> full-wave rectifier ==> ~300 VDC ==> switching regulator | | 12VDC <--+ | | 5VDC <------+ (That is typical for North America; in Europe the AC would be ~240V and the DC therefore ~600V.) To integrate a UPS with the PSU, one would instead build something along the lines of: multitapped 120VAC ==> step-down ==> 6VAC ==> full-wave ==> ~15VDC ==> battery1 transformer rectifier | +---> 3VAC ==> full-wave ==> ~7.5VDC ==> battery2 rectifier battery1 ==> regulator ==> 12VDC battery2 ==> regulator ==> 5VDC IOW the computer runs off the batteries, which are charged by the stepped-down but unregulated (or minimally-regulated) line voltage. There is nothing the least bit new about this -- the telephone industry was doing it in the mid 20th century. They installed enough battery capacity for their system to run on battery power alone for however long it would take to get their standby generators started up (or for at least a few days in smaller offices that did not have standby generators).