From owner-freebsd-questions@FreeBSD.ORG Mon Dec 1 03:14:07 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 C5035E41 for ; Mon, 1 Dec 2014 03:14:07 +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 83339B6A for ; Mon, 1 Dec 2014 03:14:07 +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 sB13E16j087337 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Sun, 30 Nov 2014 19:14:02 -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 sB13E13q087336; Sun, 30 Nov 2014 19:14:01 -0800 (PST) (envelope-from perryh@pluto.rain.com) Received: from fbsd81 by pluto.rain.com (4.1/SMI-4.1-pluto-M2060407) id AA00902; Sun, 30 Nov 14 18:43:09 PST Date: Sun, 30 Nov 2014 18:43:09 -0800 From: perryh@pluto.rain.com (Perry Hutchison) To: erichsfreebsdlist@alogt.com Subject: Re: OT: UPS for FreeBSD Message-Id: <547bd5bd.dKE49fHIj28ERZyT%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> <54798883.saa13h6lE6rPwZCf%perryh@pluto.rain.com> <20141130212746.6d5eaf1f@X220.alogt.com> In-Reply-To: <20141130212746.6d5eaf1f@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: Mon, 01 Dec 2014 03:14:07 -0000 Erich Dollansky wrote: > On Sat, 29 Nov 2014 00:49:07 -0800 > perryh@pluto.rain.com (Perry Hutchison) wrote: > > 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 > > How much energy is then wasted? In the transformer and rectifier, very little: both are highly efficient. The battery will incur charge/discharge losses, but we would have to contend with those in any UPS, regardless of how the batteries are charged or how their energy is delivered to the load. That leaves the regulators. I'm minimizing those losses by providing a separate battery and regulator for each required output voltage, so as to minimize the IV loss in the regulator. If you prefer the (IMO questionable) relative simplicity of using a single (multi-output) regulator, you can certainly use an 18- or 24-volt battery and run the regulator(s) off of that to deliver 12VDC and 5VDC (or whatever voltages are needed). The point is that it is certainly simpler, and likely more efficient, to deliver the DC battery power to the DC load by DC -> DC regulation than by inverting to 120 or 240VAC only to have the PC's PSU convert the AC right back to DC for the load -- which how external UPS operate.