At the risk of sounding sarcastic (and I assure this is not my intent) .. to allow a DC appliance to wait and simply turn on when when necessary and not waste power when it is off would take a battery .. internal or external to the appliance.
Something has to keep the appliance powered. The best we can do is minimize the idle power consumption. "Super capacitors" can provide some degree of backup for very low-power needs (micro-watts), but they too will go dead over time if not used, or when given a long-term power draw without being recharged (sounds like a battery again .. no?). Dan --- On Thu, 9/1/11, Darryl Thayer <daryl_so...@yahoo.com> wrote: From: Darryl Thayer <daryl_so...@yahoo.com> Subject: Re: [RE-wrenches] unique battery bank design question To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org> Date: Thursday, September 1, 2011, 5:01 PM I am both interested in the idle power, and the operating efficiency This often comes up, but what does it require to allow a DC appliance to wait and simply turn on when when necessary and not waste power when it is off? Darryl From: Exeltech <exelt...@yahoo.com> To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Sent: Thursday, September 1, 2011 3:30 PM Subject: Re: [RE-wrenches] unique battery bank design question Hi Jason, Well designed off-the-shelf converters can achieve 90% efficiency, and as you mention, this will vary a bit depending on the rated output current of the converter vs. the actual load current. I've designed and built 24V @ 25A to 12V @ 50A converters for my own use that are in the 95% realm. Your mileage may vary. Dan --- On Thu, 9/1/11, Jason Szumlanski <ja...@fafcosolar.com> wrote: From: Jason Szumlanski <ja...@fafcosolar.com> Subject: Re: [RE-wrenches] unique battery bank design question To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org> Date: Thursday, September 1, 2011, 3:07 PM Dan, What kind of efficiency level (%) can you get out of a DC-DC supply on a small load, say <5A @ 12V with a 48V->12V converter? Is the efficiency level highly variable depending on load as a percentage of the converter’s maximum capacity, or is it pretty constant? I run into this once in a while, so this piece of information would help me make some better decisions. Thanks, Jason Szumlanski Fafco Solar _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings:http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org -----Inline Attachment Follows----- _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
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