supercapacitors
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From: Fabian on 17 Aug 2006 17:53 default wrote: > On 16 Aug 2006 09:00:36 -0700, "tschoepflin(a)gmail.com" > <tschoepflin(a)gmail.com> wrote: > > >Does anyone have experience with supercapacitors? What's the best way > >to learn more about them and what they're useful for? Any good web > >links with design examples? > > > >We have a 1 kW transmitter for ultrasound that uses 12 electrolytic > >capacitors (2200uF each) in a bank, for 26.4 mF total capacitance. The > >ESR is very low so our system responds very well when transmitting > >pings (lengths ranging 0.1-1.0 ms). The caps are buffering a 48V power > >rail. I've thought about trying to scale the power rail down to 12 V > >and beefing up the transformer by a factor of 4. > > > >Has anyone used a supercapacitor in a transmitter? > >Thanks for the help. > >-Todd > > > Check out Maxwell Technologies they make a super cap that is a cross > between a lead acid battery and high capacity capacitor - very low ESR > and can deliver 100's of amps > > http://www.maxwell.com/ultracapacitors/index.html > > > > ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- > http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups > ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- I haven't used them in a transmitter, but in a special embedded system with very good results. It was a mission critical system powered from 24V DC which drawed over 1A continuous. The system had to operate 24/7 under poor power conditions, with very frequent power sags and outages. In order to guarantee an orderly shutdown in case of a long term power failure, I need to guarantee 15 seconds of backup power, but given the hostile environment, relatively high temperature and maintainance free requeriments, batteries should be avoided. The solution was to use a bank of "ultracapacitors" (that's the name Epcos give them) in series connection. Six cells of 10[F] 2,3[V] gave us an equivalent capacitance of 1.66[F] at 13,8 [V]. This bank was charged from the 24[V] input by a DC/DC switchmode power supply while a secondary DC/DC converter generated the main 5[V] supply from the 13.8[V] rail of the capacitor bank. This way, the 5 [V] can sustain 1 [A] load current over 15 seconds after a power failure, enough for a safe shutdown. Several hundreds of these systems are still working after several years of operation. At design time, the cells employed (10[F]/2,3[V]) were the the smallest available, both in size and capacity, but there are some real monsters. You can take a look at Epcos ultracapacitor web page: http://www.epcos.com/web/generator/Web/Sections/ProductCatalog/Capacitors/Ultracapacitors/Page,templateId=render,locale=en.html Kind regards, Fabian.//
From: Terry Given on 17 Aug 2006 19:47 Fabian wrote: > default wrote: > > >>On 16 Aug 2006 09:00:36 -0700, "tschoepflin(a)gmail.com" >><tschoepflin(a)gmail.com> wrote: >> >> >>>Does anyone have experience with supercapacitors? What's the best way >>>to learn more about them and what they're useful for? Any good web >>>links with design examples? >>> >>>We have a 1 kW transmitter for ultrasound that uses 12 electrolytic >>>capacitors (2200uF each) in a bank, for 26.4 mF total capacitance. The >>>ESR is very low so our system responds very well when transmitting >>>pings (lengths ranging 0.1-1.0 ms). The caps are buffering a 48V power >>>rail. I've thought about trying to scale the power rail down to 12 V >>>and beefing up the transformer by a factor of 4. >>> >>>Has anyone used a supercapacitor in a transmitter? >>>Thanks for the help. >>>-Todd >> >> >>Check out Maxwell Technologies they make a super cap that is a cross >>between a lead acid battery and high capacity capacitor - very low ESR >>and can deliver 100's of amps >> >>http://www.maxwell.com/ultracapacitors/index.html >> >> >> >>----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- >>http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups >>----= East and West-Coast Server Farms - Total Privacy via Encryption =---- > > > I haven't used them in a transmitter, but in a special embedded system > with very good results. It was a mission critical system powered from > 24V DC which drawed over 1A continuous. The system had to operate 24/7 > under poor power conditions, with very > frequent power sags and outages. > In order to guarantee an orderly shutdown in case of a long term power > failure, I need to guarantee 15 seconds of backup power, but given the > hostile environment, relatively high temperature and maintainance free > requeriments, batteries should be avoided. > > The solution was to use a bank of "ultracapacitors" (that's the name > Epcos give them) in series connection. Six cells of 10[F] 2,3[V] gave > us an equivalent capacitance of 1.66[F] at 13,8 [V]. This bank was > charged from the 24[V] input by a DC/DC switchmode power supply while a > secondary DC/DC converter generated the main 5[V] supply from the > 13.8[V] rail of the capacitor bank. > > This way, the 5 [V] can sustain 1 [A] load current over 15 seconds > after a power failure, enough for a safe shutdown. Several hundreds of > these systems are still working after several years of operation. > > At design time, the cells employed (10[F]/2,3[V]) were the the smallest > available, both in size and capacity, but there are some real monsters. > You can take a look at Epcos ultracapacitor web page: > > http://www.epcos.com/web/generator/Web/Sections/ProductCatalog/Capacitors/Ultracapacitors/Page,templateId=render,locale=en.html > > Kind regards, > Fabian.// > Very interesting. Did you have to do anything fancy to ensure the capacitor voltages were equal? Cheers Terry
From: futrtrubl on 17 Aug 2006 20:20 The Allied catalogue has some PowerStor Aerogel Capacitors. Supercapacitor types with low ESR. ESR ranges from 0.025 to ~0.4 Ohms. Capacities up to 50F (-20% to +80% tollerance) at 2.5V (3V surge). Very small too, the 50F is 18mm diam x 40mm high. Edward tschoepflin(a)gmail.com wrote: > Does anyone have experience with supercapacitors? What's the best way > to learn more about them and what they're useful for? Any good web > links with design examples? > > We have a 1 kW transmitter for ultrasound that uses 12 electrolytic > capacitors (2200uF each) in a bank, for 26.4 mF total capacitance. The > ESR is very low so our system responds very well when transmitting > pings (lengths ranging 0.1-1.0 ms). The caps are buffering a 48V power > rail. I've thought about trying to scale the power rail down to 12 V > and beefing up the transformer by a factor of 4. > > Has anyone used a supercapacitor in a transmitter? > Thanks for the help. > -Todd
From: Fabian on 17 Aug 2006 23:23 Terry Given wrote: > Very interesting. > > Did you have to do anything fancy to ensure the capacitor voltages were > equal? > > Cheers > Terry Nothing fancy there :-) Epcos offers a specially designed voltage equalisation modules for large capacitor banks, but since ours was relatively small (it used only six caps of the smallest value), I decided to go with a simple pasive equalization network made of resistors. If you are interested, there is a detailed Epcos application note in which compares both methods with calculation examples. Best regards, Fabian Picca.//
From: Terry Given on 18 Aug 2006 01:06
Fabian wrote: > Terry Given wrote: > > >>Very interesting. >> >>Did you have to do anything fancy to ensure the capacitor voltages were >>equal? >> >>Cheers >>Terry > > > Nothing fancy there :-) Epcos offers a specially designed voltage > equalisation modules for large capacitor banks, but since ours was > relatively small (it used only six caps of the smallest value), I > decided to go with a simple pasive equalization network made of > resistors. > If you are interested, there is a detailed Epcos application note > in which compares both methods with calculation examples. > > Best regards, > Fabian Picca.// I'm just curious really. some guys I know are considering building an HVDC bus using supercaps, and my guess is that voltage sharing is pretty important, as there are so many in series (hundreds). do you have a link to the app note? Cheers Terry |