# ultracapacitors / supercapacitors

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Solar Expert Posts: 272 ✭✭
Could someone convert Farads to amps? I'm trying to figure out how much juice one of these things hold? http://www.maxwell.com/ultracapacitors/products/modules/bmod0165-48-6v.asp
The PDF on the large one (BMOD0165) says Nominal capacitance 165 F.
"They" used these as a UPS for the Palmdale sewer plant. Could they be used as a battery bank? Or, am I just smoking stuff that I ain't sharing?

• Banned Posts: 17,615 ✭✭✭
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Re: ultracapacitors / supercapacitors
audredger wrote: »
Could someone convert Farads to amps? I'm trying to figure out how much juice one of these things hold? http://www.maxwell.com/ultracapacitors/products/modules/bmod0165-48-6v.asp
The PDF on the large one (BMOD0165) says Nominal capacitance 165 F.
"They" used these as a UPS for the Palmdale sewer plant. Could they be used as a battery bank? Or, am I just smoking stuff that I ain't sharing?

Not sure there's a direct conversion. A while back there was a news release about hybrid battery/supercapacitor. There could be some future in this.

But until NAWS starts selling them, don't hold your breath waiting!
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Re: ultracapacitors / supercapacitors

Data sheet (PDF). Lets assume the "big one" at 165 Farads, 48.6 volts charged, 10.5 volts discharged. 150 Amps continuous rating:
• Watts Seconds Stored = 1/2 * C * V^2 = 1/2 * 165 F * (48.6 volts) ^2 = 195,000 Watt Seconds
• Watt*Hours = WS / 3,600 seconds per hour
• 195,000 WS / 3,600 sph = 54.2 WH full
• WS Left Behind = 1/2 * C * V^2 = 1/2 * 165 F * (10.5 volts) ^2 = 9,000 WS (not much)
• 9,000 WS = 9,000 WS / 3,600 sph = 2.5 WH "empty" of usable energy
• P=I*V= 150 amps * 48.6 volts = 7,290 Watts Peak (beginning of discharge)
• P=I*V= 150 amps * 10.5 volts = 1,575 Watts Minimum (end of discharge)
So--lets say we want to run a 1,500 watt load on this capacitor bank. Start at 48.6 volts, end at 10.5 volts (our special wide range DC inverter). Assume inverter is 80% efficient:
• (54.2 WH - 2.5 WH) * 1/1,500 Watts * 0.80 eff = 0.034 hours = 2 minutes
The equivalent 12 volt battery bank (100% to 0% dead)
• (54.2 WH - 2.5 WH) / 12 volt bank = 4.3 AH 12 volt Bank
Unless I completely messed up--Which is entirely likely...

I noticed they spec. a "cycle" as Vmax to 1/2 Vmax--so the useful energy stored will be a bit less.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 144 ✭✭
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Re: ultracapacitors / supercapacitors

To show this on a other calcutalion.

A 1-farad capacitor can store one coulomb (coo-lomb) of charge at 1 volt. A coulomb is 6.25e18 (6.25 * 10^18, or 6.25 billion billion) electrons. One amp represents a rate of electron flow of 1 coulomb of electrons per second, so a 1-farad capacitor can hold 1 amp-second of electrons at 1 volt.

So 156F * 48.6V = 7581.6 Asecond that is 2.1Ah.

This shows that the capacitor is perfect for sort time buffer. but not replacing batterys.
Even for a car charging from braking is aproblem , think how often are you braking a day , and you will see that you will waist the supercap. 1.000.000 c/d life time whitin a year.:grr

It is a nice product but to early to replace the old battery even if you forget the extra money.;)

greetings from Greece
• Solar Expert Posts: 121 ✭✭✭✭✭
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Re: ultracapacitors / supercapacitors

This capacitor is rated in charge/discharge cycle lifetime? That is strange...usually caps are rated in years only due to aging of the dielectric (unless it is air or some other durable material). A capacitor in an AC circuit might see 1,000,000 cycles in a single day!

Yet another way to look at the storage is I = C dV/dt In other words, a 1 Farad capacitor discharging at a 1 A current will drop 1 volt per second. If there was a way to pull a constant 1 A current from a 1F cap charged to 10V, in 10 seconds it would be totally drained.
• Solar Expert Posts: 144 ✭✭
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Re: ultracapacitors / supercapacitors

@Skyko,

This are not normal caps thats why the life cycle.
The local metro company in Athens greece is using this to buffer on there trains ( the new ones from korea) and is replacing whitin one year the supercaps..

Greetings from Greece8)
• Solar Expert Posts: 272 ✭✭
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Re: ultracapacitors / supercapacitors

Thank you all.... B.B. you once again amaze me, Marc the supercap + battery was designed for the Ev market where they need a surge buffer for braking & acceleration.
I guess my batteries are safe for now!? I can remember the TV repair man using a long grounding wand to discharge the "cans' in the back. They would hold a charge for years. That and the article about the Palmdale ups generating megawatts for seconds, well... stinking thinking.
Once again, I thank you all! Amps, volts & hours I understand but, farads.... I guess "they" didn't think a turbine mechanic need to know about capacitance. (13,820 rpm x 5,000 lbs of fuel / hour = 5,000 hp = ? farads) does not compute
• Solar Expert Posts: 713 ✭✭
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Re: ultracapacitors / supercapacitors

Amps are a flow of electrons, Farads are a quantity of electrons.

Basic equation is: CV = IT
Capacitance (in Farads) X Voltage (in Volts) = Current (in Amps) X Time (in Seconds)

1 farad of electrons at a charge of 1 volt will flow 1 amp for 1 second

In a dynamic situation, the math gets much worse.