Handbook for Sound Engineers

Power Supplies 691

where,

Run time is in minutes,

dc load is in watts.

19.9.1 Ultra Capacitor Characteristics

Ultra Capacitors do not degrade in time as batteries

do so reliability is high.

UCs have a capacity one million times that of a stan-

dard electrolytic capacitors. This is accomplished by

depositing carbon on an aluminum substrate which can

be etched it give dramatically increased surface area and

low impedance. A typical UC 30 mm × 50 mm can

have up to 400 F of capacitance with a working voltage

of 2.5 V.

The energy stored in a capacitor is CV^2 /2. To have

the same energy density as current Lithium Ion

batteries, the working voltage for a given size would

have to be increased to 5 V. This would yield 4 times

the energy density of current UC technology and make

UCs the ultimate energy storage device. It is just a

matter of time before technology reveals materials

capable of having dielectrics in the 5 V or higher range

and making batteries as we know them today obsolete.

Charging. Ultra Capacitors have extremely low internal

impedance so power limited charging must be used to

avoid overloading the charger. UCs are also sensitive to

voltage. They must be operated below their rating to

avoid destruction. Designers tend to charge them as

close as possible to ther maximum voltage to extract the

maximum energy from them.

Figure 19-26. Ultra capacitor UPS power supply module.

Courtesy Ram Technologies LLC.

Figure 19-27. Typical installation of a ultra capacitor UPS module in a computer. Courtesy Ram Technologies LLC.