# How to choose an ultra capacitor?

1.Things you must know before selecting an ultra capacitor

What kind of ultracapacitor can meet your requirements? What are the critical parameters for ultra capacitor ? We will illustrate this using the ultra capacitor product system of SPS Technology as an example. The key parameters include voltage (V) , capacity (F) and rated current (A).

the-ultra-capacitor-product-system-of-SPS

In chosing an ultra capacitor for a specific application, there are several factors, such as power requirement, discharging time, and voltage variation should be considered. To make it simple, two types of parameters must be clear: 1) the range of working voltage; 2) power output value or duration of current output.

2.How to calculate the capacitance of ultracapacitor

(1)Constant current, when current and duration of current output remain the same:

C=It/( Vwork -Vmin)

For example：Vwork＝5V；Vmin＝4.2V；Working time t=10s；Current I＝100mA=0.1A, the capacitance is C.

C =0.1*10/(5 -4.2)=1.25F

So an ultracap of 5.5V1.5F is OK.

(2)Constant power, when power output remains the same:

C*ΔU2/2=PT

For example, when a capacitance continues to discharge for 10 seconds under the constant power of 200KW, the range of working voltage is 450V-750V, and the capacitance required is C:

C=2*200kw*10/(7502-4502)=11F

So an ultra capacitance of 750V11F could meet the requirement.

If after calculation, the desired capacitance is beyond the capacitance of a single cell, we could connect multiple ultracaps in series or parallel connection into a module, to satisfy customers’ specific needs.

Capacitance for multiple cells in parallel connection: C=C1+C2+C3+…+Cn

Capacitance for multiple cells in series connection: 1/C=1/C1+1/C2+…+1/Cn

Notes: This article doesn’t discuss the structure and electrode materials for ultracapacitors, because non-quantitative parameters are not meaningful factors in selecting the right ultra capacitor. It is important to note that there is no universal energy storage components, the combined use of different kinds of energy storage device has become the best choice. At the same time, ultra capacitor is becoming the mainstream energy storage device while being used together with  other kinds of energy storage devices to leverage their respective advantages.

Supreme Power Solutions Co., Ltd. (SPS) is a leading manufacturer of ultracapacitors, as well as a provider of ultracapacitor energy storage systems and technological solutions. Our products have wide industry applications, such as new energy vehicles, wind turbines pitching control systems, trams and subways, smart grid, micro grid, heavy duty machineries, intelligent instrument, etc. We support more than 200 customers, and our products are exported to 26 countries and territories.

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