FastCap Chip Ultracapacitor

Question:

What happens if the Chip Ultracapacitor is operated outside of the operating temperature range?

Answer:

Operating the Chip Ultracapacitor outside the recommended temperature range reduces the lifetime.


If the Chip Ultracapacitor is operating below -40C, the extreme cold could freeze electrolyte. The freezing of electrolyte will not cause any permanent damage to the cell. If the Chip Ultracapacitor is operating above the highest rated temperature, it will diminish the life of the product. Extreme heat could cause permanent damage.

Question:

What restricts the temperature range, especially the -20°C? 

Answer:

The electrolyte limits the temperature range. Too cold: approach freezing point and ion mobility in electrolyte become extremely limited, performance drops as ESR increases dramatically. Too hot: causes capacitor lifetime reduction due to internal pressure buildup and electrolyte breakdown.

Question:

Are there plans to extend the temperature range? 

Answer:

The electrolyte limits the temperature range. Too cold: approach freezing point and ion mobility in electrolyte become extremely limited, performance drops as ESR increases dramatically. Too hot: causes capacitor lifetime reduction due to internal pressure buildup and electrolyte breakdown.


We will not extend the temperature range at this time unless a customer is interested in a custom developed product.

Question:

Do you have any characterization for operating temperatures down to -40°C?

Answer:

The lifetime derating formula depends on the operating voltage. Derating drastically extends life. The Chip Ultracapacitors end of life is defined as >20% capacitance drop or > 100% increase in ESR.

Question:

How is the effective capacitance affected with high or low levels of cycling (e.g. turned on and discharged 1x/year vs. turned on and discharged every hour for the life)  

Answer:

High or low levels of cycling have minimal impact on effective capacitance degradation. The total amount of time spend in a charged state, average operating voltage, and the average operating temperature are the 3 main drivers of degradation. 

Question:

Is there any data that characterizes ESR at temperatures below 25°C?

Answer:

This is provided in section 8 of the 01-0011-0.4 SD85-500 technical datasheet:

Odoo • Text and Image

Question:

Is there a preliminary test result showing leakage current over time (at various temperatures)?  

Answer:

Data showing leakage current overtime at various temperatures, data available in section 4 of  01-0011 SD85-500 QTR v0, QTR.

Question:

Are you able to estimate self-discharge at high temp application (138°C)?

Answer:

Leakage current should be in the range of 10-25 microamps at 138°C.

Question:

Do you have a reference design for balancing circuits for the ultracap?

Answer:

We recommend passive balancing using parallel resistors as shown below:


Question:

What is the lifetime of the Chip Ultracapacitor?

Answer:

For EOL condition of 50% decrease in capacitance and 50% increase in ESR, lifetime is 7000hrs at a max voltage (2.1V) and temperature (85°C).

Operating at a derated voltage or lower temperature will drastically extend the lifetime. 

The rule of thumb is that the life goes up by 1.7x with every 10C decrease in operating temperature or 100mv decrease in operating voltage.

Question:

What is the pad layout for reflow?

Answer:

Chip Ultracapacitor is a surface mount ceramic package.


In order to reflow the Chip Ultracapacitor, it is best to use the SAC 305 (Sn-3.0Ag-0.5Cu) solder. Reflow should be done in an inert environment such as nitrogen. The cell should be discharged completely before the reflow. A standard reflow profile in accordance with the IEC 60068-2-58 can be used. The Recommended Reflow profile is as follows.

a) Ramp: 3°C / sec ramp rate max


b) Preheat Temp: +150 to +160°C


c) Soak +150 to +160°C, 100-120s


d) Peak temp. 260°C. Tp time above 200°C should not exceed 60 seconds


e) Cooling: 6°C / sec ramp rate max


f) Maximum number of reflow cycles: 3

Question:

Lifetime at different temp and voltage? 

Answer:

The rule of thumb is that the life goes up by 1.7x with every 10C decrease in operating temperature or 100mv decrease in operating voltage.

Question:

What is the failure mode?

Answer:

The typical failure mode for the Chip Ultracapacitor is dry out of electrolyte over time causing an open circuit.

Question:

What is the leakage current?

Answer:

Typically, for supercapacitors, the cell is held at rated voltage for 96 hours, the measured current right after the end of 96 hours is the leakage current.

Question:

How to design a backup power system

Answer:

Ultracapacitors require a controlled way of charging them because of their high energy storage capacity. If an unregulated supply such as batteries is connected directly to the capacitors, there is a danger of drawing too much current when the capacitors are not charged.



For that reason, any converter with current regulation is recommended for charging ultracapacitors. A DC-DC converter is an efficient way to implement current and voltage programmed charging circuit.


Example application,