# Testing few big Lithium Ion Capacitors

A project log for Solar harvesting into Lithium Ion Capacitor

A tiny board with AEM10941 solar harvesting IC charging a Lithium Ion Capacitor

Jasper Sikken 11/07/2022 at 21:025 Comments

Recently I bought a 250F and a 750F 3.8V Lithium Ion Capacitor from Aliexpress, it is manufactured by Cda. Are they good?

 250F 3.8V 750F 3.8

I compared it to other LICs from well know brands like Vinatech and Eaton. I compared datasheets, measured capacitance and measured leakage. To measure the capacitance I used my own electronic load set at a constant current of 500mA and and measured the time it takes to drop from 3.8V to 2.5V. Capacitance is calculated Q(F)= )=t(s)*0.5A / (3.8-2.5)

To measure the leakage I charged them up and every day I measured the voltage decay with a bench  multimeter and calculated leakage current using following formula leakagecurrent(A)=capacity(Farad)*(yesterdaysvoltage[V]-todaysvoltage[V])/t[s]

 VinatechVEL13353R8257G CdaLIC1620Q3R8257 Eaton HS1625-3R8227 Cda LIC1840Q3R8757 specified capacitance (F) 250 250 220 750 dimensions (diameter x length mm) 12.5x35 16x20 16x25 18x40 operating temperature (Celsius) -25 +70 -40 +85 -15 +70 -40 +85 life cycles 20k (10%) 30k (30%) 500k (30%) 30k (30%) Current continous A 0.75 0.75 1.1 3 Current peak A 1s 5 10 15.3 30 ESR AC 1kHz mOhm 50 50 100 25 specified leakage current 72h/uA 10 5 12 23 price at qty1000 \$1.90 at Vinatech \$1.90 at a Aliexpress seller \$8.60 at mouser not requested measured capacitance CC 0.5A 301F (+20%) 220F (-14%) 228F  (+3%) 761F (+1%) measured leakage 72h/uA 3 1 2 4

The CDA 250F LIC has 14% lower than specified capacitance, not perfect but not bad either. The leakage of all LICs after 72hrs is very low, less than 5uA, so it becomes insignificant for most energy harvesting application.

Conclusion: the 250F and 750F 3.8V LICs from Cda are not bad at all. The specs are good, the measured capacitance is not bad and leakage is good. For the Cda 250F the price is \$1.90 in qty1000 same as the Vinatech 250F.

## Discussions

Rob Latour wrote 11/02/2023 at 03:02 point

Thank you for this.  I just got a CDA  LIC1840Q3R8757 - not sure how to charge it for use.  How did you approach it?

Are you sure? yes | no

Jasper Sikken wrote 11/02/2023 at 07:22 point

Set your bench power supply to 3.8V and limit the current to 0.75A, then connect to the LIC

Are you sure? yes | no

Rob Latour wrote 11/02/2023 at 12:56 point

thanks very much; and for how long - or how do you know to stop?

Are you sure? yes | no

Jasper Sikken wrote 11/03/2023 at 07:58 point

Charging a 750F capacitor at 750mA from 2.5V to 3.8V takes 750F*(3.8V-2.5V)/0.75A= 1300s=22 minutes. Either you wait 22 minutes of check the current on the bench power supply, if it is 0.0A charging is completed.

Are you sure? yes | no

Rob Latour wrote 11/03/2023 at 11:44 point

Perfect, thanks for your help Jasper!

Are you sure? yes | no