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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-sikkenJasper 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]

Vinatech
VEL13353R8257G
Cda
LIC1620Q3R8257
Eaton 
HS1625-3R8227
Cda LIC1840Q3R8757
specified capacitance (F)250250220750
dimensions (diameter x length mm)12.5x3516x2016x2518x40
operating temperature (Celsius)-25 +70-40 +85-15 +70-40 +85
life cycles20k (10%)30k (30%)500k (30%)30k (30%)
Current continous A0.750.751.13
Current peak A 1s51015.330
ESR AC 1kHz mOhm505010025
specified leakage current 72h/uA1051223
price at qty1000$1.90 at Vinatech$1.90 at a Aliexpress seller$8.60 at mousernot requested
measured capacitance CC 0.5A301F (+20%)220F (-14%) 228F  (+3%)761F (+1%)
measured leakage 72h/uA3124

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