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)	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.