Is my supercapacitor really so leaky? I have tested it.

A project log for Solar harvesting into supercapacitors

This is a 0.8x0.6 inch board with AEM10941 solar harvesting IC charging supercapacitors

jasper-sikkenJasper Sikken 02/10/2019 at 15:280 Comments

The low leakage AVX 10F 2.7V supercapacitor that I used was specified to have 30uA max leakage current, and that worried me because low power applications can have 20uA average current. Is my supercapacitor really so leaky? 

I have tested 3 different supercapacitors. One is from the well known brand AVX and two others are brandless supercapacitors from Aliexpress. 

After keeping the capacitors at a charged high voltage for 24 hours I simply measured voltage decay every day with a cheap multimeter and calculated i_leak=c[F]*(u_yesterday[V]-u_today[V])/t[s]

The tested supercapacitors

  1. AVX SCCT20B106PRB 10F 2.7V, specified to have 30uA at 72hrs
  2. Pixiuonline J469Y 1F 2.7V from Aliexpress
  3. ZHIPU CXHP series 1F 2.7V from Aliexpress, specified to have 8uA at 72hrs

And the result is put in this chart

Supercapacitor leakage current over days

Supercapacitor leakage current over days

I conclude that my tested supercapacitors have a leakage current (1uA/72hrs) much lower than many low power applications