This is the correct way to utilize super capacitors as a rechargeable battery.
This 0.3Ah (300mAh) 5volt power bank uses 2 pcs 500 Farad 2.7volt super capacitors as storage.
It charges full from 5volt 500mA USB in 40 minutes and delivers 300mAh at 5volt.
It has a Micro-USB for charging and a 10ohm resistor limiting the charging current to 500mA and can be charged from any USB-jack.
There are 2 pcs of 500 Farad capacitors in series that charges to 5volt.
The zener diodes are used for balancing the voltage to 2.5v in each capacitor and prevent over charging of one capacitor.
A 5volt boost converter with a USB-jack utilize the power stored in the capacitors to give a steady 5volt output as the stored voltage tapers off.
Pulling 500mA from the battery makes it last (300/500*60) 35 minutes.
Pulling 100mA from the battery and it lasts (300/100*60) 180 minutes or 3 hours.
The 10ohm resistor is for limiting the charge current to 500mA so it can be charged from any computer or charger.
If you lower the resistor to 5ohm you can charge it with 1A and full in just 20 minutes. This does however require a mobile charger.
Now what can you use this for?
An emergency flash light or perhaps a mobile dremmel/hand drill.
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