Most super capacitors (supercaps) can be discharged down to 0 V and recharged to their maximum voltage with the manufacturer recommended charge current. A simple voltage regulating LED driver with constant current, usually regulated by sensing a low side, series current sense resistor, then a voltage clamp can be used to charge a super capacitor.
Once you know the polarity and if you are curious to charge it, you can even use a RPS set it to 5.5V (or 4.95V for safety) and then connect the positive lead of RPS to positive pin and negative lead to negative pin and you should see the capacitor being charged.
When it comes to charging a super-capacitor there are two golden rules, the capacitor should be charged with correct polarity and with a voltage not exceeding 90% of its total voltage capacity. Super-capacitors in market today are normally rated for 2.5V, 2.7V or 5.5V.
Eventually, the super capacitor voltage, and therefore the charging circuit’s operating efficiency, increases so the capacitor charges at the desired constant (fast or max) charge current, ICHG, until it reaches and remains at constant voltage (CV) regulation voltage, VREG.
The most important decision for a switched-capacitor charger is selection of the CFLY capacitor. A minimum of two CFLY capacitors are required per phase, with four being optimal. Additional CFLY capacitors can be used, but returns are diminished by added cost and board space.
The switched-capacitor architecture enables the deliv-ery of high current to the battery while keeping USB cable current and voltage drops low. It’s possible to accomplish 6-A battery charging with standard 3-A-capable USB Type-C cables, or up to 10 A with 5-A-capable cables when using switched-capacitor devices in parallel. 2 W in the phone.