I want to charge a 1F(5V) supercap with a small solar cell(6V) and when a voltage of ~2V has been reached a Teensy LC should be powered with that voltage. The teensy then regularly is measuring the voltage(using a z-diode to reduce the voltage) and charging speed. When there is enough sunlight and the charging speed is high the teensy is waiting until the supercap has entirely charged (5V) and then is starting a motor via a motor driver. Both, teensy and motor driver (pololu drv8835) are working down to 1.7V. With little sunlight the teensy is only waiting until 5V-xV until it is starting the motor to not have a too big interval between the motor runs. The Teensy is running from 1.7V on stable enough (for my taste). The problem is that when I connect the Tennsy directly to the solar cell + supercap it stops charging at 1.62V. It seems that at that voltage there is a point where the Teensy is drawing relatively much current, but does not start properly, because if I manually raise the voltage to 1.7V the Teensy is starting properly and when set to hibernate mode there is no noticeable difference in charging speed with or without connected teensy so the solar cell is sourcing much more current than the teensy draws in hibernate mode. My problem is to get past that 1.62V. I tried it with different z-diodes, a z-diode plus a standard diode, standard diodes in series, but it always starts with low current and so a voltage below 1.6V! What to do?
Btw. when the cap has charged to about 1.7V and the teensy is up and running it bypasses the z-diode(currently used, but not working as expected) with one channel of the two channel motor driver to be able to run down to 1.7V.
Thanks for the answers in advance.
Btw. when the cap has charged to about 1.7V and the teensy is up and running it bypasses the z-diode(currently used, but not working as expected) with one channel of the two channel motor driver to be able to run down to 1.7V.
Thanks for the answers in advance.