Hi guys,
I am trying to put three 10F supercaps in series with active balancer (designed by opamp, mosfet, etc) and a solar panel (10v, 100mA max) and a 6v 3.2Ah SLA Battery and a small system in parallel.
The solar panel can not supply any current to battery and system and all the currents are going to ground through MOSFETs in balanced state.
I haven't tested the3 zener diodes in parallel with supercaps for balancing instead of active circuit but they should behave similarly.
I think in this case we should use a controlling system like switch to removing the battery or supercap from the circuit in a certain time based on the voltage measurement using micro-controller.
Do you have any other idea?
When I use 3 LEDs (which have around 2v forward voltage) in parallel with supercaps for balancing, the current can go to battery for charging it and also to the system. In this case after sunset when there is no harvesting, the supercaps don't supply any current to the system or battery although there is self discharge.
Now with LEDs balancing circuit, if I remove the battery and we have only 3 supercaps in series with 6 voltage voltage across them and a circuit that draws only 1mA, in 30 minutes, the voltage across supercaps drops as 1v. Why does it discharge so fast? according to my calculation, the charge stored in the supecaps is 3.3F x 6v = 19.8 C and the charge drawn in 30 mins is 0.001A x (30x60) = 1.8 C but the voltage drop (1v) is not proportional with that even if we consider the self-discharge!
Do you have any idea?
Now I am thinking about using only one bigger supercap (100F) and two DC/DC buck converter for converting 10v of solar panel to 2.5v of supercap and the DC/DC boost converter for converting 2.5v to 3.3 of the system without using any battery and balancing circuit.
What is your idea about it?
I'll appreciate for your comments about my problems. Thanks!
I am trying to put three 10F supercaps in series with active balancer (designed by opamp, mosfet, etc) and a solar panel (10v, 100mA max) and a 6v 3.2Ah SLA Battery and a small system in parallel.
The solar panel can not supply any current to battery and system and all the currents are going to ground through MOSFETs in balanced state.
I haven't tested the3 zener diodes in parallel with supercaps for balancing instead of active circuit but they should behave similarly.
I think in this case we should use a controlling system like switch to removing the battery or supercap from the circuit in a certain time based on the voltage measurement using micro-controller.
Do you have any other idea?
When I use 3 LEDs (which have around 2v forward voltage) in parallel with supercaps for balancing, the current can go to battery for charging it and also to the system. In this case after sunset when there is no harvesting, the supercaps don't supply any current to the system or battery although there is self discharge.
Now with LEDs balancing circuit, if I remove the battery and we have only 3 supercaps in series with 6 voltage voltage across them and a circuit that draws only 1mA, in 30 minutes, the voltage across supercaps drops as 1v. Why does it discharge so fast? according to my calculation, the charge stored in the supecaps is 3.3F x 6v = 19.8 C and the charge drawn in 30 mins is 0.001A x (30x60) = 1.8 C but the voltage drop (1v) is not proportional with that even if we consider the self-discharge!
Do you have any idea?
Now I am thinking about using only one bigger supercap (100F) and two DC/DC buck converter for converting 10v of solar panel to 2.5v of supercap and the DC/DC boost converter for converting 2.5v to 3.3 of the system without using any battery and balancing circuit.
What is your idea about it?
I'll appreciate for your comments about my problems. Thanks!
