"I want to power a module that requires 3.3V and 500mA minimum for startup. I have a solar panel that outputs max 3V at 70mA and a 3.3V 3A max output boost converter. I know I need a super capacitor or a capacitor bank to store energy so I can get the current needed for start up. Also, my module only needs around 500mA for less than 1 second. I will probably consume an average of 10-40mAh.
I do not know too much about power electronics, but I want to know how can I design a capacitor power bank circuit that can handle 3.3V, can store a minnimum of 500mA, only takes less than 5 minutes (if possible) to charge the capacitor bank to 500mA, discharge the current for 30ms or more and have the capacitor discharge when full.
This 500mA current is only required once per day or when the solar panel drops below 1V.
I only want my device to be on during the day."
Above was my previous question. Below is my new information!
- My size requirement is a 2×2 solar panel
- Cannot have a battery, customer wants power only during day or peak
hours - The figure is what I have been calculating on the wattage required
Will this work?
- I have purchased the evaluation board for the boost converter and set
a breadboard circuit up with smaller capacitors and supplied voltage
to a red led, but it doesn't have consistent power, it blinks fast
like a relay.
Also, when i supply this power to my wifi module, will this provide consistent power throughout the day after the startup requirement?
Best Answer
Will this work?
You'll need more capacitors, a lot more. Another problem is you'll also need an MPPT tracker and capacitor charge controller. A bigger solar panel with a higher voltage would also be recommended. The best option would be to use a battery.
The boost converter only works to 0.9V so there is energy stored in the capacitor that cannot be used.
You'll still get \$ Q=1/2*C*V^2 \$
\$ 1/2*1F*3V^2-1/2*1F*0.9V^2=4J \$
4J/(1700mW seconds) = 2.35seconds
Which means to run this for 1 hour you'd need 30 1Farad capacitors in parallel, and it would take a long long time to charge up.
The second problem is the above calculations are only good if the capcitor actually reaches 3.3V. In the diagram above the solar panel could only charge the cap to 1.3V, which will yield even less energy storage.
The third problem is you need a solar charge controller, because a capacitor is a really high load, the solar cells won't be operating at their maximum efficiency. Because of this the capacitor may not charge at all, or take a very long time.
The diode also does not help and contributes to a lot of loss from the panel.