# Finding practical solutions for discharging and charging a capacitor

I am wondering can I charge and discharge a supercapacitor at the same time like a battery.

I have 1.3V going into a 10F 2.7V capacitor in series with a 0.5 ohm resistor. I calculated it will take about 30 seconds to charge to "full". And I will have a 2.6A peak current.

The minimum voltage I need is 0.9 when I discharge the capacitor. I have a 500mA current load (1700mW) that I need for startup for 1 second.

I calculated that it takes 8 seconds to discharge to 0.9V (which is more than enough time). I then need a constant 0.085mAs after the 1 second power surge.

1. Can I charge and discharge at the same time?
2. Will I be able to charge the capacitor fast enough to keep the voltage above 0.7V after the power surge?
3. Will I be able to keep my load running after the power surge when my load only requires 0.085mAs?
4. I see that every 1 second my voltage from the capacitor drops 0.05V, so when I get to 1 second I have 2500mW of power left. If my load needs 1700mW, do I subtract that and I'm left with 800mW of power to deliver to my system while I charge my cap?

I am trying to figure out if a capcitor can supply a consistent wattage even when not completely full.

• By "mAs" do you really mean milli-ampere-seconds or is that a typo? It's just "mA" for milli-amperes. Commented Jul 7, 2020 at 1:56
• @Transistor I mean milli-amp per second Commented Jul 7, 2020 at 17:06
• Amperes and mA are defined as charge per unit time so they come with seconds built-in. The units mA/s (milliamperes per second) suggests a rate of change of current. E.g., "The current is decreasing from its initial value of 100 mA at 2 mA/s." But that's not what you mean. Your sentence should read "... when my load only requires 0.085 mA?" Commented Jul 7, 2020 at 17:15
• Okay that makes sense. I read somewhere else someone was using mAs. But my load needs 0.085mA because seconds are built-in. Thank you! @Transistor Commented Jul 7, 2020 at 17:27
• A schematic is better than words. You can add one in using the CircuitLab button on the editor toolbar. Double-click a component to edit its properties. 'R' = rotate, 'H' = horizontal flip. 'V' = vertical flip. Note that when you use the CircuitLab button on the editor toolbar and "Save and Insert" on the editor an editable schematic is saved in your post. That makes it easy for us to copy and edit in our answers. You don't need a CircuitLab account, no screengrabs, no image uploads, no background grid. Commented Jul 7, 2020 at 17:30