If a battery and supercapacitor are connected in series to power a dc motor, how will the voltage vs. time graph look like? Will the voltage start higher initially than eventually decrease to the battery's voltage?
A capacitor in series will block DC so not much will happen.
If you connect them in parallel it would make more sense. Of course the voltage the motor sees is the voltage of the batteries, which no doubt have a much greater "capacitance" than your supercap.
I can't help but wonder what the use of the supercap is in such an arrangement, as they're not too useful for decoupling purposes.
Try it. You won't break anything. Report to us about what happened.
I support testing and even burning out things once in a while... you can learn a lot by doing things... sometimes its discovering "I really don't understand it" which could lead to learning more about something. I believe we learn more from our mistakes than just getting the right answer.
- the supercapacitor starts with a charge.
- the battery is fully charged.
- the battery has more energy than the supercapacitor.
Starting out it will work fine. However if you let it run until the supercapacitor is fully discharge, the battery will start to charge the supercapacitor in reverse (not good)
You could / should put a low forward voltage schottky diode in parallel with the capacitor.
However if you let it run until the supercapacitor is fully discharge, the battery will start to charge the supercapacitor in reverse (not good)
As a general rule it is not a good idea to put dissimilar power sources in series. I do agree with wolframore that it's good to try things and learn from what happens, even if that does result in a bit of smoke escaping sometimes.