I am trying to design a circuit for a device that will only run for around 20s at a time. For that 20s, however, I need to power two brushed motors (with connected propellers) that together pull around 5a @ 9v under load.
For my application I need a near constant static thrust for those 20s. I think the easiest way to do this would be to hold the voltage across the motors constant. I am looking to minimize weight, however, and need a power source that is rechargeable, and only has a little bit more than the energy required for this application.
What circuit/power source should I choose?
One option might be to use a voltage regulator to keep a constant voltage for those 20s and choose the smallest possible battery that would not drop below the regulator's minimum input voltage for the duration of the 20s (with some headroom).
To eliminate the voltage regulator is there any power source that is both rechargeable and can output near constant voltage for the majority of its life cycles? I'm guessing no.