We at Capacitech Energy, LLC (Capacitech) are often asked how we know the length of the cell is proportional to energy storage. We know this is true because:
The equation for capacitance is proportional to surface area. Therefore, if you have two devices with the same diameter but one is twice as long, it will have twice the surface area and twice the capacitance.
We have done a lot of testing on these devices. One of the tests are called a GCD curve where we charge and discharge the CBC devices at a constant/controlled current such as 10mA. The longer CBC devices take longer to charge and discharge. A CBC device that is twice as long as another CBC device will take twice as long to discharge too.
From experiments like the one described below!
This video features two 5cm long CBC devices connected in series and two 10cm long CBC devices connected in series. We charge them up side by side and discharge them both into an individual LED. The two 5cm CBC last about 4mins while the 10cm devices lasted about 8min.
Performance of components used:
Two 5cm CBC devices in series = 0.5F @ 3.2V Two 10cm CBC devices in series = 1F @ 3.2V