stan2004 posted:If the numbers (size/fit, cost, engine keep-alive time, etc.) work for your particular application then so be it. I recall the "tennis ball can" thread where the proposed cap to keep the engine operating during power loss was the size of a can of tennis balls!
If component technology has improved to the point where it's practical, then by all means. Though I think GRJ's idea of a rechargeable battery (vs. a capacitor) might have better cost-size-performance tradeoffs for the stated application.
Haha, I hadn't seen that before! 
The reality is not quite that bad though. Here's a 10F 2.7V cap that I have laying around:
Assuming an 85% conversion efficiency and operation between 1.5V and 2.5V, that's enough energy to run a motor at 14V and 0.5A for 2.5 seconds.
