# What capacitor size or what electrical setup can store 115 to supply a motor for 1 minute or 40secs

Hello guys, it's my first time here and I really need help. I am working on a system that produces 115VDC. Can someone help me with the size of capacitor or electrical setup I need to store the said 115VDC to supply a 110 AC/DC electric motor for 1 minute or minimum of 40secs? Also, I'll appreciate if someone can direct me to a store that might have it for sale.

active| newest | oldestTo form a very rough estimate, estimate the energy the motor will use in one minute - current x voltage x 60 Joules.

Energy stored in a cap is 1/2 x C x V^2

As soon as you draw from the cap, the voltage falls linearly, so supercaps are nearly always used with power electronics to control the voltage, by stepping up the cap voltage.

The rating of my motor is 1.45A at 110V.

According to the equation you have provided above, to run the motor for 1 minute would be: 1.45A X 110V X 60J = 9570.

Therefore, if Energy stored in a cap is 1/2 x C x V^2

(Using C = 30F i.e 30000000

1/2 X 30000000 X 110^2

15000000 X 12100 = 181500000000

Does seem to me this is too much. What do you think?

9570 is correct for the energy storage = 1/2 C V^2

9570x2 /110^2 gives C = 1.58 F. Your problem is that you can't get 110V capacitors, so you need to put 3V ones in series - 37 of them, with a value of 60F EACH.

Its going to cost a fortune.

Also, the said setup is very delicate and need to use this voltage for only about 15 - 30secs and not more than 1 min to work properly. I know I could apply the timer module to turn it off. But how do I get it to supply my module for 30secs...That is the big problem I'm have now.

Regarding size, my setup is already big enough (24" x 24" x 18"). So adding batteries to it will make it too big.

http://www.mouser.com/Passive-Components/Capacitors/Supercapacitors-Ultracapacitors/_/N-5x76s?P=1z0x813&Keyword=super+cap&FS=True

You would be much better off using 12V batteries. 10 of your typical car batteries will be able to supply 120VDC to that motor for well over 1 minute.

Please refer to my response to Steveastrouk above and let me know what you think.

Thank you