Smoked cap bank

[Gilbert Pun]

i have been using 10S2P on this rainbow boat for awhile running with great success each and every time, Castle Peak 2028 motor, Castle Peak 200A ICE ESC with homemade cap bank and 6717 CNC propeller.

Then changed to use 12S2P running for about 10 laps and it stopped in the middle of the course.

 

[Jim Caldwell]

63V caps?

Almost looks like they shorted out on bottom of the cap board, it's not lined with carbom fiber is it?

 

[photohoward1]

You increased the voltage and RPM by 20%. Did you prop down?

 

[Gilbert Pun]

63V caps?

Almost looks like they shorted out on bottom of the cap board, it's not lined with carbom fiber is it?

I am using 50V Rubycon caps, i have put 3-4mm thick resin to protect the bottom connections of the cap board, probably some water is leaking from the rubber tube connections and managed to sip on to the top of the cap board hence short circuit the first couple of capacitors.

 

[Gilbert Pun]

You increased the voltage and RPM by 20%. Did you prop down?

No, I didn't change any set up, because I have used up all 5S1P batteries that day and got some 6S1P batteries handy and the ESC said it can handle 12S !!

 

[Chilli]

The ESC may be able to take the extra voltage but the increase results in a faster spinning prop which increases amp draw significantly.

 

[John Finch]

Thing to remember is when you up the cells the rpm goes up and the motor will try to reach that RPM at the expense of the ESC, wires, Etc. You have to prop down so the motor can reach those RPM or you pull too much current trying to get there. Ask me how I know. I had to learn the hard way.

 

[RaceMechaniX]

Gilbert,

The problem is you are using 50V caps and you need something closer to 63V. The reason is with current ripple you have voltage spikes from the switching of the FETS. These spikes are both positive and negative, but when positive they add voltage to you battery voltage and the spikes can be rather high. High enough to be over the limit of the caps and this is what causes them to fail.

It is also very possible you damaged the caps in the ESC when this happened. Look for signs of bulging on the ends or if necessary you will have to split the cases and check the leads to the caps have not failed like a fuse.

Tyler