Thanks for your feedback and I tried the following:
1. I ordered and received your 2X30A controller from Pololu robotics
2. Configured it the same way as 2X15A contoller (default settings, except for single channel mode); saved settings
3. Tested basic functionality in Ion Studio and it worked well.
4. Performed auto tuning (default medium level) . Got the P= 5057, I= 150.8, QPPS = 850,000
5. Since you suggested less aggressive tuning I used P = 100, I = 1.0 in the Arduino control program
6. I used the same motor and decoder as last time and powered everything from 12V 7AHr batteries in series to give me about 25.5V. I also maked sure to use 1K to slowly charge caps on the controller when connecting it intially.
7. On the Arduino controller I set up a program using the roboclaw.SpeedAccelM1 command to step from 50,000 PPs to 750,000 PPS in increments of 50,000 PPS (with 30 seconds at each step) and then back down to 50,000, and stop, 5 minute break and then again ramp up and down.
8. It took about 5-7 minutes to finish the first cycle and was monitoring roboclaw temperate and RPM in ION Studio (arduino was issuing commands via serial port and roboclaw was also connected to the computer USM port. I was keeping a close eye on in these first 7 minutes and PPS were right on target, roboclaw temperature went from around 29 to 34 deg C. Motor was audibly running very smoothly and it look really good. Then the motor came to a full stop and waited for 5 minutes
9. At this point I decided to let it run on its own few more cycles to just make sure it is all good.
10. I left my testing area for a few minutes and then came back and motor was running and I focused my attention to another task on a different computer.
11. The sometimes after I heard a popping sound (not very loud at all) I directed my attention to the controller and saw that it was starting to smoke and catch on fire. I was very lucky to be there when it happened to put the fire out. It was quite bad and the controller completely melted in 2-3 seconds.
Please let me know if you have any idea of what might have happened here. I am not sure what to do at this point. I invested quite a bit of time and money into your controllers and I really like the features but I am not sure for how to proceed ahead. I would really be glad to hear if I made any obvious mistakes in my setup that you can point to. Please let me know if you have any detailed questions before you cam make some suggestions.