"Backdriving" Motors -- Safe for Victors?

[Ken Streeter]

Last year due to wiring errors our team destroyed far too many Victors for our team's budget to handle. Our troubles at the time were due to connecting Victors "backwards" with the +12 Power/Ground "input" connections instead being placed on the M+/M- "output" connections. We found that doing this and then turning on the power to the robot immediately results in a big popping noise and bright flash -- later followed with the need to call IFI with a credit card number... (Call this a lesson from the school of hard knocks!)

However, enough of history... back to the present time, when we are being extremely cautious in order to keep our Victors working properly...

Our question is whether or not it is likely that the Victors can be "burnt out" by being backdriven. A search through ChiefDelphi turned up two previous threads that discuss this issue, but I don't feel that the question was resolved of whether or not backdriving the motors is generally safe for the Victors:

• 2004 Thread on "Victor burnouts"
• 2006 Thread on "Back EMF Safe for Victors?"

The two scenarios of which we are concerned are as follows: (The first is the primary concern, as we are not aware of a good way to avoid it.)

• Scenario 1: We plan to have Fisher Price motors connected through a gearbox (either the KOP FP Gearbox or a BaneBots planetary gearbox) to drive a robot lifting mechanism. In order to "reset" the mechanism to get it to fit back in the robot volume after completing a match, the mechanism would be backdriven (presumably with the robot power off). This would backdrive the motor for just a few seconds, surely for no more than a couple thousand rotations.
  
• Scenario 2: We plan to have small CIM motors connected through the BaneBots planetary gearboxes supplied in the kit as the primary drive for the robot. Pushing the robot with the wheels on the ground will backdrive the motors through the gearbox. We have always sought to avoid this situation in the past by simply carrying the robot, but we figured we'd ask if pushing the robot in this way is likely to be a problem, since many other teams could benefit from a definitive answer on this scenario.

Any conclusions or additional experience from the electrical gurus out there?

Thanks!

--ken