We have an AC powered, transistorized truck that has an intermittent electrical shoot through. The truck will go into high speed in the forward direction and the only way to stop it is to disconnect the battery. Putting the truck in neutral or reverse won't stop it and braking it will only slow it down. It seems that something is shorting out the system causing full battery voltage to go directly to the drive motors. This is extremely intermittent problem. The truck went 9 months without it happening and then occured twice in 4 hours.
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From what you have stated that it shoots off, i would say whatever the fault, there must be a problem in the controller, as the fail safe circuit is not working. If a fault is detected in most modern controllers, it should either drop out the contactors or prevent the system from working. So it sounds like you have 2 faults one being the fault which is triggering the truck to shoot off and the other being the fail safe circuit not working. That can do some serious damage to someone get it looked at asap.
might be a bad controller
if you apply reverse input the the encoders are reading forward motion, to continue without shutting down defies programmed logic
but i wouldnt condemn it without looking at it on a laptop (since, most likely, its a few thousand dollars to replace )
and it seems to me, it would be considerably difficult for an A/C truck to wind up with "shoot through" causing full battery voltage like a DC truck (ala PMT) since the motors work considerably differently. I would greatly doubt the controller failure, and more expect this to be a problem between the operator presence pedal and the steering hand crank.
I would also doubt that "applying the brakes does not stop it only slows it down" unless you have found at least part of the problem; a (stuck/broken/shorted) brake switch.
did you see the fault occur in front of you?
and do you have the laptop software?
It is a Still R20 and has bes been taken out of service.
no matter what the truck is. get it parked up before somebody gets hurt. please
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