So i have this motor controller i got here http://www.ebay.com/itm/221043792022?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 , it is listed as being able to handle 68A stall current on a 36v circuit. will this controller handle two motors of 30A stall current on a 12V circuit?
I don't know. Google for: Infineon BTS 7970 It seems that this driver is discontinued. And the peak current is 68A, but I don't know what the continues current might be (probably depends on the heat sink). How sure are you that the BTS 7970 is under the heat sink, and not a lesser one ?
Probably yes, the same time max current 68A for chip doesn’t mean that board itself can handle such current. Based on pictures, width of traces, I’d say it depends on a load, how fast motor gaining a speed
There is another concern to be considered... At 12 volts the resistance losses (Wires and PCB traces) are 3 times as large.... Might actually help in that the currents will be somewhat more limited by the wiring. My choice for short runs of wire at that current would be 8 Ga. for runs under 3 feet and 6 ga if longer. I do however try to be as conservative as possible, Especially as "Plain old Copper" wire has a tempco of +3300 PPM/Deg... which means that as the wire heats up it gets higher in resistance... which makes the wire get hotter which makes... . I used to work with Mobile Telephones that had transmitters in the 50 W range and 2 way radios that had transmitters in the 100 - 200W range... 50W out means about 4.5A @ 12V X 50% (or less) efficiency which can mean as much as 8A power required from the power supply and small long power supply wires meant transmitters that did unusual or unexpected things because the power supply was "Soft". Anything worth doing is Worth Doing Right.