I think for the car's version, the controller will be powered by the auxiliary 12v battery, or by some other 12v source, rather than by the full pack voltage. However, the pack voltage ground will still not share a ground with the 12v battery, unlike in Kelly Controllers (aahh!).
The cost of components is about the same, but there are several advantages:
First, have you noticed that controllers say things like 48v-72v, 84v-120v, etc... That's because inside the controller is a DC-DC converter to step down the voltage, and it has a limited input range. So instead, my controller will have an available pack voltage input of 12v to 156v or something like that. As long as it stays clear of 200v, it will be fine, since I'll be using 200v mosfets.
Second, you can have the controller take care of pre-charging it's own resistors, rather than having that be something external.
Third, the high voltage input dc-dc converter has quite a few extra external components needed to make sure it will function properly. The 12v-12v option doesn't have any, so it's much simpler.
This represents 6 hours of Saturday research. My eyes hurt. good bye!
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