It's probably a packaging problem. The low, flat floors offer little space to put things like batteries. Users would probably have to give up "fold-flat" seating. Minivan noses are also lower and more compact, so fitting in the electric drivetrain is probably an issue. Add in the fact that the minivan segment is shrinking.
Give Chrysler credit for choosing a minivan as one platform for it's (hopefully) forthcoming EV hybrid.
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