Ok ... you are not thinking about this clearly ... what you have withheld has NOTHING to do with your ability to use the EV credit. To use the credit you must have a tax liability that can be negated by the credit. If your tax liability is reduced to zero then you will get all of the withholding back as a refund. Reducing the amount you have withheld during the year will simply reduce the amount you can get refunded on the return.
