If only he does some simple calculations.
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12V 35A 420Whr
8"x7"x5"
24 pounds
To go 100 miles, 33 kWhr, he needs 78 of them, or 1950 pounds. And deep cycle lead acid is only good for around 200 cycles, or replace them in a year or 2. Assuming that he can fit them all in his back seat.