On Monday, February 4, 2019 at 8:43:17 PM UTC-5, arlen holder wrote:
a bit steaming pile of bull****



You don't have a clue how to answer that question.

You've left out the variables that *must* be included to calculate the recharge time.

Car batteries have an internal resistance that changes from the minute it's installed until it's finally dead. As it ages, the car battery's internal resistance rises and it won't draw the same current as it did when it was new. Batteries slowly sulfate over time and the more sulfated the car battery is, the larger the battery's capacitor effect is and the longer it takes to charge. Car alternators often don't provide their rated current, particularly when they are older. You left out the temperature of the components and the quality of wiring involved. Is that old Buick even idling at it's programmed rpm?

You also left out the self discharging of the battery and the standby parasitic drag from the car's computer and accessories, so that must be added to the charge time. OP asked about replenishment charge time but he also said he wants to start the car to keep the battery from self discharging. His question was two-fold, and in the real world, the best advice is keep a float charger on it or, better yet, run the car on the road to charge the battery, boil off condensation and contaminants in the fluids, and keep moving parts moving.

If OP starts that car, runs it 72 seconds and shuts it off, that battery won't last.