Actually to be safe do it for a 30 minutes. Then replace the cable to the battery. Start up the car and let it idle for about 10 minutes. Don't hit the gas pedal during this time. This time allows your ECU to make new data based on how much air it sees coming into. Use this time to reset your radio stations and clock. After 10 minutes is up, turn the car off.

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Catapultam habeo. Nisi pecuniam omnem mihi dabis, ad caput tuum saxum immane mittam.