How long do I need to let it run? Should I get gas in a can and put it in the car so while the battery is recharging it does not run out of gas?
Here are two ways to do it:
Methdo #1
Jump the car and then let it sit and charge at idle. That's what most people do. But think about what's going on. An alternator works because it's a generator working off an electro-magnet. So, with a dead battery, you don't have much of an electro-magnet. Then consider the charging capacity of a typical alternator. At highway speeds and alternator can easily put out 100 amps. But at idle, you'll be lucky to see more than 20-30 amps. So, if you're like most people, you'll crank up the heater and sit in the car for a while to "recharge" the battery. The voltage regulator inside the alternator will monitor battery voltage and tell the alternator to go to full output (battery's dead, remember?). So the alternator will go to full output at idle and that'll overheat the windings. You'll drive off and think you just saved the cost of a battery charger, tow, or a new battery. Smart. Very smart. Until a month or two down the road when you discover that your alternator is toast. Why is it toast? Because you were too cheap to buy a battery charger and used the alternator to charge your battery. The insulation melted off the windings and now it's garbage. Nice going. Battery charger $45. New alternator $400 (installed). Ah, maybe it wasn't such a great idea after all.
And for all you skeptics out there. Don't write to me and tell me this never happened to you. If it hasn't, consider yourself plain lucky. I've seen it happen so many times that I'm just surprised when it doesn't turn out this way.
Method #2
Get it jumped and back home in daylight (so you don't have to turn on the headlights) and don't run the heater. Slap a battery charger on it and set it to LOW. Let it sit and charge the battery for 12 hours. Drive the car.
The job of the alternator is to replace the juice you used while driving. It is NOT designed to bring a battery back from the dead while running at idle speed.
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Buy first at least 1 liter of gasoline in the Gas Station, fill it up on your car fuel tank. Ask your friend to drop by on your place with his/her car, you need a 1 pair of long electric cable, maybe around 2 meters, black and red that have clip on both ends, connect the other end to your friend's car and the other end to your car, your friend's car is on neutral gear and running, try to start your car and if it not work. Remove and send your batter to charging station or buy new one if is already old.
Letting the car run is probably the worst approach you could possibly use. Buy a charger or remove the battery and take it to an automotive parts store or garage to have it charged.
Get 'gas in a can'.
Idling, it can take 20 Min. or so just to make up the drain for a 'start'
Once you've got some gas in it, 'jump it and drive it around for 30 Min. or so
in second if 'in town', at moderate RPM to recharge that battery.
(You might need more than a gallon depending on the car.)
If you can jump start your car, you can then drive it to the gas station to get gas. If you're afraid of it not starting again while you're there, don't turn it off.
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