A rough rule: half an hour or more
There is no exact number, because it depends on the car and on how drained the battery was. Plan on at least 30 minutes of steady driving after a jump, and understand that even that may not fill a battery that went completely dead.
A short errand is the usual mistake. Ten minutes to the gas station or the grocery store feels like a drive, but most of it is slow, and the start itself just took a big bite out of the battery. A trip like that can put back less than the start took out.
Why idling doesn't work
At idle the engine turns the alternator slowly, so it puts out about the least current it ever does. The car is also using that current to run the engine computers, the pumps, the cooling fans and the air conditioning blower. What is left over for the battery is small.
At road speed the alternator spins much faster and has current to spare. That is why driving does more for the battery than sitting in the driveway with the engine running.
Where to drive
Steady speed beats stop-and-go. A loop on the freeway or a tollway is better than ten minutes of traffic lights. If you can't drive far, do it in two longer trips instead of several short ones.
If you know why the battery died, like a dome light left on, the drive may be all it needs. If you don't know why, watch the headlights as you stop at a light. Lights that dim at idle and brighten as you pull away point to a charging problem, not just a drained battery.
Go easy on the battery while you do
Anything extra the car runs comes out of the same current. While it recharges:
- Switch off what you can do without, like seat heaters, the rear defroster and a loud stereo. In a DFW summer you will want the air conditioning, and that is fine. The point is not to add more.
- Unplug phone chargers and other accessories you don't need.
- Try not to shut the engine off at your first stop. Starting is the hardest thing you ask of the battery, and it only just got its boost.
A drained battery is not a charged battery
An alternator is built to keep a battery topped off, not to bring a dead one back to full. After a long drive the battery will be partly charged. A battery charger is the right tool for a full recharge.
Think about the next start, too. Park somewhere you could get help if it doesn't catch, and don't set out on a long trip the next morning with a battery that only just came back.
If the car starts fine the next morning, good. If it doesn't, the battery isn't holding a charge. A jump start is $49–$75, plus the $19 dispatch fee, charged once, and the driver can advise on site whether the battery looks worn out. Replacement is $239–$255 on eligible vehicles and batteries, battery and installation together.
Common questions
You can, but expect that it may not start again. Restarting takes more from the battery than anything else, and it has barely recovered.
A little, since the alternator spins faster, but it isn't a substitute for a drive. Steady driving does the job better.
If the battery is healthy and the drive was long enough, yes. If it isn't starting after a good drive, the battery probably can't hold a charge anymore.