Jump start or new battery? How to tell which you need

A jump is enough when the battery is fairly new and something obvious drained it, like lights left on or a door left open overnight. A new battery is the smart move when it's three or more summers old, has needed a jump before, cranked slowly before it died, or won't hold a charge after a drive. If you aren't sure, get it tested after the jump.

What a jump does

Jump-starting borrows current from another battery to turn your starter. Once the engine runs, your alternator takes over and starts recharging your battery. That's it. It doesn't repair anything.

If the battery is healthy and was just drained, a good long drive brings it back. If it's worn out, it will start this once and leave you stranded again, often the next morning.

When a jump is probably enough

• The battery is under two years old.
• You know what drained it: headlights, dome light, a charger, a trunk left ajar.
• It was starting normally before this.
• After the jump and a 30-minute drive, it starts fine again.

When it's time for a battery

• It's old. Around three summers or more in Tampa Bay.
• It's the second jump. A battery that's needed two jumps in a short time is telling you something.
• It was slow before it died. That means it was already weak.
• It won't restart after a drive. It isn't holding charge.
• It died for no reason. Nothing was left on. Either the battery is failing or something is draining it. Battery dies overnight.
• It's swollen, leaking or smells. Don't jump it. Replace it.

Why one deep drain hurts

Lead-acid batteries hate going completely flat. Each deep discharge hardens some of the sulfate on the plates and costs capacity permanently. In heat, the damage happens faster. A healthy young battery can usually recover from one deep drain. An older one often can't.

After a jump

If you jump it and keep it:

1. Drive at least 30 minutes, preferably not in stop-and-go traffic. Idling in the driveway doesn't do much.
2. Don't shut it off at a quick stop if you don't need to.
3. Get it tested within a day or two. A test right after a long drive can still mislead, but a test that shows a weak battery is a clear answer.

Know that an alternator isn't really a battery charger. It's built to top off, not to rebuild a flat battery. A proper charge from a charger does a better job than a drive.

Jump boxes and modern cars

Portable jump packs are handy and safe for most cars when used correctly. On start-stop cars and cars with the battery in the trunk, use the jump posts under the hood. Follow the manual. Connecting to the wrong points on a modern car can damage electronics.

Hybrids

A hybrid with a dead 12-volt won't power on. It can often be jumped from a jump pack using the jump terminal under the hood. Don't use a hybrid to jump other cars unless the manual says it's okay. Hybrid 12-volt batteries.

What we do on a no-start call

We come out, test the battery and the charging system, and give you the honest picture.

• If the battery tests good and something drained it, we jump it and you're done.
• If the battery tests bad, we show you and give you the replacement price. You decide.
• If it's something else, like the starter or alternator, we tell you.

Jump start pricing is on our prices page. See jump start and no-start help.

The costly mistake

The expensive move is jumping an old battery over and over. Each time it leaves you stranded, you lose time, maybe a tow, maybe a missed shift. If the battery is old and has started failing, replacing it on your schedule beats replacing it on its schedule.