Jump-Starting a Modern Car: What's Changed

The fundamental idea behind jump-starting a car hasn't changed: you're using a working battery to supply enough current to get a dead one going. Simple enough. But what has changed in the last decade or so is that cars have gotten a lot more complicated, and the consequences of doing a jump-start wrong on a modern vehicle can range from a blown fuse to a damaged battery management system to, in some cases, an electrical fire. So it's worth knowing what you're dealing with before you start connecting cables. If you got here because a dashboard warning light is involved, check that first — a battery light and an oil pressure light look similar in a panic and they are not the same situation at all.

Standard vehicles: the basics still work, with a few caveats

On most conventional gasoline cars, the classic procedure still holds:

1. Park both cars close enough to connect cables but not touching — both in Park, parking brakes on
2. Connect the red (positive) cable to the dead battery's positive terminal
3. Connect the other red end to the good battery's positive terminal
4. Connect the black (negative) cable to the good battery's negative terminal
5. Connect the other black end to an unpainted metal surface on the dead car — not the negative battery terminal itself
6. Start the working car, let it run a few minutes, then try the dead car
7. Once running, remove cables in reverse order

That last step about using a metal ground instead of the negative terminal — it's not superstition. Connecting right at the battery creates a small spark near a terminal that can sometimes vent hydrogen gas. Minor risk, easy to avoid.

AGM and EFB batteries (most cars built after 2012)

A lot of modern vehicles — especially ones with stop-start fuel-saving systems — use Absorbent Glass Mat (AGM) or Enhanced Flooded Battery (EFB) technology instead of a traditional lead-acid battery. These are more sensitive to how they're charged.

The jump-start procedure is the same, but you should avoid using a standard fixed-output charger on an AGM battery — use one with a dedicated AGM or smart-charging mode. A fixed-output charger can overcharge an AGM cell in as little as an hour and cause permanent damage. If you're using a portable jump starter, check that it's rated for AGM batteries. Most quality units made in the last few years are, but worth confirming before you connect it.

Finding the terminals: they're not always where you'd expect

On a lot of modern cars, the 12V battery isn't under the hood at all. Common locations include under the rear cargo floor (BMW, various Mercedes models), under the back seat (some Chevy and Chrysler vehicles), and in the trunk (some Cadillac and Lincoln models).

When the battery is located somewhere remote, manufacturers put dedicated jump-start terminals under the hood — usually a red positive post and a labeled ground point near the engine. Those are the correct connection points. Don't trace the cable back to try to find the actual battery — use the terminals that are there for exactly this purpose.

Check your owner's manual for the battery and terminal locations on your specific vehicle before you need this information. The manual is, apparently, in the glovebox.

Hybrid vehicles: use the 12V battery only

Hybrids have two battery systems: the large high-voltage traction pack that powers the electric motor, and a regular 12V battery that handles standard electrical systems and wakes up the computer that then brings the high-voltage system online.

When a hybrid won't start, it's almost always the 12V battery — not the traction pack. Jump-starting a hybrid uses the 12V terminals only, which are clearly labeled and physically separate from the high-voltage system. Do not connect cables to the traction battery or any orange-jacketed cables. Those carry high voltage and are not jump-start points. Full stop.

Some manufacturers — certain Ford and Lexus hybrid models among them — explicitly advise against conventional jump-starting entirely and recommend calling roadside assistance. Always check your specific vehicle's manual. Toyota Prius and Honda Insight models have well-documented jump-start procedures using their dedicated 12V terminals, so those are generally fine.

Electric vehicles: different situation entirely

A fully electric vehicle cannot be jump-started in the conventional sense, and you can't use an EV to jump another car either. EVs do have a small 12V auxiliary battery for their electrical systems, but the traction pack is high voltage and should never have jumper cables attached to it. If an EV won't start, the 12V auxiliary may have failed — roadside assistance handles this with a portable charger for that system. The traction pack needs a proper charging unit.

Portable jump starters

Lithium-ion portable jump starters have gotten small enough to fit in a glovebox and powerful enough to start most passenger cars and light trucks. A decent unit — 400–800 peak amps covers most passenger car gas engines, with larger V8s and SUVs needing up to 1,200A. Diesel engines typically need 1,500–2,000A or more depending on displacement — eliminates the need for a second vehicle entirely. They double as a USB power bank for your phone. Honestly, if you're going to add one item to your car kit, this is probably it. The full list of what's worth keeping in there is in what should be in your glovebox.