In jump-starting a car, the positive terminal and cable are red, while the negative terminal and cable are black.
Color coding saves time when a battery is flat and a helpful driver pulls up. Still, labels and symbols matter more than paint. The + mark and a red cover usually point to the positive side. The − mark, a bare post, or a black cover mark the negative side. The steps below show how to match colors and symbols, connect in the right order, and finish safely.
Positive vs. negative: quick color guide
Use both color and markings to avoid a mix-up. The table is a fast reference you can scan before you clamp anything. For a deeper walkthrough with photos, see Consumer Reports’ jump-start guide.
| Part | Typical color | Marking or clue |
|---|---|---|
| Battery positive post | Red | “+” symbol, red cap, or red cable |
| Battery negative post | Black | “−” symbol, often bare metal or black cable |
| Jumper cable positive clamp | Red | “+” on clamp body or tag |
| Jumper cable negative clamp | Black | “−” on clamp body or tag |
| Portable jump starter red lead | Red | Matched to “+” port |
| Portable jump starter black lead | Black | Matched to “−” or “GND” port |
What color is positive when jump-starting a car? practical ID tips
Look for a plus sign first. If the battery top is dirty, wipe it so the symbols are clear. Some cars hide the battery or place it in the trunk, with small under-hood posts for boosting. Those posts are marked with + or −. If a plastic cover sits over a post, it is usually red and marked +. If colors fade, follow the cable back from the starter fuse box: the thicker lead that feeds that box comes from the positive side.
How to read the terminal area
Many batteries cast the symbols into the plastic next to each post. Others print them on stickers. Use the shape as well: the positive post can be slightly wider than the negative on some designs. Do not guess from cable routing alone. Trucks and some European models flip battery positions, and that can throw your eye.
Where the battery might live
Under-hood is still common. Some models place the battery under a seat or in the trunk to balance weight. In those cases the maker provides remote jump lugs in the engine bay. Use those lugs, not the battery posts, so you always have a sturdy ground and safe clearance near belts and fans.
Safe connection order for jumper cables
Follow a fixed order every time. It keeps sparks away from the battery and helps both cars’ electronics. If you want a printable checklist, AAA’s step-by-step matches the sequence below.
The four clamp steps
- Red to dead: Clamp the red cable to the positive (+) post on the weak battery.
- Red to donor: Clamp the other red cable to the positive (+) post on the good battery.
- Black to donor: Clamp the black cable to the negative (−) post on the good battery.
- Black to metal on dead car: Clamp the last black cable to a clean, unpainted engine or chassis ground on the weak car, away from the battery.
Start, then remove in reverse
Start the donor car and let it idle for a few minutes. Try starting the weak car. Once it runs, remove the cables in the reverse order: ground on the revived car, negative on the donor, positive on the donor, then positive on the revived car. Keep clamps from touching during removal.
Ground points that work
Use a thick, unpainted bracket, a designated ground stud, or a bare bolt on the engine block. Skip thin sheet metal tabs or the battery hold-down. A solid ground reduces arcing and noise in the car’s wiring.
Portable jump starters
A booster pack is handy when no second car is nearby. Clip red to the positive post, black to a ground point on the car with the flat battery, then follow the pack’s power button and start sequence. Many packs include reverse-polarity protection, but you still need to match red to + and black to a safe ground.
Why the color rule matters
Battery gases can ignite if a spark hits near the vent. That is why the last black clamp goes to a ground point away from the top of the weak battery. The habit also helps you double-check polarity before any current flows. A single crossed clamp can fry fuses or control modules.
Common mistakes and simple fixes
Crossed clamps
If you spot a wrong connection, stop before starting either car. Remove the cables, wait a minute, then reconnect correctly. Look for any melted insulation or blown fuses if you saw a spark.
Clamps on corrosion
White or green crust blocks current. Lift the clamp, brush the post with a wire brush or a clean key, and re-clamp on bare metal. Do not touch the residue with bare skin.
Loose, bouncing cables
Route cables so they clear belts, fans, and the radiator. If a clamp walks off a post, you will get arcing and heat. Re-seat the clamp until it grips firmly.
Revving hard right away
A slight rise in idle on the donor car helps. Heavy revs do not. Give the weak battery a minute or two, then try the key. If the starter clicks only once, wait another minute and try again.
Cable and tool picks that make life easier
Thicker wire moves more current with less drop. For small cars, 6-gauge is fine. For SUVs and trucks, 4-gauge is a smart pick. Springy, copper-toothed clamps bite better, and a carry bag keeps the set clean. A small digital multimeter can confirm polarity and help track a bad connection.
Second look: order and safety at a glance
Pin this list in your glove box if you like quick checklists. It repeats the clamp order and the take-off order in one place.
| Step | What to clamp | Why it helps |
|---|---|---|
| 1 | Red to positive on weak battery | Marks the target post early |
| 2 | Red to positive on donor battery | Completes the positive path |
| 3 | Black to negative on donor battery | Builds the return path |
| 4 | Black to ground on weak car | Moves sparks away from battery |
| Remove | Reverse the order above | Cuts risk of arcing |
Special cases: hybrids, EV models, and start-stop
Hybrids and EVs use a small 12-volt battery for locks and control units. That little battery can still go flat. You can boost the 12-volt system on many models, but never touch orange high-voltage cables. Use the maker’s jump posts and follow the manual. If the car shows damage after a crash or flood, do not attach cables.
After the engine starts
Keep the revived car running while you coil the cables. Then drive for at least 20 to 30 minutes so the alternator can restore charge. If the car stalls or needs another boost soon after, get the battery tested. A weak battery often shows up in cold weather or after short trips with the lights and blower on.
Quick troubleshooting
Lights work but no crank
The battery may not be the only issue. A corroded ground strap or a worn starter can mimic a dead battery. Check that the clamps feel warm and firm after a short charge. If they stay cold and the car still clicks, the fault may sit elsewhere.
No lights and no click
Check the fuse that protects the battery feed. Many cars place a large fuse or fusible link near the positive post. A hard short can pop it. If that link is gone, a jump will not help until it is replaced.
Starts, then stalls
Loose battery posts or a failing alternator can cause this. With the engine idling, tap the headlight switch and rear defroster. If the idle dips hard or lights fade, charging output may be low.
Safety recap
Match red to + and black to a ground on the weak car. Use a fixed clamp order, keep clamps from touching, and work in a clear spot away from traffic. Eye protection and gloves are smart picks. If the battery case is cracked or swollen, skip the jump and call for roadside help.