18:50 16-12-2025
How to jump-start a dead car battery: the 5-10-15 rule
Learn how to safely jump-start a car battery in cold weather with the 5-10-15 rule, plus the correct cable order and quick alternator and battery checks.
Early autumn frosts have a knack for exposing a car’s weak link—the battery. Trouble usually shows up after a long park-up or a sharp drop in temperature: you turn the key or press the start/stop button, the starter barely turns, and the dashboard lights glow faintly. In most cases, a flat battery is to blame. A jump-start from another car helps, and the key reference here is the 5-10-15 rule. Mechanic Alexey Stepantsov outlined it in an interview with 32CARS.RU—простое правило, которое часто экономит утро и нервы.
Why batteries fail more often in autumn and winter
Sometimes the reason is as simple as forgetfulness: headlights or the audio system left on with the engine off. But in cold weather the issue can appear even without driver error. Low temperatures slow the battery’s chemical reactions, so it delivers less power. Age makes it harder for a battery to hold charge, and high summer heat also speeds up degradation. Put together, that’s why cold starts get tricky.
How to jump-start from another car: prep and safety
The quickest fix is to feed current from an external source—another car with a healthy battery—using jumper cables.
Before connecting, tick off the basics: both cars should be parked securely, ignition off, parking brakes engaged. Check where the battery is located (some cars hide it in the trunk), and position the cars so the cables reach comfortably without being stretched.
The positive terminal is usually red and marked “+”, the negative is black with a “-”. If access is awkward or the battery is hard to spot, many cars have dedicated under-hood jump points, clearly labeled.
Connecting the cables: the right order
Connect the red cable to the “+” terminal on the donor car and then to the “+” terminal on the car with the dead battery. Make sure both clamps bite firmly.
Connect the black cable to the donor car’s “-” terminal. Attach the other end not to the dead battery’s negative terminal but to bare metal on the engine or body of the car with the flat battery—ideally an engine lifting eye or a bolt on the block, away from the battery. This helps reduce the risk of sparks.
The 5-10-15 rule: timing your steps
To keep things simple and avoid mistakes, use the 5-10-15 principle—it sets the pauses between stages.
5 minutes: after connecting the cables, start the donor car and let it idle for about five minutes so current can begin topping up the flat battery.
10 minutes: if the battery was completely dead (for example, the dash lights wouldn’t even come on), wait at least ten minutes to give it more charge.
15 minutes: once the car with the weak battery starts successfully, remove the cables in reverse order. Then drive for at least 15 minutes so the alternator can replenish the charge properly.
If it won’t start again after a cold night: battery or charging system?
If the problem returns after a few days, two common culprits remain: a tired battery or issues in the charging system (alternator, voltage regulator, wiring losses).
To check the alternator with a multimeter, select DC voltage, 20 V range. Place the red probe on the battery “+”, the black probe on “-”. Measure with the engine running: normal charging voltage typically falls between 13.8 and 14.6 V. Deviations can point to faults in the alternator, the regulator, or the electrical system.
It also happens that voltage looks fine but cranking is still weak. In that case, the battery needs a load test. Under load, voltage shouldn’t drop below 9.5 V—the result will show whether it’s time to replace the battery.