What Gauge of Jumper Cables is Suitable for Car Battery?
4 Answers
For battery jump-starting cables, 25 square millimeter copper wires with a length of about 2 meters are recommended. Since starting the engine requires a large current, and the battery voltage is low with even greater current, the resistance of the jumper cables should be as low as possible. Below is the correct connection sequence and an introduction to preventing the rescue vehicle's battery from draining: Connection Sequence: When connecting the cables, it's best to follow the correct order: connect the positive terminal first, then the negative terminal. Additionally, the clamps of the positive and negative cables must never touch each other, and the positive cable clamp should also avoid contact with any metal parts of the vehicle. Preventing the Rescue Vehicle's Battery from Draining: After connecting the cables, you can start the rescue vehicle and gently press the accelerator to increase the engine speed and charge the battery, preventing the rescue vehicle's battery from draining as well. If the rescued vehicle still fails to start after connecting the jumper cables, it may be due to severe battery depletion. In this case, wait for about 10 minutes before attempting to start the vehicle again.
Last time I helped a friend jump-start their car, I used a 16 square millimeter cable, and it worked smoothly—the small car started right up. However, I remember lending it to someone with a large SUV, which required more current, and the 16 square millimeter cable struggled—the engine wouldn't turn over. We later switched to a 25 square millimeter cable, and it worked fine. Generally, for regular sedans, a 16 square millimeter cable is sufficient for daily jump-start needs, handling around 150 amps. But for larger vehicles or cold engine starts, it's better to have a thicker 20 or 25 square millimeter cable to ensure quick current flow without overheating. The key when jump-starting is to securely attach the clamps to the positive and negative terminals—don’t mix them up, or you risk a short circuit and damaging the equipment. It’s not as complicated as it seems—just pick a good-quality branded cable. That’s how I’ve always done it.
I personally place great emphasis on safety and always worry that cables that are too thin might overheat, melt, or even catch fire when using jumper cables. It is generally recommended to choose cables with a cross-section of 20 square millimeters or more, such as 20-25 square millimeters, as they are less likely to cause issues even under high current. The instantaneous current during a car startup can exceed 200 amps. If the cables are too thin, the voltage may be insufficient to crank the engine, and it also increases risks. I once tried using cheap 16-square-millimeter cables, and they became too hot to touch as soon as they were clamped on, so I quickly replaced them. It’s best to buy models with heat-resistant sleeves and check whether the clamps make tight contact. Safety comes first—don’t skimp on small expenses. It’s wise to carry a thicker cable for long trips. In short, insufficient cable size is the root of potential hazards, and making a reasonable choice can save a lot of trouble.
From a cost-saving perspective, 16 square millimeter jumper cables are usually sufficient—they're affordable and lightweight, making them my go-to choice when on a tight budget, as long as they're not used for high-displacement vehicles. Lower current isn't an issue, but the cables have a shorter lifespan and are prone to aging and damage over time. In contrast, 25 square millimeter cables are more durable and handle higher currents better, though they come at a higher price. Weighing the options, 16 square millimeter cables often suffice for most situations. The key is to avoid cheap, no-name brands and ensure sturdy connectors to prevent loosening. For car emergency kits, I recommend keeping both sizes and switching based on the vehicle's needs—it's economical and practical. Don't compromise safety for short-term savings; smart pairing is crucial.
