The cutting ratio of heating wire depends on the output power required under voltage. The length and thickness of heating wires with different material resistivity are different. Suppose 1200W, 220V, and the required resistance is r = 2202/1200 = 40.3Ω. If the nickel-chromium wire with a wire diameter of 0.5mm is selected, the resistance per meter is about 5.7 Ω. The length of the resistance wire should be 40.3/5.7 ≈ 7.1m. The wire is connected to the battery, and the actual power P=48*48/ 100=23W, which is similar to that of an electric soldering iron. As for the temperature, it depends on the specific use. If you want to get 500W power, the resistance is R2 = 48 * 48/500 = 4.6ω Ω, and the resistance of the original heating wire is R = 220/2.5 = 88ω Ω, so you need to cut off the original length118.