Service life of electric vehicle battery

Service life of electric vehicle battery

"How fast can this electric car run?" "This electric car, change the battery every few years and change tens of thousands of dollars at a time?" These three questions are basically the most frequently asked questions by general users and sales of new energy vehicles. How fast and how far you run is easy to solve, and you can basically estimate it after running a few laps. Endurance is not a simple test drive. Anyone with a little experience in automobile maintenance knows that the battery belongs to the vulnerable parts of traditional gasoline vehicles, with an average life of about 3 years, and needs to be replaced when it arrives. A small car battery costs several hundred dollars. Isn't a few hundred kilograms of battery for an electric car sky-high? The money saved by years of hard charging is not enough to change the battery! Many people hold similar views, and it seems reasonable to mention the life of battery accessories.

First, the classification of power batteries. At present, the power batteries used in automobiles can be roughly divided into lead-acid batteries, lithium batteries and nickel-hydrogen batteries. Among them, Ni-MH battery is only used in Toyota's plug-in hybrid vehicle and is not suitable as a separate power supply; Lead-acid batteries are mainly used in low-speed electric vehicles, that is, as the saying goes, "having fun in the old age"; Lithium battery is the most widely used power battery for electric vehicles. Lithium batteries are divided into many types according to different materials. At present, the most mature lithium batteries are ternary lithium batteries and lithium iron phosphate batteries. Both types of lithium batteries are basically used in the market.

Second, lead acid may need a leash, Ni-MH is Toyota's carnival, and lithium battery is king! Let's start with lead-acid batteries. It's actually just a battery in an ordinary car. After many pieces are connected in series and parallel, they can be directly used as power supply. This kind of battery has a small discharge current (the result is what we usually call "car stuffy") and the model is not fast. The fastest speed is about 60 kilometers per hour, and the service life is short. It must be replaced in about 3 years. The advantages are low production threshold, low price, low requirements for protection circuits and equalization circuits, and can basically be produced by hand workshops. Disadvantages: slow speed, low power consumption and short service life. New energy vehicles that meet the national requirements do not use lead-acid batteries. However, many of the impressions left by this kind of battery in people's minds have been directly transferred to lithium batteries.

Two kinds of lithium-ion batteries also have different "tempers". Let's talk about ternary lithium batteries first. Typical cars are Tesla, Beiqi E200EV, Jianghuai IEV5, Chery eQ, etc. It is characterized by high energy density and large capacitance under the same volume and weight. Good battery consistency and mature production technology. Theoretically, the cycle life of this battery is about 1500 times. In actual use, the battery can be discharged by Wally for more than 800 times, and the battery can be controlled to discharge at 25% to 75%, and the actual use can reach 1200 times or more. Seeing this, do you want to say, 800 times, 1 time a day, 1 time, less than 3 years? Here, let's explain the concept of complete cycle. Refers to a cycle in which the battery is fully charged and then discharged.

If 75% is used up from 100% and refilled every day, and a cycle is completed in 4 days, the service life can reach 10 years. If the ordinary ternary lithium battery electric vehicle has a battery life of 200 kilometers, it can actually travel 1 80 kilometers per cycle, and it can travel 144000 kilometers per 800 cycles. Taking normal attenuation into account, 120000 km is also stress-free. At the frequency of 1 day 60km, 10 years can be used. However, if we pay attention to light charging and light discharging, and maintain the battery well, we need 1.200 cycles,1.50 thousand kilometers, which basically covers the service life of the family car, that is, the battery has the same life as the car, and there is no need to replace the battery during the whole cycle. The life of the battery is the same as that of a car, so there is no need to replace the battery during the whole cycle.

Let's start with lithium iron phosphate batteries. Representative models include BYD Qin, BYD Tang, BYD E6, Tengshi and JAC IEV4. This battery is characterized by long cycle life, which can reach more than 2000 cycles; High charge-discharge rate, that is, large charge-discharge current; Good safety, no problem in bending and puncture at high temperature. The disadvantage is that the energy density is lower, and the same battery life requires more batteries, which correspondingly increases the weight and cost of the car; The consistency is poor, and a better battery management system is needed; The low temperature attenuation is obvious, and the capacity will decrease by about 10% at 0℃ and by about 30% at -20℃.

In winter, the performance of the same car is very different between the south and the north. Mr. Ma Di, a Beijing folk singer, has a surplus of pure electric vehicles in 2000 cycles. Even if Qin has a battery life of only 70 kilometers, 2000 cycles can support Qin1.4000 kilometers of pure electric driving. Including gasoline mileage, it is no problem to cover the service life of the whole vehicle.

Third, what if something really happens? Some friends may think that the car is not finished. What should I do if there is a problem with the battery during its service life? Is it necessary to spend high maintenance fees? First of all, at present, the state requires the key parts of new energy vehicles (batteries, electronic controls and motors) to provide a warranty of not less than 5 years or 65.438+10,000 kilometers, and from 2065.438+06, a warranty of not less than 8 years or 65.438+02 million kilometers. During this period, the maintenance is completely free, and some manufacturers provide a longer warranty period than this, such as BYD, and the battery is guaranteed for life. Then, what if the battery fails after the warranty is issued? Is it necessary to change the battery pack? It really needs to be replaced, but the cost is not tens of thousands of dollars in many people's minds, because there is no need to replace the whole battery.

Just replace the corresponding faulty battery. The most expensive cost of a single battery is several hundred dollars, including working hours, one or two thousand dollars, which should be cheaper than the maintenance of fuel vehicles. At this point, the fear that there will be high battery replacement costs in the use of electric vehicles can be dispelled. We can safely choose a new energy vehicle that suits us, and we don't need to pay any extra fees for the battery during the whole use process, so we can enjoy different experiences brought by new energy vehicles.