Why are more and more new car batteries starting to use lithium batteries instead of lead-acid batteries?

Electric cars point north

2024-05-06 00:03Published in Shandong

Many car owners may not realize that the "battery" on your new car is also the starting power supply we often say, which may no longer be a lead-acid battery but a lithium battery.

For example, the BYD Qin PLUS DM-i and Destroyer 05, which are the most popular now, both use BYD's self-developed lithium iron phosphate starting batteries, and these two cars sold more than 80,000 units in April, in addition, Tesla, Weilai and other brands also use 12V ternary starting batteries provided by CATL.

At the Beijing Auto Show, the author also saw the 12V lithium battery for vehicles provided by Bosch, and it can be said that it is the general trend for lithium battery batteries to replace lead-acid battery batteries.

So what are the advantages of lithium battery starting battery?

Advantages of lithium battery starting battery

I believe that the old drivers should have several times to change the battery experience, the traditional lead-acid battery with a 3-5 years or so to replace, improper use, such as going home at night without turning off the headlights, may be replaced in a year or two.

This is to say that the first advantage of lithium battery is long life.

The cycle life of lead-acid batteries is generally only 300-600 times, and now the cycle life of new ternary lithium batteries is generally more than 1500 times, and lithium iron phosphate is easy to reach more than 2500 times, and the life is 5-10 times higher than that of lead-acid batteries.

The second major advantage of lithium battery batteries is weight and volume.

At present, the general lead-acid battery starter battery weighs 15-20kg, and according to a "starter iron battery" shown in the picture above, the weight is only about 2.2kg (the ternary battery will be a little lighter), almost one-tenth of the lead-acid battery.

As for the volume, it is not much, and the lithium battery starting battery is generally less than half of the lead-acid battery.

The picture above is a comparison between the 48V lithium battery of the Tesla Cybertruck and the 12V lead-acid battery of the Ford BRONCO taken by overseas netizens, Tesla's weighs only 2.2 kilograms, and the Ford off-road vehicle weighs 23.3 kilograms, which is more than 10 times that of Tesla, and the volume is much larger.

Finally, there is a very critical point, the charging and discharging efficiency of lithium batteries is higher and the loss is smaller.

At present, the charging and discharging efficiency of lithium batteries can exceed 97%, while lead-acid batteries are only about 80%, the loss of lead-acid batteries is very serious, if the high-voltage battery inputs 1Kwh of power to the start-stop battery, the lead-acid battery can only output 0.64kWh of power, and the lithium battery can output 0.94kWh of power,

This is not obvious in the impact of fuel vehicles, after all, from the point of view of the most power-intensive air conditioning on the car, the air conditioning of fuel vehicles is directly driven by the engine in summer, and the "waste heat" of the engine can be used in winter, but it is very critical in new energy vehicles, and the electricity of small batteries on new energy vehicles basically comes from large batteries, and if the efficiency is too low, it will obviously affect the mileage.

In addition, the self-discharge of lead-acid batteries is also much higher than that of lithium batteries, which means that if the vehicle is left for a month, the remaining power of the lead-acid battery will be significantly less. This is unacceptable for new energy vehicles where all the energy of the whole vehicle comes from the high-voltage battery pack, because the starting battery power is low to a certain extent when it is stationary, and the high-voltage battery pack will charge it. The energy consumption of such lead-acid batteries is much larger than that of normal batteries, which further affects the energy consumption of the whole vehicle and reduces the battery life of the vehicle.

Disadvantages of lithium battery starting battery

The three advantages of lithium battery starter batteries have been mentioned above, but lead-acid batteries have been invented and commercialized for more than 100 years, and are still used in most cars, so they naturally have their own advantages.

The first is the price, at present, the price of a 12V lead-acid battery ranges from 200-500 yuan, while the lithium battery starting battery of the same capacity is about 1500 yuan (Tesla's replacement price is about 1600 yuan), the price has directly increased several times, which is not the power to replace the very "buckle" manufacturers, the European BMW X3's high-end starting battery is a 12V 10AH lithium battery, more than 500 euros, and the low-profile model is a lead-acid battery.

For consumers, it is actually okay, the life of lithium batteries is longer, from the perspective of the entire life cycle of the car, the cost is about the same, and even with the further reduction of lithium battery batteries, it is cheaper.

The second disadvantage is that the working temperature of the lithium battery is more picky, the lithium battery is easy to thermal runaway at high temperature, and the performance of the lithium battery will be greatly reduced at low temperature, while the performance of the lead-acid battery is relatively stable, and it can work at minus 40 degrees, and the lead-acid battery is also very stable at high temperature, without the risk of thermal runaway of the lithium battery.

In addition, the discharge rate of lead-acid batteries is also relatively high, which can be continuously discharged at a rate of 5C, and the instantaneous current can reach more than 200A, but lithium batteries have also caught up with technological progress in this regard.

It is the general trend to replace lead-acid batteries with lithium batteries

After talking about the advantages and disadvantages of lithium batteries and lead-acid battery starter batteries, we can find that in traditional fuel vehicles, the advantages of lithium batteries are not large, and lead-acid batteries are better and cheaper, but in new energy vehicles, the advantages of lithium batteries are infinitely magnified, and the front cabin space can be saved if the size is small. The key point is that the charging and discharging efficiency of lithium batteries is high, which will obviously affect the core indicators of new energy vehicles, energy consumption and battery life.

Of course, the requirements for starting the battery with a lithium battery will be much higher, especially for the BMS system of the battery (the lead-acid battery does not need the BMS system) and the overall thermal management system of the vehicle has very high requirements, so that the lithium battery always works at a more suitable temperature, and always works under a more suitable SOC, etc.

In the first two weeks of April, the penetration rate of new energy vehicles has exceeded 50%, and we will find that the arrival of the era of new energy vehicles is not only the form of power has changed, but also the sales model (dealers have become direct), intelligent, marketing and other aspects have changed, and the replacement of lead-acid batteries with 12V lithium batteries is only one of the small microcosms, and perhaps the 12V low-voltage system will be replaced by the 48V system in the future.

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