Which one is batter, Lithium battery or lead acid battery?

In recent years, with the popularity of the concept of new energy, electric bicycles have become the first choice for thousands of families. According to incomplete statistics, so far, the number of electric two-wheeled vehicles in China has exceeded 3000W, and it is expected that the number of electric two-wheeled vehicles in China will exceed 4000W by 2018. The increase in the number of vehicles has brought about a lot of problems, the first is the traffic problem, a lot of drivers riding electric vehicles do not abide by the traffic rules, resulting in a continuous traffic accidents, the consequences are very serious.

Second is electric vehicle recycling problem, it is well known that electric power is mainly dependent on batteries, and battery cent two kinds of lead acid battery and lithium battery, debate about the advantages and disadvantages of these two kinds of battery never stop, today I will give you analyze, lead-acid battery and lithium battery, who is more suitable for electric vehicles. Before the article begins, let's know what lead-acid battery is and what lithium battery is!

Lead acid battery (VRLA) is a kind of battery whose electrode is mainly made of lead and its oxides, and whose electrolyte is sulfuric acid solution. Under the condition of lead-acid battery discharge, the main component of the positive electrode is lead dioxide, and the main component of the negative electrode is lead. Under charging condition, the main components of positive and negative electrodes are lead sulfate.

A single-cell lead-acid battery has a nominal voltage of 2.0v and can discharge to 1.5v and charge to 2.4v. In the application, 6 single-cell lead-acid batteries are often used in series to form a standard lead-acid battery of 12V, 24V, 36V, 48V and so on

Lithium battery is a kind of battery which is made of lithium metal or lithium alloy as negative electrode material and USES non-aqueous electrolyte solution. Lithium metal battery was first proposed and studied by Gilbertn.Lewis in 1912. In the 1970s, M.S. Willingham proposed and began to study lithium-ion batteries. Due to the chemical characteristics of lithium metal is very lively, so that lithium metal processing, preservation, use, environmental requirements are very high.

Therefore, lithium battery has not been used for a long time. With the development of science and technology, lithium battery has become the mainstream.

Batteries can be roughly divided into two categories: lithium metal batteries and lithium ion batteries. Lithium-ion batteries do not contain metallic lithium and are rechargeable. Lithium metal battery, the fifth generation of rechargeable battery, was born in 1996. Its safety, specific capacity, self-discharge rate and performance-to-price ratio are all better than lithium ion battery. Because of its own high technology requirements, only a handful of companies in a few countries now produce lithium-ion batteries.

Lead-acid battery advantages and disadvantages

Advantages:

The price is cheap, and it also has the property of recycling. After being used out, you can go to the electric car shop to exchange the old for the new, and you can exchange a new set of batteries to make up the price difference, so as to minimize the loss. It is not a small welfare for users. "Fight back" ability is strong, even if the break a little repair can continue to use.

Disadvantages:

Firstly, the volume and weight of lead-acid batteries are very large, and the weight is generally 16-30kg. Secondly, lead-acid batteries generally have deep charge and deep discharge within 400 times, with memory and service life of about 2 years (most cases within 1.5 years). And lead-acid battery contains liquid, battery consumption for a period of time, if the battery is found to be hot or short charging time, you need to add liquid.

Advantages and disadvantages of lithium battery

Advantages:

Small size, light weight, comprehensive comparison of lead-acid battery, lithium battery volume is 2/3 of the volume of lead-acid battery, weight is about 1/3 of the weight of lead-acid battery. Lithium-ion batteries have more capacity than lead-acid batteries of the same size, and weight loss adds about 10% to the battery life of electric cars.

In terms of charge and discharge, lithium battery has a stronger durability than lead-acid battery. When used at room temperature, lithium battery can be continuously charged for 48 hours without accidents such as expansion, leakage and rupture of battery fluid, and its capacity remains above 95%. And under the special charger, you can charge and discharge quickly. Deep charge and deep discharge exceed 500 times, and still do not have memory, average life basically is controlled in 4 to 5 years.

Disadvantages:

Lithium battery production cost is high, the production equipment expensive labor costs accounted for about 40% of the production cost, the price of lead-acid battery is about three times. Moreover, the recycling value of lithium batteries is not high, and the recycling environment in China is also chaotic. Most lithium batteries can only be thrown away or buried in a place when they are used up.

But the inferior lithium battery, in the electric vehicle this kind of sealing condition is not too good, easy to damp lead to poor contact and other reasons may lead to the existence of safety risks.

After the introduction of lead-acid battery and lithium battery battery structure and advantages and disadvantages, the author to give you a detailed calculation of the replacement cost, to see whether the lead-acid battery investment cost is high, or lithium battery investment cost is high.

In August 2017, we launched a cross-evaluation activity for 8 electric cars. In the battery life test, the tortoise of luyuan achieved an average speed of 21.49km/h and a battery life of 59.2km. Its battery capacity is our common 60V20Ah, and the motor power is 800W. We then compared the car's battery capacity and motor power.

Lead-acid battery life:

According to relevant data, in 2015, the average one-way commute distance for Beijing office workers was about 19km, but in 2017, this figure is only much more.

Take the author as an example, my commuting distance to and from work is about 50km in total. If I ride a standard 60V20Ah electric vehicle with a motor power of 800W and commute to and from work at a speed of 30km/h, I can consume one cycle charge and discharge every day.

Calculated according to 21 working days a month, plus the weekends and holidays are scattered broken riding time, the cycle of the electric vehicle charging and discharging within a year, about 300 times and earlier we introduced that the service life of the lead-acid battery in a 400 - cycle recharge, so in the case of such a high frequency cycling, a piece of lead acid battery life up to a year and a half.

Lithium battery life:

Lithium battery usually we contact with a lot of, take the mobile phone as an example, a mobile phone in the use of 1-2 years, although the battery life is not as good as before, but few people will consider changing the battery within two years.

As is known to all, our mobile phones give warning when the battery power is less than 20%. Most people choose to charge their mobile phones at this time. However, we only used 0.8 cycles of charging and discharging from 20% to 100% of charging and discharging.

IPhone4 battery loss

The author found two examples of lithium battery cycle charging and discharging on the Internet. A screenshot shows that an iPhone4 lithium battery with 1420mAh completed 482 cycle charging and discharging, and the remaining battery power of 1147mAh is 20% lower than the factory capacity

The capacity loss of li-ion batteries with different cells after 500 cycles of charging and discharging was measured by li-ion storm

Another is from microblog called "lithium electricity storm", from the comparison of the data to see different types of batteries, lithium batteries after 500 times charging cycle life decay, except one, the rest of the batteries can maintain more than 80% of the excess capacity, lishen lithium iron phosphate is basic no attenuation.

Summary of this paper:

Some people may say that the author's cost theory is slightly flawed. According to the author's inference, although the cost of lead-acid battery replacement has been increased, the battery life of electric vehicles has been revived after each replacement, while lithium battery life has not been replaced, but with the continuous reduction of battery capacity, the battery life is not as good as before.

Although such a statement also has its certain truth, but the economic account that the author wants to calculate to everybody is in electric car still can run normally circumstance, the replacement cost of lead-acid battery and lithium battery.

So, to sum up, if you bought a electric bike for a year only can switch, so the choose and buy the lead-acid battery electric vehicle is a cost-effective, if you don't consider to change, then starting from the second year in a replacement battery, lead acid battery becomes negligible low cost advantage, such as when the third year to replace the battery again, lead-acid battery has a significantly more than the cost of the lithium battery.