Tesla is into Lead-acid Batteries
More than 100-year-old lead-acid batteries are old but still carrying the latest electric cars. Although Tesla’s Musk wants to replace it countless times, is there an alternative?
Electric bicycles are low-speed vehicles and are the first in China. The number of electric bicycles is close to 300 million, and the annual output value exceeds 100 billion yuan, setting the "world's first". Although Phoenix high-end products represented by lithium-ion electric bicycles have recently begun to sell in Europe, most of these low-speed electric bicycles still use lead-acid batteries. Why not use a lighter and smaller lithium battery?
Tesla is certainly not a low-speed electric vehicle. In addition to the 900 kg "ballast stone" power battery pack installed on the chassis between the front and rear axles, there is also a 12V lead-acid battery that people can hardly see. In fact, hybrid or plug-in hybrid vehicles are still powered by the same lead-acid batteries as fuel vehicles. Regardless of the type of vehicle, if the battery is severely depleted for a long time, the vehicle will still not catch fire.
It seems that this ancient lead-acid battery is still indispensable! In fact, Musk has long wanted to replace it...today I will talk about why lead-acid batteries with a history of more than 100 years are still equipped with a new generation of electric vehicles? Is there an effective alternative?
01 Why do pure electric vehicles need lead-acid batteries?
In 1860, Frenchman G.Plante invented lead-acid batteries. It was not until the advent of DC generators 13 years later that lead-acid batteries were gradually put into practical use. Since 1910, automobile batteries have been used for starting, lighting, and ignition, enabling the development of lead-acid batteries; the telephone industry has also begun to use lead-acid batteries as a safe, reliable, and backup power source that can be used for many years. Until today, lead-acid batteries are widely used in automobiles, motorcycles, railways, mining, communications and other fields.
The reason why lead-acid batteries have not been replaced by lithium batteries is: lithium batteries are complicated to manufacture, cost two or three times that of lead-acid batteries, and the ex-factory price is more expensive; lead-acid battery technology is more mature and has better stability.
So why is Tesla, which is not bad at money, also using lead-acid batteries? Take Model X as an example, look at this 12V lead-acid battery that is the same as a traditional fuel car.
As seen in the user manual, Model X will also fail to start due to battery failure. This is not necessarily a problem with the lithium battery pack, but just the battery is dead.
Battery failure identification for Model X and fuel vehicles
The battery is dead → unable to open the door/cabin cover/charging cover → unable to pick up power → unable to start the vehicle; the same is true with APP/key, unable to enter the car... Is there a physical unlocking method for the owner to enter the car? Searching on the Internet for "How do I open the door if Tesla has no electricity?" It's strange! All pages are the same-404!
"How can Tesla open the door without electricity?" No solution
However, I found an article that introduced a method for rescue: pull the two wires in the towing hook hole, the cabin cover will open (risk of theft), and the car will sound an alarm. After opening, charge the battery or power up, and the door can be opened. As for the old model, the old driver said that he had to open the entire black net to see the "mechanism" that could open the front trunk. It seems that it is really not easy to start Model X by powering on. Here, suppose you can open the engine compartment cover, and then you can see the front trunk for storage (no other pure electric vehicles, and there are mixed reviews). Remove the cover above it to see below the brake fluid replenishing port. The battery and the positive and negative terminals. It seems that in Model X, the role of the battery is the same as that of a fuel car.
The Model X battery is under the front trunk cover
It's a bit far off, get back to business.
The lead-acid battery is a weak current battery, which is normally charged by a lithium battery. It is mainly used to provide power for the normal use of on-board electronic equipment before the engine (fuel vehicle) or power battery is not powered, such as remote control key recognition, vehicle unlocking and The large-screen display of the instrument is the same as the principle of battery power supply for ordinary fuel vehicles. Under normal circumstances, the power battery is connected to the 12V battery. If the battery loses power, the power battery can charge it.
In other words, the high-voltage power battery must have a low-voltage power supply to cooperate. Experience tells us that when you start a car with the radio on, the radio will be cut off at the moment the engine is ignited, and the lights are like this. Explain what? Think about it for yourself.
Then why this small power supply must be a 12V lead-acid battery instead of a 12V lithium battery? In addition to the above-mentioned cheapness, there are the following reasons:
①Low temperature power output characteristics: it can start smoothly even at minus 20℃, with high reliability;
②The supply chain cost is low: 12V lead-acid battery technology is mature and there are many suppliers;
③Easy to repair and replace: no special product is required.
The disadvantage is that the shape, volume and weight are larger than lithium batteries, but a car only needs a battery, not as many as power lithium batteries.
02 Go beyond lithium batteries to create a new path
In order to improve fuel efficiency and reduce dependence on oil, the automotive industry is facing increasing pressure, and electrification is an inevitable trend. The premise is that the solution must be able to meet the strict requirements for high performance, reliability and safety.
There is a technology that can provide high power density, safety and service life, and can be as stable and reliable as lead-acid batteries. It is a super capacitor (also known as an electric double-layer capacitor), which is ready for the development of today's hybrid and electric vehicles. Supercapacitors can be connected in parallel with batteries to take advantage of energy density and power density to create a more efficient and robust complete electrical system.
Let’s first look at the places where supercapacitors are inferior to lithium batteries: Lithium batteries and supercapacitors are like marathon runners and sprinters. The former can provide a long-term stable discharge during long-distance driving; the latter has less endurance and can only be used in short Time releases a lot of energy.
As a backup power source, the advantages of supercapacitors are: safety and reliability, no smoke, no flame, maintenance-free for life, and no need to oversize, no need to leave a replacement space like a battery.
03 Application scenarios of super capacitor replacement
Can supercapacitors replace traditional lead-acid batteries? The following application scenarios can illustrate the problem.
12V start-stop application
Battery degradation can cause the engine to start unsmoothly; higher ESR (equivalent series resistance) will reduce battery life; frequent start-stop cycles will reduce battery performance; low temperature will also limit its function.
When the engine starts, it needs to provide instantaneous high current. We install the super capacitor between the battery and the starter, which means that the battery is disconnected from the starter. As the engine start module, the super capacitor always provides starting power for the engine, while the battery only needs to provide energy for lights, air conditioning, heating, etc. Supercapacitors have the lowest ESR and the highest power density in the industry, can ensure a longer service life, are suitable for fast starting, and have a full power performance of -40 to +65°C, which is more suitable for this "one hammer" scenario.
Start and stop the application
The mass energy of lead-acid batteries is 32-37Wh/kg, and the U.S. standard is 41Wh/kg; and the third-generation supercapacitors that are currently close to mass production are more than 60Wh/kg, which are suitable for use on fuel vehicles and xEV platforms.
EPS and Electronic Brake (EBS)
Ni-MH and Li-ion batteries do not have operating signals that can be used for reliable characterization in the "normal state", so it is difficult to determine SOH (state of health) and SOF (state of function). The super capacitor is suitable for use as an auxiliary energy source.
Regenerative braking energy absorption
Fast discharge is not the only advantage brought by supercapacitors, it can also be charged faster (within 15 seconds), which is the most reliable technology.
The current solution uses hydraulic pressure or battery to absorb regenerative energy. Because it is a sporadic operation, the average power demand is greater than the peak value of 1kW and greater than 300W, and requires a rapid charge and discharge cycle. It is easy to cause the regenerative energy to be unable to absorb and cause transients. The low resistance of the super capacitor can ensure low self-heating during operation and improve reliability.
The current solution is to use a three-way catalytic converter to burn fuel to heat the exhaust gas. An average of 3kW power is required for 30 seconds, which is activated once every KL15 (engine ignition signal) cycle. In a cold car, the battery cannot meet the performance requirements. Supercapacitors have excellent low-temperature power performance and are very suitable for this scenario.
Braking energy regeneration
The rapid charge-discharge cycle of lead-acid batteries (EFB or AGM type, with different materials) requires more than 3kW peak and more than 200W average power. Because it is installed in the engine compartment, the battery life is generally not more than two years; at lower temperatures, the battery has poor charging acceptance and is too large. Supercapacitors have excellent power performance and charge acceptance at lower temperatures, are not affected by charging throughput, are maintenance-free, and are more suitable for this scenario.
04 Super capacitor innovation accelerates the electric car revolution
Super capacitor manufacturing
Electric vehicles need devices to store electrical energy. Both batteries and supercapacitors have this function. The battery charges relatively slowly and discharges slowly. Supercapacitors charge quickly and discharge quickly. Batteries can store a lot of energy, and supercapacitors are the best choice for small amounts of energy. After all, batteries are better than supercapacitors in some aspects, and supercapacitors are better than batteries in some aspects.
Super capacitor and battery comparison
In the next few years, supercapacitors may replace all current lead-acid batteries used in electric vehicles to store electricity required for daily functions (operating door locks, providing internal lighting, etc.). They also help electric vehicle OEMs do what they do best-fast charge and discharge, while allowing the main power battery (lithium battery) to do what it does best-allowing the car to travel farther on the road.
Bloomberg New Energy Finance and Energy Storage Analyst James Frith said: "Over the years, people have been interested in supercapacitors. The problem is that the price of lithium batteries has dropped rapidly. However, there are definitely many areas in the automotive market where the latter can be found. application."
He hinted that Musk also loves supercapacitors. Tesla’s self-developed new battery will be a combination of dry battery technology and supercapacitors. If it is used in its products, then supercapacitors will definitely become part of the future electric transportation field. The field is improving almost every day.
According to reports, Skeleton Technologies has been working hard to develop advanced supercapacitors that can replace traditional automotive lead-acid batteries. CEO Taavi Madiberk admitted that supercapacitors do not have the same energy density as lithium batteries, but he believes that the technology has been improving. At present, the energy density of its products has reached 60Wh/L per liter. He said: "We are already in discussions with several car OEMs, and they all want to get rid of the bulky lead-acid batteries in cars."
"Sometimes people think that lead is a past problem because it is related to internal combustion engines, but in fact all electric cars have 12V lead-acid batteries," he said. "We are studying a viable alternative to replace all lead-acid batteries."
According to reports, in 1999, the price of lithium batteries per kilowatt-hour was about 5,000 US dollars, and now it is less than 200 US dollars; and Tesla’s current battery price may be below 100 US dollars. The cost of supercapacitors will experience a similar rapid decline.
According to TechExplorist, scientists at University College London and the Chinese Academy of Sciences have developed a new type of flexible graphene supercapacitor that can be safely charged at high speed, accumulate record-breaking energy, and can be stored for a long time.
New flexible graphene supercapacitor material
The new supercapacitor uses an innovative multilayer graphene electrode that can be bent 180 degrees without loss of performance and does not require a liquid electrolyte, thereby minimizing the risk of explosion. The energy density of the prototype battery developed by the research team is 88.1Wh/L per liter. In addition, the scientists claim that their invention has a power density of 10,000W per liter and can maintain 98.7% of its capacity after 5000 charge-discharge cycles.
Write at the end
Automobile is a harsh environment, including potential risks such as extremely wide temperature range, mechanical vibration, noise, gas pollution, and transient voltage and high current. These are the important factors that affect the stability, reliability and driving experience of modern cars. It is said that the European Space Agency (ESA) has conducted supercapacitor tests in the harsh space environment and believes that it is more severe than the car environment.
Let's look at what super capacitors mean to cars? Reliable start, reduced fuel consumption (or main battery power consumption), extended battery life, barrier-free one-time investment, small size, light weight, and easy installation. And these seem to be enough!