12V lead-acid battery has been on fire for nearly 70 years, but it is irreplaceable! Can we fight for another half a century?
Are 12V lead-acid batteries irreplaceable?
Invention of the lead-acid battery
In the southern half of the back of the moon, there is a large meteorite impact crater formed about 3.9 billion years ago. In 1970, it was named "Plant Crater", also known as "Plant Crater".
The crater is named after the French physicist Raymond-Louis Gaston Planté (1834-1889), the inventor of the lead-acid battery who made outstanding contributions to the modern automobile industry.
Gaston Prandtl is a genius. He studied at the Sorbonne for his undergraduate degree. At the age of 16, he received a Bachelor of Arts degree, a Bachelor of Science degree at the age of 19, a Master of Science degree at the age of 21, and he became the National School of Arts and Crafts in Paris at the age of 26. Professor of Physics.
Is it amazing to be a physics professor at 26? No, because Gaston Prandtl invented the lead-acid battery at the age of 25. The commercial rechargeable battery he invented was on the car invented by Mr. Karl Benz in the future, and got promotion on a global scale.
It is normal for feats higher than the sky to be engraved on the moon.
Promotion of lead-acid batteries
Lead-acid batteries are "a" secondary battery and "first" secondary battery, because the secondary batteries before the lead-acid formula were not officially mass-produced, and the lead-acid formula was improved by French chemists to achieve After mass production, the lead-acid battery improved by the Luxembourg engineer, inventor, and entrepreneur Henry, which was produced by a large-scale enterprise, took 5 years and 2 months to be scrapped, which solved the problem of the short life of the secondary battery.
The first thing after the mass production of lead-acid batteries is to provide temporary lighting power for the train bodies that stop at the railway platform. At the same time, a considerable part is also used to manufacture electric vehicles.
Before the mass production of secondary batteries, all electric vehicles are experimental products, because the primary batteries they use are scrapped when they are exhausted. The arrival of lead-acid batteries announced the birth of power batteries, because it can really drive a car for tens of kilometers.
In 1918, AMC brought 6V voltage into the mass production car assembly sequence, and gradually gave birth to the assembly of on-board lights and on-board starters, and the production of lead-acid batteries began to increase. After entering the 1950s, the large American V8 engine with a displacement of 6-8L put a heavy load on the 6V voltage system. The engineer connected two 6V lead-acid batteries in series to become a 12V lead-acid battery, which has been used until now.
Of course, 12V is not the only voltage for lead-acid batteries. The diesel engines of some heavy-duty vehicles are very large and heavy. You can connect two 12V batteries in series to become 24V batteries, or you can connect three series to become 36V batteries.
The principle of lead-acid battery
Why are lead-acid batteries only used to drive golf carts and not powertrains for passenger cars?
The reason is that the energy density of lead-acid batteries is very low. Even after a century and a half, the current lead-acid batteries can only achieve about 35-40Wh/kg (about 80-90Wh/L), which is too heavy and has too little power. .
Take our commonly used 12V lead-acid battery as an example, the capacity is only 0.6-1.2kWh (generally more than 1kWh is used for medium and large vehicles of luxury brands), and the output power is only 5kW (of course, there are also more than 10kW cold start power), start The gasoline engine is enough, and you can listen to music in the car for more than half an hour, but the air conditioner can only last for dozens of seconds before the compressor stops, because this is not a deep cycle battery.
The industrial chain of lead-acid batteries is extremely mature and the structure is very simple. In a fully charged state, the negative plate of a lead-acid battery is lead, the positive plate is lead dioxide, and the electrolyte solution has a relatively high concentration of aqueous sulfuric acid, which stores most of the chemical energy.
If it is overcharged, part of the water will be electrolyzed into oxygen and hydrogen. At this time, it must be refilled with pure water to replenish the electrolyte.
During discharge, both the positive and negative plates will become lead sulfate (II) (PbSO4), the electrolyte loses sulfuric acid to obtain water, and electrical energy is released.
The lead-acid battery is full of liquid, has high density, heavy weight, and high energy density, but its stability is particularly good, the number of cycles is large, the global industrial chain is mature, and the cost is relatively low, so it is used in many industries, such as :
1. Starter battery: used in the starter part of the car, it is lighter than the deep cycle battery of the same size, and has a longer service life, generally lasting 3-5 years.
2. Power battery: Two-wheeled and three-wheeled electric vehicles are preferred. The new national standard stipulates that four-wheeled electric vehicles should use lithium batteries, in addition to golf carts, electric forklifts, etc. The power battery must be a deep cycle battery, and the energy storage potential must be tapped.
3. Energy storage battery: The energy storage battery used in RVs and ships is designed to have a larger capacity than the starting battery, but it is not as deep as the deep cycle battery charge and discharge, and the life/energy storage is in between.
4. Backup power supply: Uninterruptible power supply UPS, communication base stations, and alarms also use lead-acid batteries as energy storage, which are gradually replaced by lithium-ion batteries. This kind of battery is very important to the number of cycles, and the longer the life, the better.
Emission-free electric vehicles are still a little far away (not the main sales volume for the time being). The most feasible energy-saving and emission-reduction solution is the engine self-start-stop technology, which corresponds to the new 12V lead-acid battery - EFB battery (Enhanced Flooded Battery) and AGM battery (Absorbent Glass Mat Battery).
EFB is an enhanced flooded lead-acid battery
There is no essential difference between the structure and the old lead-acid battery. The old battery mentioned here refers to the SLI battery (Start Lighting Igniton) and the AMG battery (Alternator Management System), both of which are not compatible with the automatic start-stop system.
When you buy medium and large vehicles, luxury brand models, performance models, etc., you will find an AGM battery placed in the cabin. AGM stands for "Absorbent Glass Mat", which uses a glass mat Separator that absorbs acidic solvents and prevents leaks.
EFB and AGM are the products of two different processes for starting wet batteries, and the principle is the same. When fully charged, the open circuit voltage is generally around 12.8V, and if it drops below 12.4V, it will automatically charge.
Compared to EFB batteries, AGMs are chemically more active and can withstand higher frequency self-start-stop and high inrush currents from kinetic energy recovery systems.
Can I change the AGM for a car that comes standard with EFB?
The answer is: it can be used temporarily, but it will age faster.
Let's first understand the difference between EFB and AGM lead-acid batteries:
1. AGM is currently the strongest civilian 12V battery technology, and the price is about 1.5 times that of EFB batteries.
2. The theoretical life of AGM is 4-6 years, and the theoretical life of EFB is 3-5 years. If the lead-acid battery is designed in the rear compartment (front engine solution), because there is no engine to bake at high temperature around the clock, the life will be longer.
3. AGM has no acid leakage, stronger cold start function and stronger high current surge tolerance.
Lead-acid battery Some FAQs
How long will the 12V battery generally run out of power?
This indicator tests the self-discharge rate of the lead-acid battery, that is, the charge retention ability.
In theory, the self-discharge rate of lead-acid batteries is between 20-30%, that is, between 20-30% in a month, but in practice it is far more than this ratio.
What are the signs that lead-acid batteries are dying?
1. The engine ignition is weak, and it is even lit a few times.
2. Press the horn without starting the engine, the sound is weak.
3. Some instruments have battery warning lights, and some display battery voltage.
Do 48V mild hybrids still need 12V lead-acid batteries?
Yes, all 48V light-hybrid vehicles currently require 12V lead-acid batteries.
Do new energy vehicles still need 12V lead-acid batteries?
Yes, even pure electric vehicles also need 12V lead-acid batteries.
Does the ancient lead-acid battery have a future?
1. Previously, some racing vehicles used 12V lithium batteries to replace heavy lead-acid batteries, and now some civilian vehicles have begun to use lithium batteries instead. For example, BYD DM-i hybrid uses self-produced 12V lithium iron phosphate batteries, weighing only 2.2 ±0.2kg.
2. The industrial chain of traditional 12V lead-acid batteries is very complete and cost-effective. Even if they are gradually retired from vehicles, they can continue to be used on non-mobile platforms, and their industrial scale is in decline.
3. The task of reducing the weight of lead-acid batteries is extremely difficult to achieve. The skills of this technology tree have been fully filled. The next thing to do is to replace lead-acid with lithium-ion batteries.
4. The advantage of the lead-acid formula is that the thermal runaway is very low, and very few vehicles spontaneously ignite due to the thermal runaway of the lead-acid battery. In addition, the working temperature of lead-acid batteries is as wide as -20℃-60℃, which is unmatched by most current lithium batteries.