In 1918, the predecessor of AMC, the Hudson Motor Company (Hudson Motor Car Company), brought 6V voltage into the mass production car assembly sequence, and gradually gave birth to the assembly of on-board lights and starters, and the production of lead-acid batteries began to increase.
After entering the 1950s, the American large V8 engine with 6-8L displacement was unaffordable for the 6V voltage system. Budget engineers connected two 6V lead-acid batteries in series and became 12V lead-acid batteries, which have been in use ever since.
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 24V batteries, or three in series to 36V.
The energy density of lead-acid battery is so low that even after a century and a half, the current lead-acid battery 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, for example, the capacity is only 0.6-1.2kWh (large cars in general luxury brands use more than 1kWh), the output power is only 5kW (of course, it also has more cold start power than 10kW), it is enough to start the gasoline engine, you can listen to music in the car for more than half an hour, but the air conditioner can only last a few seconds to shut down the compressor, because this is not a deep cycle battery.
The industrial chain of lead-acid battery is very mature and its structure is very simple.
In the fully charged state, the negative plate of lead-acid battery is lead, the positive plate is lead dioxide, and the electrolyte solution has a high concentration of sulfuric acid aqueous solution, in which most of the chemical energy is stored.
If overcharged, part of the electricity will be decomposed into oxygen and hydrogen, and the electrolyte will have to be refilled with pure water.
In the past, cars had only tape drives and radios, and even so, it was often necessary to carry spare batteries to prevent weak car batteries from falling off the chain.
After entering the 21st century, the electrical equipment on the new car (including audio-visual entertainment system, active safety system, seat heating and massage, etc.) has increased sharply, and the engine self-start and stop system has gradually become the standard item of the mainstream passenger car. The 12V battery must also be upgraded synchronously to adapt to this era.
Of course, 12V lead-acid batteries have changed since the 1990s. In the past, the car battery only needed to start the heat engine without doing a lot of work, but now the 12V battery has to deal with the self-start-stop condition in the congested urban environment. Turn off the engine at the right time, such as when waiting in line at the red light, or the vehicle with taxiing function is turned off before reaching the red light, which can improve the thermal efficiency of the heat engine, save fuel and reduce emissions to a certain extent.