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​ハイブリットピット千葉

​What is a hybrid battery?

　HV vehicles are equipped with two types of batteries: the auxiliary battery that operates the engine and accessories, and the drive battery that operates the drive motor.

　Hybrid batteries are currently (2023) mainly lithium-ion batteries
Nickel-metal hydride batteries are used, and Toyota's HV vehicles represented by the Prius Aqua are nickel-metal hydride, PHV vehicles, EV vehicles, and other manufacturers use lithium-ion batteries, each with its own characteristics.
　In any case, like normal batteries, drive batteries deteriorate and wear out due to time, consumption, and physical factors, so they need to be replaced and repaired regularly.

　In addition, because the drive battery has a very high voltage, it is not permitted to replace or repair it without qualification.

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​What is a Ni-MH battery?

​ 　A nickel-metal hydride (Ni-MH) battery is a secondary battery that can be charged and discharged. Nickel-metal hydride batteries are widely used because they have relatively little impact on the environment and have a larger battery capacity per unit mass than nickel-cadmium and lead-acid batteries.

　Since charging and discharging are carried out by the movement of hydrogen atoms between electrodes, it has a longer life than nickel-cadmium. However, over-discharging and over-charging will degrade the performance, so be careful not to over-charge or discharge to near the limit.
​ 　In addition, due to the structure, gas is generated inside the battery during overdischarge or when a large current flows. phenomena may occur.
　This liquid is toxic and dangerous if it enters the body.
　
　Nickel-metal hydride batteries, like other batteries, are characterized by a decrease in power generation efficiency when the ambient temperature rises or falls extremely. However, compared to lithium ions, it is more resistant to temperature changes, and is particularly superior at low temperatures.

　In addition, this battery also has a self-discharge function, and it will discharge even if it is not in use, but recently, it seems that batteries with almost no self-discharge have been developed.
　At present, Toyota HVs that use nickel-metal hydride batteries discharge little by little even if the vehicle is left for a long time.　 Recommended.

​What is a lithium-ion battery?

　Lithium-ion (Li-ion) battery is a secondary battery developed by Dr. Akira Yoshino, who won the Nobel Prize for Science in 2019 for his achievements.
　Its greatest feature is that no chemical change occurs during charging and discharging, and that it is established only by the movement of lithium ions between electrodes.
　*Please note that the button battery (primary battery) called "lithium battery" is a different product.

　Since this battery does not undergo chemical changes during charging and discharging, it is characterized by slower deterioration and longer life than other batteries, and it is known that deterioration due to the number of charging and discharging is extremely small compared to other batteries.
　In addition, the nominal voltage V is high and the output to mass value is extremely high, so it is currently used in many EV vehicles.

　However, lithium-ion batteries also have their drawbacks.
Being expensive The biggest reason is the amount of resources.
　 Also, as mentioned above, it is vulnerable to temperature changes and is especially dangerous when it ignites at high temperatures.
　The cause of ignition is that the electrolyte is extremely flammable.

　Therefore, there are safety issues such as shocks that cause liquid leakage, high temperature, overcharging, and internal short circuits due to lack of quality control, so be careful especially with foreign-made products.
　In addition, it has the drawback that it cannot be recharged when the voltage drops due to overdischarge, so it must be said that it is still incomplete.

​About battery life

​ 　How does a battery generate electricity in the first place? Simply put, it's a chemical reaction.
　That's why the reaction slows down at low temperatures, becomes active at high temperatures, and ignites if it goes too far.
　Ambient conditions change the reaction rate.
　The chemical reaction between nickel and lithium used in HV vehicles is representative of secondary batteries that can cause repeated reactions. Basically, the more you use it, the less it will be. It's not a chemical reaction that repeats infinitely.
　In other words, the life of the battery means that the reaction gradually becomes dull and the necessary amount of electricity cannot be produced.
Or when the charging reaction stops happening, that's the life of the battery.
　As for the length of life, which is a concern, there are individual differences in frequency of use, temperature changes, and individual batteries, so it is not possible to generalize. Nickel hydrogen is said to be cycled 1,200 to 2,000 times, while lithium ion is said to be 6,000 to 12,000 times.
　(The number of cycling times is a measure of how many times the battery can be charged and discharged from 0 to 100%. For example, once at 0 to 100% charge and discharge, once at 50 to 90% + 30 to 80% + 1 time at 70 to 80%)
　As of May 2023, domestic manufacturers have issued a warranty period of 5 years/100,000 km for drive batteries.
　However, it seems that there are many cars that do not display an error message even after running for more than 10 years or more than 200,000 km.
　It seems that the life of the driving battery cannot be said unconditionally.

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