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Hybrid What is a battery ？

H V vehicles are equipped with two types of batteries: an "auxiliary battery" to run the engine and accessories, and a "drive battery" to run the drive motor and other components.

Hybrid batteries are currently （ 2023 ） mainly lithium-ion and nickel-metal hydride batteries, with nickel-metal hydride batteries used in Toyota's HV vehicles such as the Prius ・ Aqua, and other batteries in PHV and EV vehicles
and other manufacturers use Li-ion, each with various characteristics.
In any case, drive batteries, like regular batteries, deteriorate ・ over time ・ due to wear and tear ・ and physical factors, and therefore need to be replaced and repaired periodically.
In addition, unqualified replacement repair is not allowed due to the very high voltage of the drive battery cells.

What are nickel What is a hydrogen battery?

A nickel-metal hydride (Ni-MH™) battery is a secondary battery that can be charged and discharged.
Because of its relatively low environmental impact and larger capacity per mass than nickel-cadmium or lead-acid storage batteries, it has become increasingly popular, and nickel-metal hydride is still used in most rechargeable household batteries.

Since charging and discharging is done by the inter-pole transfer of hydrogen atoms, they have a higher service life compared to nickel-cadnimium. However, overcharging deteriorates performance, so care must be taken not to overcharge or discharge near the limit.
Also, due to its structure, when over-discharged or when a large current flows, gas is generated inside the battery, so the battery is equipped with a release valve, which may cause the electrolyte inside to leak out at the same time. 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 is extremely high ・ or low. However, compared to lithium-ion batteries, nickel-metal hydride batteries are more resistant to temperature fluctuations, especially at low temperatures.

This battery also has a self-discharge effect and discharges even when not in use, but recently, some batteries have been developed that have almost no self-discharge.
Currently, Toyota HV vehicles that use nickel metal hydride batteries are recommended to be driven for about 30 minutes or 16 km at least once every 2 ～ 3 months, as they gradually discharge even if the vehicle is left unused for a long time.

What is a Li-ion battery ？

Li-ion （ Li-ion ） battery is a rechargeable battery that Dr. Akira Yoshino helped develop, for which he was awarded the Nobel Prize in Science in 2019 Dr. Yoshino was awarded the Nobel Prize in Science in 2019 for his achievements.
Its most important feature is that no scientific changes occur during charging and discharging, and it is established solely by the transfer of lithium ions between electrodes.
＊ In addition, the button battery （ and primary battery ） called "lithium battery" are different

This battery has the feature of slow deterioration and long life compared to other batteries because no chemical change occurs during charging and discharging.
It is also known that there is very little degradation due to the number of charge/discharge cycles. Also, the nominal voltage V is high and the output vs. mass value is extremely high, and is currently used in many EVs and other vehicles.

However, lithium-ion batteries also have drawbacks. They are expensive, and the main reason for this is the amount of resources available. As mentioned above, they are susceptible to temperature changes, and the most dangerous thing is that they can catch fire at high temperatures. The cause of ignition is the electrolyte, which is extremely flammable and difficult to extinguish once it starts to burn.

Therefore, shocks that cause liquid leakage ・ at high temperatures ・ and internal shorts due to lack of quality control are safety issues, especially for foreign-made products.
Also, there is a drawback that it cannot be recharged when the voltage drops due to over-discharge, and it must be said that the product is still incomplete.

About battery life

How does a battery generate electricity in the first place ？ Simply put, it is a chemical reaction.
Therefore, the reaction is slow at low temperatures and active at high temperatures, and if it goes too far, it will ignite.
The reaction rate varies with ambient conditions.
The only thing is that the chemical reaction between nickel and lithium used in HV cars is representative of a reaction that can be repeated, called a rechargeable battery, and like the one-time reaction of a manganese battery （ or primary battery ） it basically decreases with use, not infinitely. It is not a chemical reaction that repeats itself indefinitely. In other words, the life of a battery is a gradual slowing down of the reaction and the inability to produce the required amount of electricity. The battery life is defined as the time when the reaction becomes too sluggish to produce the required amount of electricity, or when it can no longer be recharged. The length of battery life depends on the frequency of use ・, temperature changes ・, and individual battery characteristics.
（ The number of cycles is a measure of how many times a battery can be charged and discharged up to 0 ～ 100%.
For example, 0 ～ 1 time at 100% charge/discharge 50 ～ 90% ＋ 30~80% ＋ 1 time at 70~80% ）

As of May 2023, domestic makers are required to provide 5-year 100,000 km warranty period. However, there are many cars that have been running for more than 10 years and 200,000 km and have never shown an error message, so it seems that the life of the drive battery cannot be generalized.

If you are looking for a drive battery for your hybrid car ！