Why Do Batteries Get Heated?

In this article, we explain why batteries get heated and why they need a thermal management system in a battery management system.

So batteries are not perfect devices and are not perfect conductors.

Within every battery there is some internal resistance due to the chemical composition of the battery.

Resistance opposes the flow of current, which is displayed in ohms law, I= V/R.

Current is the flow of electrons.

Resistance opposes this flow of electrons and creates friction. This friction produces heat as a byproduct.

Due to there being no perfect conductor, every battery is going to have at least internal resistance. This is resistance within the battery itself.

The best batteries have the lowest internal resistance. For a lithium ion battery, the internal resistance may be as low as 5 mOhms, or 0.005 ohms. The lower the internal resistance, the better, because the less heat is generated. This causes less heat buildup in the battery system and reduces the chance of overheating and reduces the need for higher amounts of cooling.

Lithium ion battery have internal resistances that range in value from 5-30 mOhms.

The heat produced by the battery is equivalent to I squared * R. This is shown in the following formula, H= I²R, where I is the current passing through the battery and R is the internal resistance of the battery.

So this heat created by the product of current passing through this internal resistance of the battery can increase the temperature of a battery system.

This is the reason in a battery management system, we must have a thermal management system in order to make sure the battery system remains cool and does not overheat.

The thermal management system may utilize various techniques to keep the battery system cool, including utilizing a heat sink, air cooling, liquid cooling, or thermo electric peltier cooling.

Again, this is all due to the fact that batteries cannot be manufactured as perfect conductors. Even the best batteries created will have at least a few mOhms of internal resistance. This internal resistance creates friction when current (electrons) pass through it, generating heat. Due to this, any battery management must monitor the temperature of the battery system and have thermal management techniques in place to prevent overheating. s

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