Why a Mobile Phone Battery Has More Than Two Terminals?

Last updated on March 22nd, 2024 at 04:11 pm

Hi! If you are reading this then you must have been using a mobile phone for a very long time. But have you ever considered the fact that your mobile phone battery has more than two terminals? Yes, some have 3 terminals and some have 4. And in this article, we are going to learn exactly why.

Why a mobile phone battery is different?

Every battery we see around us has only two terminals. Like: a 9v battery, an inverter battery, a T.V remote battery, or any other kind of battery. Then why in the world a mobile phone battery has more than two terminals?

We all know that out of 3 terminals, two terminals of a mobile phone battery must be positive and negative respectively. Now, if it’s a three-terminal battery then its third terminal can either be BSI or BTEMP(discussed below). And if it’s a four-terminal battery then the 3rd terminal is BSI and the fourth terminal is definitely BTEMP.

BSI pin

BSI stands for Battery System Indicator or Battery Status Indicator.

The work of this BSI pin is to give information such as the type and size of the battery to the mobile phone processor.

So when you plug in the mobile phone battery to your phone, this BSI pin automatically generates the signal that is received by the mobile processor.

This processor then determines the type and size or capacity of the battery which ultimately helps the processor to find out the voltage and current(mAh) of the battery.

Another important function of this BSI pin is this: Let’s say you suddenly remove the battery from the mobile phone. Due to this BSI pin immediately interrupts and tells the processor to shut down all communications. Thus preventing damage to our data or mobile phone.

BTEMP pin

BTEMP stands for battery temperature.

As the name suggests, it gives information to the processor regarding the battery’s temperature.

This BSI pin is connected to a thermistor which is internally connected to a temperature sensor to prevent the battery and mobile phone in case the battery overheats.

Now if you are not familiar with a thermistor or how it works, below are the two images demonstrating how it works. As the temperature around the thermistor changes so does its resistance.

So yes you can say it kind of works like an LDR but an LDR OR Light Dependent Resistor changes its resistance according to the intensity of light that falls on it. Whereas a thermistor changes its resistance according to the temperature of its surroundings.

Hence BTEMP terminal actually gives information about the amount of charge remaining in the battery to the processor.

And this way, the BTEMP pin helps the processor in controlling the status and charging current of the battery. Thus ensuring a longer battery life of mobile phones.

Conclusion

So with that being said, now whenever you will see a battery with 4 terminals you exactly know why it has more than two terminals:

For a 3-terminal battery: End terminals are positive and negative and the middle one is either BSI or BTEMP.

For a 4-terminal battery: End terminals are positive and negative and the middle ones are BSI and BTEMP.