13th June 2022

PCM vs. BMS: Which is Better?


How safe are your batteries? Safety systems are essential components of battery packs. They prolong the lives of the battery cells and protect users from mishaps like exploding batteries. Product designers often have to choose between using a PCM (Protection Circuit Module) and a BMS (Battery Management System).

But the question remains – which is better?

Introducing PCM

Protection Circuit Module (PCM) is a stand-alone protective circuit that is purely analogical. There’s no software connected to it, and it relies on predefined switch-off limits to protect batteries.

Batteries, especially lithium batteries, become dangerous when overcharged or deep discharged. A PCM protects the battery against very high charging voltages, very low discharging voltages, and high currents during discharging (short circuits).

Due to their limited capabilities, PCMs are affordable safety systems compared to BMS.

The Problems With PCMs

PCM is not as efficient as BMS because it can’t give the precise status of a battery pack. It won’t tell you the battery’s charging level, and it doesn’t always balance a battery’s state of charge properly. Sometimes, predefined switch limits are not accurate and it’s impossible to switch the battery pack on or off.

PCM also rarely measures battery cell temperature levels, which can lead to overheating. If left undetected, it can cause batteries to malfunction and devices to explode. This can also cause the deep discharge of batteries because they can’t conserve energy.

It’s also impossible to communicate with battery packs using PCM, which limits the device’s possibilities. You might be tempted to overcharge or undercharge without knowing the battery’s charging status. As a result, you couldn’t optimize the battery consumption, which would cause it to lose capacity quickly. This shortens your battery’s performance and lifetime.

Introducing BMS

Battery Management System (BMS) is like PCMs, but it offers more robust features for monitoring a battery’s health. It contains a microcontroller with integrated intelligent software that allows it to calculate and interpret different battery measurements like SOC (State of Charge) and SOH (State of Health).

It has a communication bus that can transfer information to the main application or other BMS. BMS can steer chargers or consuming units to utilize batteries entirely using the communication bus. This ability also allows BMS to protect batteries with larger capacities since it can intelligently adapt to their different needs.

BMS offers greater battery protection because it can detect abnormal events and alert users about them. At any time, you can perform a complete battery diagnosis to determine your battery pack’s health. In addition, you can keep a record of the battery life using BMS.

battery management system
ION Energy's Battery Management System


Here’s a quick comparison chart to better illustrate the features of PCM and BMS.



Stand-alone protective circuit

A complete management system that includes a control module, display module, wireless communication module, and collection module

Purely analogical with no integrated software

Contains a microcontroller with integrated intelligent software

Unable to get the battery’s precise charging status

Displays the battery’s SOC and SOH

Rarely surveys temperature levels, reducing the ability to protect the electronic device

Can detect normal and abnormal events, increasing its ability to protect the device

Unable to steer a charging unit or consuming unit

Has a communication bus that can drive chargers and consuming units, optimizing the capacity of batteries

Doesn’t keep a record of battery life

Keeps a record of battery life, including counting errors, counting usage, and storage time

Used for stand-alone battery packs

Can be used for interconnected battery packs since it can communicate with other BMS

Can cause a battery to overcharge or deeply discharge

Allows energy conservation

Low-cost solution

Relatively more expensive


Electric vehicles (EVs) run on rechargeable battery packs composed of multiple cell units that produce hundreds of volts of electricity. Almost everything that operates an electric car is dependent on these batteries. BMS helps protect these batteries from failing and ensures it’s highly optimized.

Battery packs can be highly unstable and must not be overcharged or deeply discharged. BMS keeps the battery running efficiently by monitoring the battery’s SOC and SOH. It ensures the battery operates within safety parameters and charging is controlled correctly. BMS provides EVs with an SOC indicator, similar to a fuel indicator in gas vehicles. This shows the driver the actual battery state, alerting him if the battery needs to be charged (SOC) or if the life cycle is near its end (SOH).

While PCM may work with batteries of simple electric devices such as electric shavers and power tools, BMS is the better safety device for electric devices like EVs that require complex and multiple battery packs.

About ION Energy

ION Energy is an advanced battery management and intelligence platform. We’re focused on building technologies that improve the life and performance of lithium-ion batteries that power electric vehicles and energy storage systems.

Our customers typically choose ION Energy because of its reliability, transparency, commitment to customer success, and innovative business models. OEMs and battery pack manufacturers across the globe choose ION’s integrated battery management solutions to continuously improve the life and performance of the battery.

Also read: Maxwell gets accredited with ISO 9001:2015 Certification

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