Battery Management System in Solar Generator

Technology is an essential component to everyone’s lives, it has made transportation, access to food and services attainable. Along with its development is the progression of people’s creative minds, that’s why a lot of technological creations were produced. In this article we will mainly discuss the features and importance of the Battery Management System, especially for the batteries of the portable power station.

If you are someone who loves outdoor activities, or if you live in a place where power outage frequently happens, then having a portable power station is a good thing for you! Growatt, manufactures solar generators that are powered by LFP or NMC batteries. It has a large capacity with different ports that would provide you convenience while being off grid.

Battery Management System - Growatt solar generator

Battery Packs

Before we go in depth with the definition of the Battery Management System, let us first define what is a battery pack. A battery pack is basically a set of identical batteries or individual batteries that are connected, and has a protective cover or barrier called module. In each module, there are single cells that are connected in series and parallel. It is stated that the if the batteries are connected in parallel, they are most likely to produce a higher current and when in series, produces higher voltage.

Lithium-ion batteries

Lithium-ion (Li-ion) batteries are the most common type of battery used in portable devices. It is rechargeable and ensures uninterrupted power supply. This battery provides good features such as its low self-discharge characteristics and good performance when it comes to high-temperature. This is best used in electrical vehicles but can also be found in solar-powered generators. In terms of temperature, this battery has to be well-monitored. Mostly, the temperature ranges from -20 and 55 degrees Celsius. The functions of the battery can be negatively affected if it exceeded the mentioned temperature range. This phenomenon is also known as thermal runaway.

There are two types of batteries under the Li-ion, these are the LFP and NMC batteries. The LFP uses Lithium-phosphate as a cathode material (LiFePO4).  What is a cathode material? It is a component in batteries that determines its maximum capacity which includes materials like aluminum substrate. The materials in LFP are plenty but less expensive than the ones used in NMC. Also, the materials in this battery are known to be less harmful and are easier to recycle.

nmc bms vs lfp bms - Growatt

The NMC batteries are made up of combined nickel, manganese, and cobalt. NMC batteries are one of the most popular options for solar storage. It has a big capacity for storing energy, can last longer and requires a little effort to maintain.

LFPs are more efficient and can still operate even in the state of low charge. As mentioned above, the materials in LFP are less toxic, that is why it provides more assurance when it comes to safety. Furthermore, thermal runaway is also less likely to occur than in NMC. In terms of cost, NMC is less expensive, however, it is apparent that the LFP provides much more advantages, overall.

Battery Management System (BMS)

What should you know about Battery Management System?  

Batteries can be found from the smallest to the largest electronic device that you own. It provides life to your appliances that is why it is also important to know what’s in it. BMS is found in batteries that has various components and circuit-works. It is very common in rechargeable batteries but are also present in UPS (uninterruptable power supply) and cars. How a BMS is built and how it works may seem hard to understand but this article will provide you information that can be easily comprehended so you will know what battery to choose for your device.

BMS is identified as a technology that is constructed to ensure the good quality performance of a battery. It is essential as it said to be the brain of a battery pack. It serves a lot of functions that are very useful. The key role of the BMS is to ensure safety, regulate temperature, voltage, and the charge or discharge of current in the battery. It protects the overall function of a battery making it efficient and reliable to use.

Characteristics of a BMS

A Lithium-ion battery has an operating voltage that ranges from 2.5V to 4.2V. Performance beyond the stated limit would negatively affect the health of a battery and even reduce its capacity. BMS works to regulate the cell voltage safeguarding that any irregularities would not take place.

It is essential to assess the battery’s available capacity to ensure that it is continuously working on its best state. The BMS shows the battery’s percentage by measuring the available energy amount in it or the state of charge (SoC). On the other hand, the battery’s state of health is also monitored to measure its ability to store and produce energy.

A battery is composed of cells that work differently. Some may be lower or stronger than others. The BMS helps in equalizing the charge between each cells ensuring that it will perform the same with each other. It removes cells to prevent overcharging and allows the less charged to receive enough charging current.

BMS Safety features

Battery Management System’s function is not limited to monitoring the efficiency of a battery. It can also detect unsafe situations inside and even outside the battery pack. When such events occur, the BMS sends information making it evident to the user.

Additionally, a BMS can also provide cybersecurity. It is known that most devices have monitoring access through the internet. To prevent attacks in confidential data that may be stored in your device, it also good to note that the BMS has its own security features.

Different Types of Battery Management System 

Types of Battery Management System - Growatt

1. Centralized BMS Architecture – the entire battery pack is directly connected on just one BMS. The advantage of this type is it is very efficient because it only requires one BMS. However, it can also be disadvantageous since it must have a lot of ports so all the batteries can be connected. It will contain a lot of wirings and connections that may give you a hard time to maintain.

2. Modular BMS Topology – each battery pack is connected to a BMS that is divided into many replicated modules, there are interconnected control units (slaves). In this type, maintenance has been made easier and the wiring works is lesser. The only disadvantage of this one is it is a quite expensive.

3. Distributed BMS Architecture – in this type, each battery pack has its own BMS and are connected to the entire battery through a single channel. It is a construction that is simple, but costs higher than the others, and the maintenance are a bit difficult.

Important Features of BMS

  • Low Temperature Protection

Li-ion batteries have a thermal limit where it is unsafe to charge at a temperature below 0 degrees Celsius. Charging below its limit causes a chemical reaction called lithium plating – it is when the lithium ions move rapidly than the usual. BMS works by raising the temperature of the battery before it continues to charge, a BMS have embedded heating elements that automatically starts and stops when it senses unsafe occurrences. Having temperature sensors or thermistors are useful in the thermal management of your battery. Proper management of these sensors saves your battery from high or low temperature.

  • Overcurrent Protection

BMS has a sensing device that can monitor the flow of the current in a battery. When the maximum capacity has reached its limit, it releases loads that are beyond its norm. This process is done by the overcurrent protection that the BMS has.  If the BMS detects overcurrent flow, it triggers a switch that breaks the current path and once it has been stabilized, it automatically continues to charge. The OCP in BMS varies. It’s threshold can be adjusted depending on the need of your battery. It is suggested to consider the maximum and short-circuit current by setting the limit below their values to allow some clearance. It is also important to monitor the temperature of the battery because any false signals to the OCP causes the battery to stop unnecessarily. To avoid this, it is advised to be cautious in setting the OCP in BMS.

  • Short circuit protection

A short circuit happens when the current flows through an accidental path instead of following the right circuit, or simply the overcurrent flow in a battery. It causes the battery to overheat and may lead to fire. To avoid short circuits in your battery, the BMS provides short circuit protection which breaks the circuit in an instant as soon as an overcurrent is detected. This type of OCP is also called the thermal cutoff. Short circuit protection is somehow similar with how the overcurrent protection works as they both have something to do with excess current flow. Most OCP of Lithium batteries have a setting of around 200-300mA but if you are using a battery that has a large current flow, the OCP should also be increased.

Why is the Battery Management System important?

lithium battery bms - Growatt

The Battery Management System provides a lot of significance which includes the following:

  • The BMS ensures that your battery is performing properly without having any difficulties, and it allows you to manage errors that may occur.
  • Temperature monitoring is very important in batteries. Hence, BMS protects the battery from any damages that has something to do with temperature. It prevents damages like explosions caused by charging or over discharging beyond its thermal limit. It does not only provide protection to the batteries but also to the ones using it.
  • Without the BMS, the state of charge and state of health (which are indicators of the operating state of a battery) would not be assessed, making it difficult for the user to monitor the capacity and reliability of the battery.
  • Having a good, operating BMS does not only guarantee the safety and protection of the battery, but it also prolongs its lifespan that can reduce your maintenance and replacement costs. Indeed, having a BMS will not let your investment go to waste.

    To summarize, having a BMS provides an overall safety and protection feature to the battery and its user. Before choosing one for your application, you must see to it that the BMS is also considered because it plays a crucial role. With that, consumers should do research about batteries and how its BMS works as it also progresses along with technology. Batteries and Battery Management Systems vary depending on its usage and that is why manufacturing companies should also note that consumers want to have a reliable and efficient product. Make sure that the BMS you are going to choose augments protection from temperature, voltage, and others that were mentioned in this article.