The Risks of Using a Single BMS for Parallel-Series LiFePO4 Battery Configurations

In the quest for higher capacity and longer-lasting battery packs, many enthusiasts and professionals alike consider connecting LiFePO4 cells in parallel-series configurations under a single Battery Management System (BMS). While the idea seems efficient at first glance, it harbors potential risks that could compromise the safety and longevity of your battery setup. In this detailed guide, we'll explore why using a single BMS for parallel-series configurations might not be the best approach for your LiFePO4 battery system.

Understanding Parallel-Series Configurations:

A parallel-series configuration aims to increase the total capacity and voltage of a battery pack by combining multiple cells. When cells are connected in parallel, their capacities add up, and when connected in series, the voltage increases. This method is enticing for those looking to amplify their battery system's overall power. However, the intricacies of managing such a setup with a single BMS present challenges often overlooked.

The Role of a BMS:

A Battery Management System is crucial for monitoring cell health, ensuring balanced charging and discharging, and protecting the battery from conditions like overcharging, deep discharging, and overheating. A well-functioning BMS is key to maximizing a battery's performance and lifespan.

The Complications of a Single BMS in Parallel-Series Setups:

  1. Uneven Charging and Discharging: In parallel-series configurations managed by one BMS, the system reads the collective voltage of parallel-connected cells, not the individual cell voltages. This setup fails to account for the slight variances in capacity and internal resistance inherent to each cell. As a result, some cells may overcharge or discharge faster than others, leading to imbalanced cell states and potential safety hazards.

  2. Increased Strain on Cells and BMS: Disparities in cell characteristics can cause uneven current distribution, with some cells working harder than others. Over time, this can strain both the cells and the BMS, reducing the overall efficiency and safety of the battery system.

  3. Safety Risks: The primary function of a BMS is to ensure each cell operates within safe parameters. A single BMS managing a parallel-series setup may miss critical voltage or temperature anomalies in individual cells, increasing the risk of battery failure or hazardous situations.

Why Multiple BMSs or Specialized Modules Are Recommended:

Employing a BMS for each series-connected group or utilizing specialized parallel modules offers a more reliable solution. This approach allows for precise monitoring and management of each cell's state, ensuring balanced charging and discharging, and significantly reducing safety risks. Products like the Daly parallel module have been designed specifically to manage the flow of current between cells in such configurations, offering an added layer of protection and efficiency.

While the allure of maximizing your battery pack's capacity and voltage with a single BMS might be tempting, the potential risks to safety and longevity are considerable. Opting for multiple BMSs or integrating specialized parallel modules can enhance your battery system's performance and durability. For those looking to delve deeper into optimizing their LiFePO4 battery setups, resources and products are available at LiFePO4 Oz:

LiFePO4 Oz is committed to providing the knowledge and tools you need to build safe, efficient, and long-lasting battery systems. Whether you're a DIY hobbyist or a professional, understanding the critical role of a BMS in your battery configuration is the first step towards achieving energy independence and reliability.

February 27, 2024 — Ernest Brindley

How to Top Balance Your LiFePO4 Cells? Is Top Balancing Necessary?

In the realm of DIY off-grid energy solutions, maximizing the performance and lifespan of your battery system is paramount. One method that frequently surfaces in discussions among enthusiasts is “Is Top Balancing LiFePO4 cells Necessary?” But what exactly does top balancing entail, and is it a crucial step for your setup?

Understanding Top Balancing LiFePO4 Cells

Top balancing is the process of ensuring all cells within a LiFePO4 battery pack are charged to the same voltage level of 3.65 volts per cell. This procedure aims to equalize the State of Charge (SOC) of each cell. By doing so means that each cell within a bank will have 100% SOC, even though the total capacity (ah) of each cell may vary.

Do You Need to Top Balance Your LiFePO4 Cells?

The necessity of top balancing hinges on several factors however most critical is if you’re running an Active Balancer. While top balancing can offer notable benefits, such as maximizing usable capacity and optimizing battery performance, however it being essential is deemed on:

  • Matched Internal Resistance (IR) & Capacity: Evaluate the uniformity of your LiFePO4 cells in terms of capacity and internal resistance. Top balancing becomes more critical when dealing with cells which have a higher variance between individual cells when considering their IR and Total Capacity.
  • Active Balancer: The job of an Active Balancer is to balance your cells as they cycle given their variance in IR and capacity. As a battery pack cycles, a variance in their IR and capacity WILL make the bank become unbalanced without using a balancer. As such, if you integrate an Active Balancer with your BMS, this will help balance your cells and therefore TOP balancing your cells becomes less critical, if at all critical.

How to Top Balance Your LiFePO4 Cells

For those opting to top balance their LiFePO4 cells, the following step-by-step approach can help achieve optimal results:

  1. Full Cell Charge: Utilize a balanced charger to charge all cells within the battery pack to their maximum voltage level of 3.65 volts per cell.
  2. Voltage Equalization: Monitor the voltage of each cell and adjust as necessary to ensure uniform voltage levels across the battery bank, maximizing usable capacity and minimizing stress on individual cells.
  3. Active Balancer Integration: Consider incorporating active balancers into your setup to automate the process of balancing cell voltages during charge and discharge cycles, reducing the need for manual intervention and enhancing system efficiency.

Optimizing Your LiFePO4 Battery System

While top balancing LiFePO4 cells can offer tangible benefits in terms of optimizing battery performance and longevity, its necessity varies depending on individual circumstances. By carefully assessing factors such as cell uniformity and BMS integration, DIY off-grid enthusiasts can make informed decisions regarding the implementation of top balancing in their battery setups. Whether you choose to top balance your LiFePO4 cells or not, prioritizing proper maintenance and monitoring is essential to maximize the efficiency and lifespan of your battery system. With these insights and methodologies at your disposal, you're equipped to navigate the intricacies of top balancing and optimize your LiFePO4 battery system for peak performance.


February 25, 2024 — Ernest Brindley
How Many Years Do LiFePO4 Batteries Last?

How Many Years Do LiFePO4 Batteries Last?

How Many Years Do LiFePO4 Batteries Last? Longevity Explored by LiFePO4 Oz

Battery lifespan is a crucial factor for consumers and industries alike. In the world of advanced battery solutions, LiFePO4 batteries stand out for their durability and longevity. At LiFePO4 Oz, we're often asked about the expected lifespan of these batteries, and we're here to shed light on what you can anticipate from your investment.

What Factors Influence the Lifespan of LiFePO4 Batteries? The lifespan of LiFePO4 batteries is influenced by several factors, including the number of charge-discharge cycles, depth of discharge (DoD), operating temperatures, and the quality of the battery management system (BMS). Proper usage and maintenance can significantly extend a battery's service life.

How Do Charge Cycles Affect LiFePO4 Battery Life? LiFePO4 batteries are renowned for their ability to handle a high number of charge cycles. On average, a quality LiFePO4 battery can endure between 2,000 to 5,000 cycles before reaching 80% of its original capacity, translating to years of reliable service.

What Is the Depth of Discharge and How Does It Relate to LiFePO4 Battery Longevity? Depth of discharge refers to the extent to which a battery is used before recharging. LiFePO4 batteries are less susceptible to capacity loss when regularly discharged to a shallow depth compared to deep discharges, which bodes well for their lifespan.

What Role Does Temperature Play in the Lifespan of LiFePO4 Batteries? LiFePO4 batteries are tolerant of a wide range of temperatures, but extreme conditions can shorten their lifespan. Optimal performance is typically maintained when operating between -20°C to 60°C.

How Does a BMS Contribute to the Longevity of LiFePO4 Batteries? A robust BMS protects LiFePO4 batteries from overcharging, deep discharging, and overheating. This smart technology is crucial in ensuring that the batteries operate within their ideal parameters, thereby maximizing their lifespan.

Can LiFePO4 Batteries Last Beyond Their Expected Charge Cycles? Many users report that LiFePO4 batteries continue to function beyond their expected charge cycles, albeit with reduced capacity. With proper care, it's not uncommon for these batteries to last upwards of 10 years.

The Enduring Power of LiFePO4 Batteries LiFePO4 batteries offer an impressive balance of performance, safety, and longevity. While the typical lifespan is around 5 to 10 years, many factors can extend or reduce this timeframe. By choosing LiFePO4 Battery Kits from LiFePO4 Oz, you're investing in a future-proof technology that promises to deliver long-term energy solutions.

November 13, 2023 — Ernest Brindley
Is it Bad to Completely Drain a LiFePO4 Battery?

Is it Bad to Completely Drain a LiFePO4 Battery?

Is it Bad to Completely Drain a LiFePO4 Battery? Insights from LiFePO4 Oz

Introduction: LiFePO4 batteries have revolutionized the way we store and use energy, particularly in renewable systems and electric vehicles. However, one question that often arises is the impact of fully depleting a LiFePO4 battery. At LiFePO4 Oz, we believe in not only providing high-quality battery solutions but also in educating our customers about the best practices for battery maintenance.

How Does Deep Discharging Affect LiFePO4 Battery Health? Unlike traditional lead-acid batteries, LiFePO4 batteries are designed to handle deep discharge scenarios without significant damage. However, consistently depleting any battery to its lowest capacity can hasten the wear and tear of its components, potentially leading to reduced longevity.

Why Should You Avoid Completely Draining LiFePO4 Batteries? Allowing a LiFePO4 battery to discharge completely can be detrimental to its internal structure, potentially impairing its capacity to hold a charge effectively. In severe cases, this deep discharge might cause irreversible damage, rendering the battery inoperable. The inherent stability of LiFePO4 chemistry does provide some resilience, but to maintain optimal performance and longevity, it is advisable to avoid situations where the battery is fully exhausted.

What Are the Best Practices for LiFePO4 Battery Discharge? To maximize the lifespan and efficiency of your LiFePO4 battery, it's recommended to maintain the charge between 20% and 80% of the battery's capacity. This practice, known as shallow cycling, can significantly extend the number of charge cycles your battery can achieve.

How Does the Battery Management System (BMS) Help? The BMS in LiFePO4 batteries plays a crucial role in preventing complete discharge. It monitors cell voltages and can disconnect the battery from the load before it gets too low, preserving the health of the cells.

Can You Recover a Fully Drained LiFePO4 Battery? If a LiFePO4 battery is fully drained, in many cases, it can be recovered with a proper charger. However, the recovery process can be more challenging if the voltage has dropped below a certain threshold, requiring specialized charging procedures.

What Are the Long-Term Impacts of Regularly Draining LiFePO4 Batteries? Regularly draining a LiFePO4 battery to empty can lead to a gradual decrease in its capacity over time. It's essential to follow the manufacturer's guidelines to ensure that your battery maintains its performance in the long run.

Conclusion: The Importance of Proper Charging Habits for LiFePO4 Batteries While LiFePO4 batteries are robust and can handle deep discharges better than other battery types, it is still best practice to avoid completely depleting them. Proper charge management not only preserves the battery's life but also ensures consistent performance. At LiFePO4 Oz, our LiFePO4 Battery Kits come with advanced BMS technology to help manage these concerns, providing you with a reliable and durable energy storage solution.

November 13, 2023 — Ernest Brindley
Is LiFePO4 Better Than Lithium?

Is LiFePO4 Better Than Lithium?

Is LiFePO4 Better Than Lithium?

An Expert Analysis by LiFePO4 Oz

Introduction: The evolution of battery technology has been pivotal in shaping the energy solutions of tomorrow. At the forefront of this revolution is the lithium iron phosphate (LiFePO4) battery, a variant of lithium-ion that stands out for its unique properties. As specialists at LiFePO4 Oz, we delve into the aspects that may make LiFePO4 a superior choice for certain applications.

What Sets the Chemistry of LiFePO4 Apart from Standard Lithium-Ion Batteries? LiFePO4 batteries utilize lithium iron phosphate as the cathode material, coupled with a graphite carbon anode. This distinctive chemistry endows LiFePO4 batteries with remarkable stability and safety profiles compared to traditional lithium-ion batteries that use various lithium metal oxides as cathodes.

Why Are LiFePO4 Batteries Considered Safer Than Traditional Lithium Batteries? Safety is a significant advantage of LiFePO4 batteries. The strong chemical bonds within the LiFePO4 cathode material greatly reduce the risk of thermal runaway and overheating – common concerns associated with lithium-ion batteries.

How Does the Energy Density of LiFePO4 Compare to Other Lithium Batteries? While LiFePO4 batteries may have a lower energy density than some lithium-ion variants, they maintain a balance between efficiency, cost, and safety. This makes them suitable for electric vehicles (EVs) and stationary applications where safety and cycle life are prioritized over energy density.

Is the Cost of LiFePO4 Batteries Competitive with Traditional Lithium Batteries? Initially, LiFePO4 batteries might seem more expensive; however, their longevity and the absence of expensive metals like nickel and cobalt can lead to a lower total cost of ownership, especially when factoring in the extended cycle life and durability.

What Are the Cycle Life Expectations for LiFePO4 vs. Traditional Lithium Batteries? LiFePO4 batteries often exceed 3,000 charge cycles and can even surpass 10,000 under optimal conditions, significantly outperforming traditional lithium-ion batteries in lifespan.

How Do Environmental and Resource Considerations Affect the Choice Between LiFePO4 and Lithium Batteries? LiFePO4 batteries contain no nickel or cobalt, making them a more environmentally conscious choice. The abundance of iron and phosphate minimizes the ecological and social impact associated with the mining of other battery materials.

What Temperature Ranges Can LiFePO4 Batteries Operate In Compared to Lithium Batteries? LiFePO4 batteries have a broad operating temperature range, making them robust in various environmental conditions, which can be particularly beneficial for applications in extreme climates.

How Does the Lower Voltage of LiFePO4 Batteries Impact Their Use? The typically lower voltage of LiFePO4 cells may require adjustments in battery pack design but also allows for compatibility with devices designed for lower voltage ranges, offering versatility across applications.

Why Might LiFePO4 Batteries Be the Preferred Choice for the Future?

The growing market share of LiFePO4 batteries in the EV sector, led by giants like Tesla and BYD, signifies a shift towards more sustainable and safe battery technologies. With LiFePO4's advantages in safety, cycle life, and environmental impact, it is poised to play a crucial role in the future of energy storage solutions.

LiFePO4 Oz is committed to advancing this promising technology, offering an array of LiFePO4 Battery Kits that epitomize the balance between performance, safety, and environmental responsibility.

November 13, 2023 — Ernest Brindley
What is the Difference Between a BMS and a Balancer?

What is the Difference Between a BMS and a Balancer?

What is the Difference Between a BMS and a Balancer?

When utilizing lithium batteries in any application, the terms 'Battery Management System' (BMS) and 'balancer' often surface. Though they are both critical for battery health and efficiency, they fulfill different roles within the battery's ecosystem. Understanding these differences is essential for anyone engaged in the DIY off-grid energy space.

The Role of a Battery Management System (BMS)

A BMS is an electronic system incorporated within lithium battery packs. It's responsible for protecting lithium cells against a multitude of risks that can reduce the battery's lifespan or lead to unsafe conditions. These risks include overcharging, deep discharging, operating under high or low temperatures, and handling excessive current. If any of these parameters are exceeded, the BMS intervenes by disconnecting the flow of current to or from the battery bank, effectively mitigating potential damage.

The Function of a Balancer

On the other hand, a balancer is designed to ensure uniformity among the cells in a battery pack. Over time, individual cells within a lithium battery can develop variations in charge levels, which can affect performance and longevity. A balancer corrects these imbalances by evening out the state of charge across all cells.

Types of Balancers: Passive vs. Active

Balancers are categorized into passive and active systems:

  • Passive Balancers: These systems level the charge by dissipating the excess energy from more charged cells as heat. This process is simpler and less costly but is not energy-efficient since the excess charge is not reused but lost.

  • Active Balancers: In contrast, active balancers redistribute energy from cells with a higher charge to those with a lower charge. This method not only maintains balance but also conserves energy within the battery system, enhancing overall efficiency.

Both a BMS and a balancer are integral to the health and functionality of lithium battery packs. A BMS protects against unsafe operating conditions, while a balancer ensures all cells work cohesively, maintaining balance and extending the battery's service life. For individuals invested in creating sustainable energy solutions, comprehending the distinct functions of these systems is invaluable.

For a deeper exploration into the specific types of balancers and their benefits, visit our detailed articles: What is a Passive Balancer? and What is an Active Balancer Module?.

November 13, 2023 — Ernest Brindley

What is the lifespan of a LiFePO4 battery?

What is the Lifespan of a LiFePO4 Battery?

Understanding the Longevity of LiFePO4 Batteries

Table of Contents

  1. Introduction to LiFePO4 Batteries
  2. Lifespan: How Long Can You Expect a LiFePO4 Battery to Last?
  3. Key Variables Impacting the Durability of LiFePO4 Batteries
  4. Best Practices for Extending Your LiFePO4 Battery Life
  5. Frequently Asked Questions

LiFePO4 batteries have gained a reputation for their impressive cycle life and reliability. When it comes to choosing a resilient battery, LiFePO4 frequently stands out for its extended lifespan, lighter mass, and superior safety attributes.

So, what is the actual lifespan of a LiFePO4 battery? And how do you make it last as long as possible? In this guide, we will break down these questions and more.

Introduction to LiFePO4 Batteries

LiFePO4 stands for Lithium Iron Phosphate, a type of lithium-ion battery that has become increasingly popular for uses beyond just golf carts and marine applications. Its application has expanded to consumer electronics, with some gadgets containing as many as 16 LiFePO4 cells.

Lifespan: How Long Can You Expect a LiFePO4 Battery to Last?

A well-maintained LiFePO4 battery can have a lifespan ranging from 5 to 10 years. The longevity of these batteries is closely tied to how well they are looked after.

Number of Charge Cycles for LiFePO4 Batteries

LiFePO4 batteries are known for their robust 3,000 to 5,000 charge cycles, considering an 80% depth of charge. This significantly outperforms traditional lead-acid batteries, which usually last for about 650 charge cycles.

Key Variables Impacting the Durability of LiFePO4 Batteries

Various factors can either extend or reduce the lifespan of your LiFePO4 battery, such as how you store it, maintain it, and the frequency with which you charge it.

Here are some effective tips to ensure you get the most out of your battery:

  • Avoid Overcharging: Overcharging can generate excessive heat and risk a fire. LiFePO4 batteries should only be charged up to 3.5v per cell to maintain a safe temperature.

  • Proper Storage: To maximize battery life, LiFePO4 batteries should be stored in a cool environment, ideally between -20°C and 25°C.

  • Avoid Over Discharging: The recommended depth of discharge (DoD) for LiFePO4 batteries is 70%. Over discharging can cause irreparable damage to the cells.

Best Practices for Extending Your LiFePO4 Battery Life

  1. Use Compatible Chargers: Ensure you are using the charger designed for your specific battery type.

  2. Minimize High-Power Applications: Certain apps and functions can quickly drain your battery. Reducing their use can extend battery life.

  3. Regular Terminal Check: Periodically examine the terminal bolts for any sign of loosening or oxidation and clean them as needed.

Frequently Asked Questions

In summary, while LiFePO4 batteries may have a higher upfront cost, their extended lifespan and superior performance attributes make them a worthwhile investment. If you are diligent about its storage and charging conditions, a LiFePO4 battery can offer reliable, long-term service, outperforming traditional lead-acid batteries in most aspects.

Remember, the key to longevity is proper maintenance and understanding of how to best care for your LiFePO4 battery.

September 15, 2023 — Ernest Brindley

What is the best LiFePO4 battery cell?

What is the Best LiFePO4 Battery Cell for DIY Battery Packs? [2023 Edition]

Choosing the perfect LiFePO4 battery cell for your DIY battery pack can be challenging, especially with the multitude of options available. In this comprehensive guide, we break down top LiFePO4 battery cell manufacturers, compare the best models, and help you decide which LiFePO4 battery cell will suit your DIY project best.

Table of Contents

  1. Introduction to LiFePO4 Batteries
  2. Top LiFePO4 Battery Cell Manufacturers
  3. Comparative Analysis of Popular Brands
  4. Best Choice for DIY Battery Packs
  5. Most Cost-Effective Options
  6. Final Thoughts

Introduction to LiFePO4 Batteries

LiFePO4 (Lithium Iron Phosphate) batteries offer superior safety features, long lifespans, and are eco-friendly. They are an ideal choice for DIY battery packs for various applications, including solar energy systems, backup power solutions, and electric vehicles.

Top LiFePO4 Battery Cell Manufacturers


  • Key Models: 280Ah, 302Ah
  • Applications: Electric vehicles, Energy Storage


  • Key Models: 230Ah, 280Ah, 304Ah
  • Applications: Commercial vehicles, Solar energy storage


  • Key Models: Various
  • Applications: EV, Energy Storage


  • Key Models: 272Ah
  • Applications: General Purpose


  • Key Models: 220Ah, 280Ah
  • Applications: EV

Comparative Analysis of Popular Brands

Brand Impact

  • CATL: ★★★★★
  • EVE: ★★★★
  • Lishen: ★★★★
  • REPT: ★★★★
  • CALB: ★★★★

Product Line

  • CATL: ★★★★
  • EVE: ★★★★★
  • Lishen: ★★★
  • REPT: ★★★
  • CALB: ★★★


  • CATL: ★★★★
  • EVE: ★★★★
  • Lishen: ★★★★★
  • REPT: ★★★★★
  • CALB: ★★★★★


  • CATL: ★★★★
  • EVE: ★★★★★
  • Lishen: ★★★★
  • REPT: ★★★
  • CALB: ★★★

Best Choice for DIY Battery Packs

Considering the availability, brand impact, and product line, EVE's LF280K emerges as the top choice for DIY battery packs. Its deep cycle life of up to 6,000 cycles makes it a reliable and long-lasting option.

Most Cost-Effective Options

As of late 2021 and early 2022, the LF230 from EVE holds the title for the most cost-effective LiFePO4 battery cell, mainly due to supply shortages affecting the prices of other models. It is a strong contender for those seeking a balance between cost and performance.

Final Thoughts

When it comes to selecting the best LiFePO4 battery cell for DIY battery packs, EVE stands out in terms of product variety and availability. Among its models, the LF280K offers the best performance, making it the ideal choice for those who prioritize reliability and lifespan. However, if cost is a significant factor, the LF230 is a valuable alternative.

With this comprehensive guide, you are now equipped to make an informed decision for your next DIY project involving LiFePO4 battery cells.

September 04, 2023 — Ernest Brindley

Demystifying LiFePO4 Battery Grades: Auto Grade vs. Solar Grade

Confused about inconsistent LiFePO4 battery cell grading? Wondering if Auto Grade or Solar Grade cells are right for you? We're here to cut through the confusion by ditching 'Grade A, B, or C' labels that vary by manufacturer. Our article offers insights into the benefits of our rigorously tested Auto Grade and Solar Grade cells, each designed for specific applications. Learn why our revamped system is the key to simplifying your choices and ensuring you get the right cell for your project.
September 04, 2023 — Ernest Brindley

What is an Active Balancer Module?


What is an Active Balancer Module?

An Active Balancer Module (Active Balancer) is a unit which will “Actively” balance the voltage between 2 or more cells connected in series.  When charging/discharging cells connected in series, each cell will behave differently depending on their internal resistance which will result in the being unbalanced.  The more you charge/discharge the battery bank, the State of Charge (SOC) and voltage variance between the cells will increase, resulting in 1 cell having a greater SOC, while another cell within the same bank having a lower SOC.  The problem with this is the potential for the cell with the higher SOC being overcharged, while the cell with the lower SOC being over discharged and therefore those cells experiencing a greater derogation in comparison to the other cells.

An Active Balancer will monitor and transfer current between cells within a bank.  Cells with a higher SOC, to cells with a lower SOC ensuring they are better balanced and drastically reducing the chance of one particular cell in the bank being over charged/discharged.

Unlike a passive balancer, an active balancer will operate while a battery bank is being charged, discharged or even left in storage.

October 21, 2022 — Ernest Brindley

What is a Passive Balancer?

What is a Passive Balancer?

Most BMS’s will have a built-in balancing function, however for the majority of BMS’s currently available this will be a Passive Balancer.  A Passive Balancer will attempt to balance cells within a bank by increasing the resistance to cells with a higher voltage/State of Charge (SOC), allowing for more current to flow to cells with a lower voltage/SOC.  A Passive Balancer only works while the bank is being charged, which means cells within a bank can still fall out of balance while being discharged.
October 21, 2022 — Ernest Brindley

What is a BMS Parallel Module?


What is a BMS Parallel Module?

The main purpose of a BMS Parallel Module is to regulate the current flow between 2 or more banks of batteries connected in parallel.

When 2 or more banks of batteries are connected in parallel, the State of Charge (SOC) of the different banks will equalise.  That means, they will transfer current from the highest charged bank to the lowest charged bank until they have the same SOC, and therefore have the same voltage.  With LiFePO4 Cells, this transfer of energy can be significant, and the high current flow will most likely be too great for BMS, while also causing damage the LiFePO4 cells.

The charge profile for LiFePO4 cells is relatively flat, that means there can be a large variance in the SOC between 2 or more cells, with a small variance in their comparative voltages.  For example, you may have only 0.1V difference in voltage between 2 cells, however there will be a big variance in the SOC between these cells.

LiFePO4 Charge Profiles

By using a parallel module, if 2 or more banks are connected in parallel, it will restrict the amount of current transferred between the banks, therefore protecting the BMS and the cells from any potential damage.

Some might say that if you have 2 more bank always connected in parallel then they will always be equalised… Although this might be true in principle, practically there are a couple of scenarios which may see 2 banks attempt to equalise, creating a situation of high current transfer, such as:

  1. Before initially connecting banks in parallel, you should need to top balance ALL cells which will ensure they have the same SOC otherwise they will equalise when connected in parallel.
  2. If you have 2 banks connected in parallel, 1 bank maybe disconnected by the BMS due to one of the protection parameters (like cell voltage variance) being triggered. If this happens, then one bank will continue to provide/receive current and therefore increasing the variance of the SOC between the banks.  When you attempt to reconnect the bank into the parallel circuit, the banks will attempt to rebalance transferring unrestricted current.
By using a Parallel Module with the BMS for each bank, it will govern the amount of current able to be transferred between cells and avoid any potential damage to the BMS/s or cells.
October 21, 2022 — Ernest Brindley