What is Stackable Battery and Why Do We Use Them?

Significant attention has been drawn to modular/stacking battery systems that enable several batteries to concurrently power multiple electrical gadgets. These batteries are a sophisticated energy technology that may be linked in parallel or series to improve capacity or voltage. They are commonly utilized for equipment that requires a high amount of voltage to function.

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What are Stackable Batteries? 

Stackable batteries are unique in the way that they may be readily joined or separated to meet the demands of a certain application. They are a relatively novel technology but are already widely used in a variety of industries such as electric cars, backup power grids, and portable energy systems.

These new portable power stations are customizable and more cost-effective to administer than fuel-driven and battery-driven generators with predetermined capabilities due to their modular architecture, which enables the users to add more batteries to enhance each unit's storage capacity and power output.

The Need for Stacking Batteries

For many years, petrol and diesel generators have been employed for a wide range of purposes, from powering machinery and tools on building sites to energizing the platforms of outdoor festivals. In , the combined global business and residential industry for portable generators (including devices with capacities of less than 5 kilowatts (kW), 5 to 10 kW, and 10 to 20 kW) was valued at $1.8 billion.

However, the acquisition pricing of these units might be deceiving, as they do not include ongoing expenses such as fuel, routine maintenance, and repairs. In addition, traditional fuel generators have limited capacity. Importantly, traditional generators were loud, polluting, and possibly dangerous to human health and the environment.

Before , when lithium-ion batteries were introduced, battery-powered portable power generators were not competitively viable. Although sealed lead acid (SLA) batteries, such as those found in the majority of cars, are less costly than lithium-ion batteries, SLA battery packs are not an appropriate technology for portable generators. They are nine times heavier and have a smaller carrying capacity. At the end of their lifespan (often 3 to 5 years), SLA batteries can no longer properly store a charge and must be replaced.

Hence, all these factors necessitate the need for novel technology.

Advantages of Stackable Batteries

Portable power stations that are stackable and scalable provide users with a greater degree of safety and independence. They are very adaptable and may be quickly tweaked to accommodate the special requirements of a given application. The efficiency of such batteries is unmatched and can offer steady and dependable electricity.

 Unlike fuel generators, stacking battery power stations allow customers to recharge their devices without transporting or storing dangerous substances. The freedom to run power plants in enclosed areas without disturbance and hazardous pollutants is another major advantage over its traditional counterparts.

Major Challenges

Despite the numerous benefits of stackable batteries, certain obstacles must be overcome. The expense of stacking batteries is a primary concern. While the price of batteries has decreased over time, stacking batteries are still more expensive than regular batteries.

Their susceptibility to humidity and other environmental conditions also affects their effectiveness and shortens their lifespan. In addition, they require comprehensive system administration to ensure safety and efficient functioning.

Design Phases of a Portable Stackable Battery(nl,cs,rm)

The stackable, modular, portable battery enables simple manipulation of the cells encapsulated in the battery pack. The battery has a Cell Module Controller (CMC) device, which also functions as a battery's thermal monitor. The CMC is responsible for the majority of battery pack functions.

Mechanical planning and module fabrication constitute the initial phase. It determines the active parts of the cell as well as its dimensions and shape. In the subsequent phase, the precise exterior parameters of the module are determined. Geometry defining is a crucial step in securing the various components of a battery pack. All elements, including the frame, heatsinks, thermal paste, and mechanical absorber, are tested and repaired. In the final step, module specifics and the Battery Management System are modeled.

Major Stackable Battery Products

Ultralife Corporation has introduced a lithium-iron phosphate (LiFePo4) energy storage device for use in robots, advanced robotics, military portable power systems, and vehicle-mounted APUs. The new battery, designated URB, has a container layout that permits more mobility throughout operations. The URB comprises a lifespan exceeding cycles, surpassing the lifetime cycle of existing stacked battery systems by around 200 cycles.

Joule Case has launched a new range of "clean and green" portable power stations in the 1- to 5-kW market category. Powered by stackable lithium-ion "energy blocks," these modular power stations produce emission-free, noiseless electricity whenever and wherever it is required.

BSL Battery has been a major contributor and manufacturer of High Voltage Storage Stackable LiFePo4 Batteries. Their novel 10-35 kWh BSLBATT HV Storage B-BOXHEV equipped with a distinct engineered system allows for simple connection, saving installers precious time. The stacking system offers versatile combinations ranging in voltage from 204.8V to 614.4V and capacity from 10.24kWh to 30.72kWh.

Another company, The Stack'd Series LFP batteries from Lithion are stackable and may be scaled from 9.6 kWh to 38.4 kWh in 4.8 kWh increments. Lithion's modular designs provide a "drop-in" replacement for lead acid batteries that is simple to adopt without the need for retooling. According to Lithion, this reduces procurement, stocking, and service expenses.

Research: Single-Cell and Stackable Battery Cells

An article published in Energy & Environmental Science focuses on the evaluation of the performance of a metal-free, stackable bipolar pouch battery using carbon black/ polyethylene composite film (CBPE) current collectors. Researchers examined both single and stacked bipolar pouch cells (stacked CBPE pouch) to compare their performance.

Using the ZnBr2/TBABr chemistry, a bipolar pouch composed of four cells stacked in series was created from the individual pouch cells. Even though the dimensioned, stacked system was more sophisticated than individual cells, specific energy remained unchanged and long-term cycling demonstrated minimal capacity degradation over cycles with 100 mAhg-1 capacity and an extra 500 cycles with 150 mAhg-1 capacity.

The stacked ZnBr2 system's steady cycling was important because it demonstrated that the battery cells in the bipolar stacked layout remained balanced, maintaining distinct cell voltage levels and outputs roughly matched and within safe values.

The researchers concluded that when thinner, sturdier, and more conductive carbon/polymer composite films are manufactured, battery cell performance might be improved readily. The results show a theoretically novel cell design that is widely applicable to numerous aqueous electrolyte compositions, as well as a specific high-performance instance.

Future Trends

Allied Market Research has published a report stating that the worldwide portable battery market was worth $10.8 billion in and is expected to grow to $27.5 billion by , at a CAGR of 10.4% from to . Stackable batteries are the core of the portable battery industry hence, their market is expected to rise exponentially.

The increasing trend of utilizing electric cars is one of the key drivers of this rise. To power the electric motor and give a range of more than 300 miles on a single charge, electric cars require efficient, high-performance batteries. Stackable batteries are an excellent choice for this purpose since they can be readily linked together to enhance the overall capability of the battery system.

The interest in alternative energy technologies, such as solar and wind power, is another important factor behind the development of stacking batteries. Renewable energy sources produce intermittent electricity, which may be stored using stackable batteries. Moreover, with the rising prevalence of smart grids and microgrids, it is anticipated that stacking batteries will play a significant role in the incorporation of sustainable energy sources into the grid. They can also provide backup power sources in the event of grid breakdown or power outages.

In short, the domain of stackable batteries is currently starting to dominate the energy storage market and its prospects are highly promising.

More from AZoM: How Can LiFSI Lithium Salts Reduce Battery Flammability?

References and Further Reading

Allied Marketing Research, . Portable Battery Market by Technology. [Online]
Available at: https://www.alliedmarketresearch.com/portable-battery-market
[Accessed 15 January ].

Evanko, B. et. al. (). Stackable bipolar pouch cells with corrosion-resistant current collectors enable high-power aqueous electrochemical energy storage. Energy & Environmental Science, 11(10), -. Available at: https://doi.org/10./c8eej

Baker, J., . The Future of Energy: Facing the "New Normal". [Online]
Available at: https://joulecase.com/the-future-of-energy-facing-the-new-normal/
[Accessed 16 January ].

Want more information on All In One Power System? Feel free to contact us.

Baker, J., . The Latest Generation Of Stackable Battery Power Stations Is Not Only Green But More Economical. [Online]
Available at: https://joulecase.com/the-latest-generation-of-stackable-battery-power-stations-is-not-only-green-but-more-economical-2/
[Accessed 15 January ].

BSL Batteries, . High Voltage Storage Stackable LiFePo4 Battery. [Online]
Available at: https://www.bsl-battery.com/hign-voltage-storage-stackable-battery-home-solar-system.html
[Accessed 17 January ].

Kennedy, R., . Stackable home battery with 9.6 kWh to 38.4 kWh of capacity. [Online]
Available at: https://www.pv-magazine.com//05/05/stackable-home-battery-with-9-6-kwh-to-38-4-kwh-of-capacity/
[Accessed 15 January ].

Large, . Modular Battery- Definition, Design And Usage. [Online]
Available at: https://www.large.net/news/8nu43pb.html
[Accessed 15 January ].

Lynn, A., . Stackable battery redefines portable power. [Online]
Available at: https://www.electronicspecifier.com/products/power/stackable-battery-redefines-portable-power
[Accessed 16 January ].

What is a Stackable Battery?
Are you looking into energy storage options and need a system that can grow with your needs? You might have come across the term "stackable battery" but aren’t entirely sure what it means or how it could benefit your solar setup or backup power plans.
These modular units are designed for flexibility and offer an efficient way to build up your energy reserves.

A stackable battery is essentially a modular energy storage unit, very often utilizing Lithium Iron Phosphate (LFP) chemistry for its safety and longevity. These individual battery modules are specifically designed to be physically stacked on top of each other and electrically interconnected. This clever design allows for the easy expansion of total energy storage capacity (measured in kilowatt-hours, kWh) or, in some configurations, an increase in system voltage, making them perfect for evolving solar energy systems, off-grid power, or emergency backup power needs.

Here at Gycx Solar, we frequently work with stackable battery systems, like the popular server rack style LFP batteries, because they offer our customers fantastic scalability and a clean, organized installation. If your energy needs increase down the line, a stackable system often allows for a simpler upgrade path.
Let’s dive into what "stackable" truly means and answer some common questions about this technology.

What is the meaning of stacked battery?

When you hear "stacked battery," are you picturing just any batteries piled up? Or is there something more to it? The term, especially in modern energy storage, refers to a much more sophisticated and engineered approach than simply heaping batteries together.

"Stacked battery" or "stackable battery" specifically refers to individual battery modules that are engineered to be physically placed one on top of another (or side-by-side in a dedicated rack) and then electrically interconnected to form a larger, unified battery bank. Each module is typically a self-contained unit with its own internal battery cells (often LFP), an integrated Battery Management System (BMS) for safety and monitoring, and designed connection points.

These modules can then be connected in series or, more commonly for increasing capacity at a set voltage, in parallel to achieve the desired overall system voltage and energy capacity.

Dive Deeper: More Than Just a Pile of Batteries

The concept of a "stackable battery" system is built on several key principles:

• Modularity: Each battery unit is a standardized module. This means you can start with a smaller capacity and add more identical modules later as your energy needs grow or your budget allows.
• Engineered Physical Design: These aren’t just random boxes. Stackable battery modules often have specific physical designs that allow them to interlock securely, or they are dimensioned to fit precisely into specialized racking systems (like 19-inch server racks). This ensures mechanical stability and a clean, organized installation.
• Purpose-Built Electrical Connections: The modules are designed with accessible terminals or integrated busbars that make it easy and safe to connect them together, either in series to increase voltage or in parallel to increase capacity (amp-hours) and current output.
• Integrated Battery Management System (BMS): This is crucial. Each modern stackable battery module typically includes its own sophisticated BMS. This BMS monitors the health of the cells within that module, protects against overcharge, over-discharge, over-current, and extreme temperatures, and performs cell balancing. In a stack, these BMS units may also communicate with each other or with a master BMS . /inverter to ensure the entire battery bank operates safely and efficiently.
• Applications: You’ll find stackable battery systems in various applications, most notably in residential and commercial solar energy storage, off-grid power systems, and as reliable backup power. The server rack batteries we often use at Gycx Solar are a perfect example of a stackable, modular design.

This engineered approach is a far cry from just placing loose battery cells on top of one another, which would be unsafe and impractical.

Does stacking batteries increase voltage?

If you’re looking to achieve a specific voltage for your system, you might be wondering if the physical act of stacking battery modules automatically leads to a higher voltage.
It’s a common question, and the answer depends entirely on how those modules are electrically wired together, not just how they are physically arranged.

Stacking battery modules can increase the total voltage if the modules are connected in series (where the positive terminal of one module is connected to the negative terminal of the next). However, if the modules are connected in parallel (all positive terminals connected together and all negative terminals connected together), the voltage remains the same as that of a single module, but the total capacity (amp-hours or Ah) and the current delivering capability of the bank increase.

Dive Deeper: Series vs. Parallel Connections Explained

Understanding series and parallel connections is fundamental to battery bank design:

• Series Connection (Increases Voltage):

  • How it works: You connect the positive (+) terminal of the first battery module to the negative (-) terminal of the second module. Then, the positive (+) of the second to the negative (-) of the third, and so on. The overall voltage of the battery bank is the sum of the individual module voltages.
  • Example: If you have three 12-volt modules connected in series, the total bank voltage becomes 12V + 12V + 12V = 36 volts.
  • Capacity (Ah) in Series: The amp-hour (Ah) capacity of the series string remains the same as the Ah capacity of a single module in the string.
  • Total Energy (kWh): Since kilowatt-hours (kWh) = Voltage (V) x Amp-hours (Ah) / , increasing the voltage while Ah stays the same does increase the total stored energy.
  • Use Case: This is done when you need to achieve a higher system voltage than what a single module provides (e.g., creating a 24V or 48V system from 12V modules, or even higher voltages for specialized industrial applications).

• Parallel Connection (Increases Capacity & Current Output):

  • How it works: You connect all the positive (+) terminals of the battery modules together, and all the negative (-) terminals together.
  • Example: If you have three 100Ah modules (each at 12 volts) connected in parallel, the total bank capacity becomes 100Ah + 100Ah + 100Ah = 300Ah.
  • Voltage in Parallel: The voltage of the parallel bank remains the same as the voltage of a single module (in this example, 12 volts).
  • Total Energy (kWh): Increases due to the increased Ah capacity at the same voltage.
  • Use Case: This is done when you want to increase your total energy storage (kWh) or your system’s ability to deliver higher current, while maintaining the system’s operating voltage. This is very common for modern 48V stackable LFP batteries used in solar; each module might be 48V (e.g., 51.2V nominal for LFP), and you parallel them to get more kWh.

Is it safe to stack batteries on top of each other?

Safety is always the number one concern when dealing with any type of battery, especially large energy storage systems. So, when you see these "stackable" designs, is it actually safe to place battery modules directly on top of each other? The answer is a conditional yes.

It is only safe to stack batteries that are specifically designed and engineered to be stackable. These purpose-built modules incorporate features for mechanical stability (like interlocking casings or designs for secure racking), ensure proper electrical isolation between units, and allow for adequate thermal management. Attempting to randomly stack batteries that are not designed for this purpose can be extremely dangerous, leading to risks of short circuits, physical instability and toppling, overheating, and potential fire hazards. Always, always follow the manufacturer’s guidelines and use appropriate racking or enclosures if specified.

Dive Deeper: Safety by Design in Stackable Systems

Manufacturers of reputable stackable battery systems put a lot of thought into safety:

• Mechanical Stability: Modules designed for stacking often have grooves, lips, or locking mechanisms that allow them to sit securely on one another. For larger stacks, or with server rack batteries, they are typically installed in robust metal racks or cabinets that are bolted down or secured to prevent tipping.
• Electrical Isolation and Connection: Terminals are usually designed to be protected to prevent accidental short circuits when modules are placed close together. Connection points (busbars or cables) are engineered for secure, low-resistance links between modules.
• Thermal Management: Batteries generate some heat during charging and discharging. Stackable designs must allow for adequate airflow around each module to dissipate this heat. Some enclosed rack systems may even incorporate fans for active cooling. Overheating is a major safety concern and drastically shortens battery life.
• Integrated BMS Protection: As discussed, each module in a modern stackable system typically has its own BMS. This provides a critical layer of safety by monitoring temperature, voltage, and current for each module, and can disconnect a module if unsafe conditions are detected.
• Weight Distribution: Manufacturers consider the weight of each module and the overall stability of a tall stack. There are usually limits on how high modules can be stacked without additional support or specific racking.
• Manufacturer Guidelines & Certifications: Always adhere strictly to the installation instructions provided by the battery manufacturer. Look for batteries that have relevant safety certifications (like UL for stationary batteries and UL for energy storage systems), as these undergo rigorous testing.

At Gycx Solar, safety is non-negotiable. We only use battery modules that are certified and explicitly designed for safe stacking and interconnection, and we ensure all installations comply with electrical codes and best practices.

How to stack batteries for higher voltage?

So you have a specific need for a higher voltage than a single battery module provides, and you have stackable modules designed for such configurations. What’s the correct way to connect them to achieve this voltage increase safely and effectively?

To "stack" (or more accurately, connect) batteries to achieve a higher total voltage, you must connect them in series. This involves connecting the positive (+) terminal of the first battery module to the negative (-) terminal of the second battery module.
Then, the positive terminal of the second module connects to the negative of the third, and so on, creating a chain. The overall voltage across the open positive terminal of the first module and the open negative terminal of the last module will be the sum of the individual module voltages.
It is absolutely crucial to use identical modules (same chemistry, capacity, age, and ideally, state of charge) when connecting in series.

Dive Deeper: The Ins and Outs of Series Connections

Connecting batteries in series requires careful attention to detail:

• Identical Modules are Key: When building a series string, all modules must be of the same type (e.g., all LFP), same nominal voltage, same amp-hour (Ah) capacity, same age, and ideally from the same manufacturing batch and at a similar initial state of charge. Mismatched cells or modules in a series string can lead to severe imbalances during charging and discharging. The weakest module can get over-discharged, while stronger ones might get overcharged, leading to damage and safety risks.
• BMS in Series Connections: This can be complex. If each individual module has its own BMS designed only for that module’s voltage, simply stringing them in series doesn’t mean the entire high-voltage string is optimally managed for overall cell balancing across all modules. For higher voltage series strings, a specialized master BMS that can monitor and manage the entire string, or individual BMS units capable of communicating and coordinating, might be necessary. Some stackable modules are designed with this in mind.
• Amp-Hour (Ah) Capacity: When batteries are connected in series, the total Ah capacity of the string is equal to the Ah capacity of the single lowest-capacity module in the string. It does not add up.
• Total Energy (kWh): The total stored energy (kWh) does increase because kWh = (Total Voltage) x (Ah Capacity of one module) / .
• Wiring and Fusing: Use appropriately sized wiring for the current and total voltage. Each series string should typically have its own fuse or circuit breaker rated for the string’s maximum safe current and voltage.
• Safety Precautions: Working with higher DC voltages is more dangerous than lower voltages. Always use insulated tools, follow proper safety procedures, and if you’re unsure, consult with a qualified professional.

While most of the stackable LFP battery systems Gycx Solar installs for residential and commercial solar (like 48V server rack batteries) involve paralleling modules to increase kWh capacity at a fixed voltage, we also have the expertise to design systems that require series connections for specific higher-voltage applications, always ensuring the configuration incorporates appropriate safety measures and battery management.

Stackable batteries represent a smart, flexible approach to energy storage, allowing systems to be tailored to specific needs and expanded over time. Understanding how they are designed for safe physical stacking and how series and parallel connections affect voltage and capacity is key to leveraging their benefits.

Whether you’re considering a new solar energy system with scalable storage, or looking to upgrade an existing one, Gycx Solar can help you navigate the options.

We specialize in designing and installing safe, efficient, and reliable energy solutions using quality stackable batteries. Reach out to us for an inquiry, and let’s build your energy future, module by module!