Technologies are becoming lightweight and smaller to allow for portability. From drones, laptops, and phones to power tools and medical devices, these applications require a high amount of power to function and a battery that guarantees long run times and safety.
Companies have turned to lithium-ion battery packs to provide the desired solutions for mobile applications. When selecting battery packs for portability, there are some unique design considerations when choosing this type of battery chemistry for these devices.
Battery Pack Dimension and Weight Limitations
Typically, when it comes to battery packs, a larger battery provides higher amounts of current for longer lengths of time. In the case of portable devices, there are weight and space limitations that force manufacturers to design packs that still provide high amounts of power while still being light enough to carry. Lithium-ion batteries come in several cell formats to accommodate portable devices. These formats include cylindrical cells, prismatic cells, and pouch polymer cells.
Custom battery packs that are manufactured for a portable device.
Cylindrical Cells
Cylindrical cells are shaped like common alkaline batteries found in electronics. They come in standard sizes of 18mm diameter with 65mm length (18650 types), 26mm diameter with 65mm length (26650 types), and 21mm diameter with 70mm length (21700 types). While offering high energy and power, these devices cannot accommodate portable devices that require thinner battery format profiles. Cylindrical cells are commonly found in portable medical instruments, handheld commercial and military devices, and power tools.
Prismatic Cells
Prismatic cells offer a design option for portable devices that have thinner dimension limitations and cannot use cylindrical cells. They have steel or aluminum casing, often referred to as a "can", with a standard size of 34mm diameter with 50mm length and 10mm thickness. Offering robust mechanical proficiency, these cells are often found in laptops, tablets, phones, and portable medical monitors.
Polymer Cells
Polymer cells, also called pouch cells, are designed like a foil pouch to offer very thin and lightweight profiles. There are no standard sizes for this type of battery pack, as they are a unique option for portable devices where the battery pack may have to curve or come in a customized shape due to the space limitations inside the device. Polymer pouch cells offer high energy density and are often found in portable applications such as wearable devices, medical equipment, drones, thin laptops, and tablets.
Many manufacturers offer customization options for these cell profiles. Yet keep in mind that they may also have set standards on how lightweight and small the lithium-ion battery can become without compromising on safety.
Watt Hour Limitations
Watt hours signify the amount of energy that a device will use during a specific measure of time. So, one watt of power per one-hour period. National and international transportation regulations limit the number of watt-hours for lithium batteries in portable devices to a maximum of 100 watt-hours (Wh) or less for laptops, cameras, phones, and other applications that will be shipped.
When calculating watt hours, you need to understand the amount of voltage and capacity of the lithium-ion battery. For a pack that has a voltage of 12v and an amp hour of 100 Ah, you would multiply 12v by 100Ah to determine the watt-hours, which would be 1,200Wh.
Charging Design Options
When it comes to charging lithium-ion batteries, there are different charging parameters to consider. First, lithium-ion batteries cannot be charged using the same battery charger as other battery chemistries. Each manufacturer will have specific ways of designing lithium-ion batteries, which will result in slight differences in both current and voltage settings. Lithium-ion cell chemistries also have a lower resistance due to the materials used in creating it, which often results in a faster charging speed.
Due to these differences, chargers need to be designed with special parameters to ensure the proper charging current without overcharging or undercharging the battery cells in the pack. It is ideal to design a custom charger for the specific battery pack versus using an off-the-shelf (commercial) model.
BMS Designs
Battery management systems (BMS) are control devices designed to protect the battery from common issues associated with lithium-ion batteries, such as high temperatures, overcharging, undercharging, and thermal runaway. National and international transportation regulations require that all types of lithium-based batteries have a BMS installed regardless of whether the device is portable.
For portable devices, the BMS components will have similar features such as temperature monitoring, overcharging monitoring, over-discharging management, and fault diagnosis. These protection systems will also come with additional requirements such as interoperability and integrated circuit (IC) improvements. Interoperability functions allow the BMS to communicate important battery condition information over networks and controller systems, which is an important design feature for portable devices.
Enclosure Special Features
Safety is a key factor to consider for portable devices using lithium-ion batteries. If the device becomes dropped or mishandled, the battery pack needs to be protected from punctures and other forms of damage. Circuit protection such as polymeric positive temperature coefficient (PPTC) devices in the form of a strap or disc device can be placed on prismatic and cylindrical lithium-ion cells to protect circuits during shipping and transportation.
Enclosures can also be designed to further protect lithium-ion batteries from shocks and vibrations while also being designed to allow for venting gases and heat dissipation. Manufacturers offer a range of enclosure options that include shrink wrap, vacuumed form plastic, and injection molded plastic. These enclosures can go through safety drop testing to ensure durability and reliability for lithium-ion batteries in portable devices.
Portability Regulations
Many transportation regulations are standard for all lithium-ion batteries whether they will be used in portable or non-portable devices. All lithium batteries must come with BMS components whether shipped separately from devices or installed within devices. Lithium batteries also must have 100 watt-hours or less for transportation unless receiving approval from the transportation carrier. Safety testing and certification also apply to lithium-ion portable devices.
New standards and regulations are also rolling out for lithium-ion batteries. Starting in January 2026, new mandatory shipping rules require that lithium-ion batteries have a state of charge (SoC) of 30 percent or less when shipped alone. There is also a new requirement for non-specification packaging used when shipping lithium-ion batteries contained within devices or packed with devices. This requirement requires the packaging to meet the 3.0 meter-stack test.
Summary
Portability design options for lithium-ion battery packs will vary depending on the device, industry requirements – such as for medical and military devices, and national/international regulations.
A custom battery pack manufacturer like Epec can help you determine the types of technologies and features necessary to include with your lithium-ion battery pack to ensure functionality and reliability while maintaining safety.
Key Takeaways
- Lithium-ion battery packs are the preferred choice for portable devices due to their high energy density, lightweight design, and ability to be customized for different applications, including laptops, drones, and medical devices.
- Battery pack dimensions and weight are critical considerations, with cylindrical, prismatic, and polymer pouch cells offering different advantages depending on space constraints and power requirements.
- Battery management systems are mandatory for lithium-ion battery packs, ensuring protection against overcharging, overheating, and thermal runaway while also enabling communication and interoperability for advanced device monitoring.
- Regulatory compliance is essential, as lithium-ion batteries must meet international watt-hour limits, safety testing, and upcoming 2026 shipping regulations, including a 30% state-of-charge limit for standalone shipments.
- Custom enclosure designs enhance durability and safety by protecting against shocks, punctures, and overheating, with options such as shrink wrap, vacuum-formed plastic, and injection-molded casings ensuring reliability in portable applications.
