How to Choose a Mobile Power Bank: 5 Key Points to Evaluate Capacity, Output, and Safety

When your smartphone’s battery runs low while you’re on the go, a portable charger (power bank) is a reliable companion. However, if you choose one based solely on capacity or maximum output numbers, you might end up with something that is difficult to carry around or does not support the fast charging you need.

When making a selection, the basic approach is to decide on the devices you will use and the duration of your outing, then check five key aspects: capacity/output, standards, ports, size/weight, and safety. By also looking at the input for charging the unit itself and the output distribution when multiple devices are connected, you can narrow down the conditions that best fit your usage style.

This article explains everything step by step, from how to read units of measurement to checking procedures before purchase. It also covers a detailed timeline of fast charging, Qi2, bringing batteries on airplanes, and the disposal of used units. Rather than a ranking of specific products, this is a guide designed to help you identify the exact specifications you need.

What is a Portable Charger: Determining Requirements Based on Usage Scenarios

This image illustrates scenarios where a portable charger is used during commuting, outings, and travel. We will organize your requirements based on time spent away from home, the devices you use, the number of top-ups needed, and how you carry it.

A portable charger is a portable power source featuring a built-in rechargeable battery that can be used repeatedly. It utilizes the energy stored within the unit to supply power to smartphones and tablets via USB terminals and other ports. Unlike standard AC chargers that require a wall outlet, you can use it on the go as long as you charge the unit beforehand. Consumer Affairs Agency: “How Portable Chargers Work” (in Japanese)

If you want to charge laptops or multiple devices, check the unit’s output standards and number of ports against the power required by your devices. Even if terminals like USB-C are identical, the supported power delivery and functions are not necessarily the same. USB-IF Power Delivery and Power Management Overview

First, try writing down the following items:

• Devices to charge: Just a smartphone, or do you also use earphones, tablets, and laptops?
• Time away from home and required charge amount: A quick top-up during a short outing, a full day’s worth of power, or multiple days without access to an outlet?
• Simultaneous connections: Charging one device at a time, or connecting multiple devices simultaneously?
• How it is carried: Stored in a pocket, commuter bag, or travel bag?
• Travel and emergency preparedness conditions: Will you be using an airplane, or storing and inspecting it at home?

For example, if your goal is simply to top up your smartphone until you return home, you can decide based on the required amount of charge and portability. If you use a laptop on the go, check not only the capacity, but also the voltage and wattage that your specific laptop can accept beforehand. For applications requiring AC outlets for home appliances, consider your needs—including portable power stations—based on the input requirements of the devices you plan to use.

Capacity, Power, and Charging Units to Know Before Choosing

Specification tables are filled with mAh, Wh, W, V, and A. Separating the numbers used to compare capacity from the numbers related to power transferred during charging makes it much easier to determine what you should choose.

What is the Difference Between mAh and Wh? How to Read Capacity and Number of Charges

This diagram assumes a 10,000mAh, 3.7V power bank and a 5,000mAh, 3.85V device, compared in Wh. This is a calculation example before subtracting losses or consumption from device usage, and does not indicate the actual number of charges.

mAh (milliamphours) represents electric charge capacity, while Wh (watt-hours) represents energy. Because voltage conditions cannot be determined by mAh alone, values are converted to Wh to compare the energy stored in different batteries. Conversion using nominal voltage is calculated with the following formula: NIST Unit Conversion, MLIT Wh Conversion Guide

Wh ＝ mAh × Nominal Voltage (V) ÷ 1,000

For example, assuming a portable charger with 10,000mAh and 3.7V, and a device battery with 5,000mAh and 3.85V, the calculation is as follows:

Calculation Item	Assumed Conditions	Energy
Portable Charger	10,000mAh × 3.7V ÷ 1,000	37Wh
Device Battery	5,000mAh × 3.85V ÷ 1,000	19.25Wh
Ratio Before Including Losses	37Wh ÷ 19.25Wh	Approx. 1.92 charges

This is a calculation example before subtracting energy lost during conversion and charging. In reality, losses occur during output from the device and within the device’s charging circuitry, and using the device while charging also consumes energy. Furthermore, the number of charges varies depending on the remaining battery levels of both the power bank and the device at the start of charging, as well as the target charge percentage. Therefore, please do not use this example as the exact number of charges for a specific product. Technical Explanation on Voltage Conversion Efficiency

Another important point is to distinguish between battery cell capacity and the rated output capacity that can be drawn from the USB port. The 10,000mAh indicated in the product name, the internal battery voltage and capacity, and the rated capacity at 5V output are not necessarily figures based on the exact same conditions.

As a specific example, while the MOT-MBSS10002 has a product capacity of 10,000mAh, its user manual lists an internal battery of 7.7V, 5,000mAh, and 38.5Wh, along with a rated output capacity of 5V and 6,600mAh. Do not simply look at the numbers and conclude that it is “only half,” but rather check which voltage is being referenced and whether the figure represents the internal battery or the output. The 5V rated output capacity also differs from the capacity that is ultimately stored in the device battery. MOT-MBSS10002 Capacity Indication

What Do W, V, A, Input, and Output Mean?

This schematic diagram separates the scenario of recharging the power bank from the scenario of supplying power to a device. You can read Input and Output in the specification table by paying attention to the direction of the arrows.

W (watts) represents power, V (volts) represents voltage, and A (amperes) represents current. While Wh indicates the amount of storable energy, W indicates the power supplied at that moment. For DC charging, it is calculated as W = V × A. For example, 9V and 2A equals 18W. NIST Definitions of Units for Power, Voltage, and Electric Current

Unit / Display	What It Represents	How to Read It in Specification Tables
mAh	Charge capacity	Read in combination with voltage and display standards
Wh	Energy	Used for comparing capacity between the unit and devices, and for airline regulations
W	Power	Check the corresponding power for each input and output
V	Voltage	Check whether the unit can supply the voltage required by the device
A	Current	Read the power in combination with the supported voltage
Input	Power accepted into the unit	Conditions for charging the power bank from a charger
Output	Power supplied from the unit	Conditions for charging a device from the power bank

You can check unit relationships at NIST. The roles of the power-supplying and power-receiving sides of USB-C are distinguished in the USB-IF specifications, and the input and output for each product are verified in the specification table. For specific examples of displays, refer to the MOT-MBSS10002 Instruction Manual.

If you compare V to water pressure and A to the size of the flow, W gives an idea close to the combined supply capacity of both. However, when comparing down to battery capacity, do not rely solely on this analogy—use Wh, which includes voltage.

Even if the maximum output in watts is large, it does not necessarily mean the device can receive that power. Fast charging is achieved only when the standards, voltage, and cable conditions supported by both the device and the power bank align. Charging speeds also vary depending on the device’s temperature and remaining battery level. USB-IF USB PD Explanation, Apple Fast Charging Conditions

How to Choose a Portable Charger: 5 Key Points

This is an image depicting the five check items before purchase. Capacity, output and standards, ports, size and weight, and safety are checked according to the devices you use and how you carry them.

Before purchasing, check the following five points in order. Once you determine the output, checking the input for charging the unit in succession allows you to consider both usage on the go and recharging at home.

1. Capacity: Does it provide sufficient replenishment amount and number of charges?
2. Output and Fast Charging Standards: Do they match the requirements of the devices and cables you use?
3. Port Types and Count: Does it meet the required number of connections and output when used simultaneously?
4. Size and Weight: Do they suit where you carry it and how you use it?
5. Safety: Can you verify the circle-PSE mark, the business operator, protection specifications, and recall or collection contact points?

Choosing Capacity Based on the Required Number of Charges and Portability

This is a self-made diagram illustrating how to read capacity indications. 10,000mAh, 3.7V, and 37Wh are fictional display examples and do not represent the specifications of any specific product. When considering the number of charges, also check the voltage conditions and Wh.

What you need is not a large number, but a capacity that can cover what you use while out. The energy required varies between short outings where you want to top up the remaining battery slightly and trips where you need to charge multiple devices at your destination.

Below are rough comparison ranges to help narrow down your capacity options. The boundaries between 5,000, 10,000, and 20,000 mAh overlap. Usage needs do not simply switch at those numbers; products in the same range should be compared individually by their voltage standards, output, dimensions, and mass.

Product Capacity Range	Easy-to-Imagine Usage	How to Determine Charge Count	Portability and Additional Checks
5,000 mAh or less	Short outings or emergency top-ups	Estimate the required replenishment amount from the device’s Wh	Compare actual dimensions and weight with storage locations like pockets
5,000 to 10,000 mAh	Daily carry, smartphone replenishment	Add a margin for conversion loss to the daily shortage or desired charge count	Check how it fits in a bag and the time required to recharge the unit itself
10,000 to 20,000 mAh	Multiple charges, smartphones and tablets	Total the Wh and required replenishment amount for each device you want to charge	Also check the output required for tablets and power distribution during simultaneous connections
20,000 mAh or more	Long trips, outdoor activities, laptops, home backup	Estimate required Wh based on the number of days and devices	Confirm laptop output requirements, airline regulations, and storage/inspection details

Capacity ranges and usages are guidelines to help organize your options. Please refer to the Ministry of Land, Infrastructure, Transport and Tourism guidelines for capacity conversion, the MOT-MBSS10002 instruction manual for specific examples of output capacity, and NITE safety guidance for storage and inspection.

The approximate number of charges is calculated as: Energy actually delivered to the device battery (Wh) ÷ Device battery capacity (Wh). When estimating from the Wh stored in the power bank itself, you must account for conversion and charging losses, as well as the power consumed to operate the device. Do not apply the same efficiency to all products; check the devices and conditions provided in the product’s output capacity and charge count descriptions. Voltage Conversion Efficiency and Usable Battery Energy

For example, if you assume you want to replenish a 5,000 mAh, 3.85V device from empty to fully charged twice, the amount stored in the device alone is 19.25Wh × 2 = 38.5Wh. A 37Wh power bank in the same hypothetical example falls short of that amount even before considering losses. By totaling the device-side Wh from the required number of charges, and then factoring in conversion/charging losses and in-use consumption, it becomes easier to organize conditions than by choosing based solely on the mAh indicated on the product. Wh Unit Conversion

If you top up your smartphone from a state where battery remains rather than taking it from empty to full every time, the amount required for a single charge also changes. Considering daily needs based on your usual shortfall and travel needs based on the number of days and opportunities to recharge will help you narrow down your options without increasing unnecessary luggage.

Matching Output and Fast Charging Standards to Device and Cable Conditions

Check the official device requirements, port output and standards of the power bank, and cable ratings in combination. Chargers used to recharge the power bank itself should be checked separately.

If you want to recharge quickly, choose a combination of device, portable charger, and cable. USB PD (USB Power Delivery) is a mechanism that negotiates the supplied power between compatible devices. QC (Quick Charge) is Qualcomm’s fast charging technology, which requires a combination of a compatible device and a charging source. USB-IF PD Explanation, Qualcomm Quick Charge FAQ

Rather than setting a flat wattage for all smartphones or all tablets, review the requirements by specific model as follows.

Device Type	Specific Examples of Official Requirements	How to Apply to Portable Charger Selection
Smartphone	Fast charging for iPhone Air and 17e requires 20W or higher, while fast charging for iPhone 17, 17 Pro, and 17 Pro Max (up to 50% in about 20 minutes) requires a 40W or higher adapter.	Start from the requirements of the specific model, and verify the USB PD output and cable. For Android devices, check the official requirements for each model.
Tablet	20W adapters have been bundled with models such as the 8th, 9th, and 10th generation iPad. Across the iPad lineup, chargers may not be included depending on the model, country, or region.	Avoid confusing the wattage of bundled accessories with the device’s maximum input, and check the power and cable requirements for the specific iPad in use.
Laptop	Recommended adapter examples include 30W for the 13-inch MacBook Air (2022 and later) and 140W for the 16-inch MacBook Pro (2021 and later).	Check the accurate recommended power supply for the model, USB PD power delivery conditions, and power consumption while in use.

Basis for each row: iPhone Fast Charging, Included Power Adapters for iPads and More, Mac Power Adapters. Apple’s time estimates depend on conditions such as the adapter used, settings, and environment.

The bundled wattage or recommended wattage of an adapter serves as a clue for choosing a power supply that matches your device. When selecting a portable charger, also cross-reference the port voltage and supported standards. For USB-C iPads, using a compatible adapter with a higher wattage than the included accessory may result in faster charging. Because laptops consume power even while running, consider both charging and operational requirements if you plan to use the device while it is connected. Charging USB-C iPads, Mac Power Delivery Conditions

For iPhone cables, use USB-C for iPhone 15 and later models, and USB-C to Lightning for earlier compatible models. Make sure not only that the connector fits, but also that the cable meets the required charging specifications. Apple Cable Requirements

To supply power exceeding 60W via USB PD, a 5A-compatible cable is required. For exceeding 100W, also check that the main unit, device, and cable all support EPR. Since some 5A-compatible cables are rated only up to 100W, you cannot assume a cable supports 240W simply based on a 5A rating. 240W is a specification condition of 48V and 5A. USB PD Specifications

Simply having a newer PD version does not mean all features or maximum output can be used. For those who want a detailed comparison, please also refer to the latter sections on The Relationship Between PD, PPS, AVS, and Cables and the Generation-by-Generation Timeline.

Conditions for recharging the portable charger itself are explained in detail under Checking Input, Charging Time, and Pass-Through.

Check Port Types/Counts and Power Distribution During Simultaneous Charging

Verify not just the port types, but also input/output roles, supported standards, the number of devices used simultaneously, and power distribution.

Taking the MOT-MBSS10002 as an example, this diagram compares single connection and two-device simultaneous distribution. This is specific to this product, so make sure not to apply the same distribution to other products.

If you want to charge a smartphone and earphones simultaneously via cable, you need an output capable of supplying power to both. Even if there are two terminals, if one is exclusively for the power bank’s input, you cannot use them the same way. In addition to the number of ports, check what each terminal is meant to connect to.

Terminal Name	Shape Reference	Connection Characteristics	What to Check for Device-side Input/Output	Examples of Connection Targets / Uses
USB Type-A	Rectangular port	With standard terminals, you plug them in matching the cable orientation.	Some power banks feature this for output use. Functionality is confirmed in product specifications.	Cables connecting the USB-A side to the main unit and the other side to a compatible device.
USB Type-C	Rounded, vertically symmetrical shape	Can be plugged in regardless of whether it is facing up or down.	Check whether it supports both input and output or just one direction, along with PD, PPS, and maximum wattage.	USB-C compatible smartphones, tablets, laptops, etc.
Lightning	Apple’s proprietary elongated terminal	Used to connect to compatible Apple devices.	Check whether it is an input terminal on the main unit or the device-side of a built-in cable.	Compatible models such as iPhone 14 and earlier.
Micro USB Type-B (USB 2.0)	Small shape with different top and bottom orientations	Plugged in by matching the orientation.	Check the intended use and input wattage, such as for main unit input.	Micro USB input power banks and compatible devices.

For specific examples of aligning terminal orientation, please refer to the Sanwa Supply instruction manual; for the relationship between USB-C shapes and supported features, the USB-IF guidelines; for specific examples of input/output markings on the main unit, the MOT-MBSS10002 instruction manual; and for iPhone connections, please refer to Apple’s guide. Terminal shape alone does not determine power delivery, input/output direction, or support for high-speed data transfer.

When using multiple outputs, do not simply add up the maximum single-port outputs; instead, read the simultaneous usage distribution table. For the MOT-MBSS10002, the conditions change as follows:

Connection Method	USB-C Output	USB-A Output	Total Output
Using USB-C only	Max 30W	Not used	Max 30W
Using USB-A only	Not used	Max 18W	Max 18W
Using USB-C and USB-A simultaneously	Max 18W	Max 12W	Max 30W

This is a specific example based on the MOT-MBSS10002 output specifications. It does not mean that USB-C 30W and USB-A 18W can be output simultaneously.

Products with built-in cables are candidates when you want to reduce the number of cables you carry. Check whether the terminals match your devices, whether the length and orientation reach your devices with a case attached, whether the cable can be replaced if damaged, and whether external ports can be used. If you plan to use your smartphone while holding it, ease of handling is also a criterion for selection. If you want to use wireless charging, be sure to check the latter section on Qi2 compatibility conditions as well.

Comparing Body Size and Weight Based on Actual Dimensions, Grip, and Required Capacity

For storage, consider the unit’s length, width, thickness, and other luggage; for handheld use, consider how it fits when stacked against your device and the position of the cables.

This is an image illustrating scenarios of carrying it in a pocket or bag. Check the dimensions, weight, and required capacity of both the unit and the storage space.

If you plan to put it in your pocket, check its thickness and width; if you plan to put it in a bag, check how it fits alongside your other belongings. If you plan to hold it in your hand stacked on top of your smartphone, look not just at the impression from photos, but at the actual dimensions of the unit and the position of the cables.

For daily use, a 10,000mAh model is one of the candidates, but it is not necessarily the right capacity for everyone. Your required capacity changes depending on whether you just need a little top-up until you get home or if you use your device heavily all day. Even among products with the same rated capacity, compare their dimensions, mass, ports, and built-in cables to choose the features that suit your specific usage style.

For extended trips or outdoor activities, in addition to meeting the required capacity and output, consider the usage and storage environment. Do not judge waterproofing or shock resistance solely by a rugged appearance—check the product’s official specifications if necessary.

When preparing for home emergencies, inspect the remaining charge and exterior in accordance with the instruction manual, and store the device away from high temperatures and direct sunlight. Avoid leaving it inside a vehicle. NITE storage and usage guidelines

If you want to see specific examples of compact models, please also refer to our article on USB-C connector built-in models. Compare them after organizing your required recharge amount and the connection method that fits your device and case.

Safety: Check for the Round PSE Mark, Registered Business Entity, Protection Specs, and Recalls

PSE marks come in two shapes: round and diamond. This self-created diagram organizes the items to check on applicable portable chargers in Japan, such as the round PSE mark and the name of the notified business entity. Also verify official support channels, protection specifications, recalls, and recycling policies together.

Safety should be chosen with consideration not only of pre-purchase labeling, but also throughout its active use and after disposal. Products using lithium-ion batteries can lead to heat generation or ignition due to defects or mishandling. It is important to verify the round PSE mark, business entity, protection specifications, recall status, and proper usage guidelines all together. NITE Portable Charger Safety Guide

For portable chargers subject to the Electrical Appliance and Material Safety Act sold within Japan, check for the round PSE mark and the name of the notified business entity. As a rule, these must be displayed in an easily visible location on the surface of the main unit, with exceptional conditions applying to packaging displays. The scope of applicable batteries and detailed labeling conditions are explained later in Supplementary Notes on PSE Labeling. Ordinance for Enforcement of the Electrical Appliance and Material Safety Act, Article 17, Appended Tables 5 and 7

Safety Check Item	Significance When Choosing	Where to Look Before Buying
Round PSE and Business Entity Display	Confirms required labeling for applicable electrical appliances in Japan	Display on the main unit and nearby business entity name. For packaging displays, also check exceptional conditions.
Protection Specs (Overcharge, Overdischarge, Temperature, Short Circuit)	Confirms which types of anomalies the product is designed to handle	Product specifications, instruction manuals, official support
Manufacturer/Vendor and Contact Information	Identifies who to consult in the event of a malfunction	Official channels, business information, warranty guide
Recalls and Recycling Policy	Links to inspections during use and post-disposal handling	Manufacturer’s important notices, recycling guides, JBRC eligibility criteria

Please refer to NITE and the Enforcement Ordinance for labeling and usage checks, and JBRC for recycling conditions.

Famous brands and review scores serve as helpful points of comparison, but safety cannot be judged by them alone. Check whether you can identify the model number and business operator at the point of purchase, and whether you can easily access official customer service contacts or recall information. Even with protective features in place, it is necessary to use the product in accordance with the instruction manual, such as avoiding high temperatures and strong impacts. NITE: Confirmation at the Time of Purchase and Use

The CE mark indicates conformity with applicable EU legislation, while FCC equipment authorization relates to technical requirements for radio frequency devices and the suppression of harmful interference. Because their scopes and procedures differ, battery safety cannot be compared based solely on the number of marks. European Commission CE Explanation, FCC Equipment Authorization Explanation

For any candidate product where you cannot verify the required labels or business operator at the time of purchase, re-compare it against products whose conditions can be clearly verified. Responses to abnormalities after you start using the product are explained in detail under Precautions for Use and Storage, and post-usage disposal is covered under Checking Collection Destinations.

Detailed Supplementary Information on Device Charging, Standards, Travel, and Safety

From here, we will organize the details regarding power bank charging conditions, fine differences in standards, handling during travel, regulatory labeling, and recycling conditions. If you want to check specific sections before making a purchase or read about how fast charging has evolved across generations, please open the two timelines below.

• If you want to use your existing charger: Go to Device Input, Charging Time, and Pass-Through.
• If you want a detailed comparison of fast-charging support: Go to PD, PPS, AVS, and Cables and PD & QC Timeline.
• If you are considering magnetic wireless charging or traveling: Go to Qi2 and Case Combinations and Airline Carry-On Conditions.
• If you want to prepare for long-term use: Go to PSE Marking, Abnormalities, and Storage and Collection Points.

Also Verifying Device Input, Charging Time, and Pass-Through

Match the charger’s output and the cable’s rating to the unit’s input requirements. Check the charging time in combination with the conditions listed in the instruction manual.

This image depicts checking the connection destination and charging sequence with the instruction manual at hand. The conditions for pass-through supported ports, priority order, and speed vary by product.

Even for products capable of delivering high power to devices, the power bank itself is not necessarily charged at that same wattage. It is important to read the Input and Output specs separately in the specification table. Especially when using the power bank daily while traveling, check whether it can be recharged within a time frame when you are around, and see which input options are compatible with your current charger.

For example, the input for the MOT-MBSS10002 is up to PD 30W, and using a PD 30W charger takes approximately 2 hours to go from empty to a full charge. This timeframe applies to that specific combination of product and charger. Even if you have a USB-C cable, it will not achieve the same results unless the charger itself supports the required PD output. MOT-MBSS10002 Input and Charging Time

Calculating the time by dividing Wh by the input wattage assumes that a constant amount of power continues to flow into the battery. Actual full-charge times involve voltage conversion losses and charging control that adjusts the voltage and current of the lithium-ion battery. Be sure to check the times and conditions in the instruction manual when making a purchase. Do not calculate the power bank’s charging time using the output wattage. Voltage Conversion Efficiency, Lithium-ion Battery Charging Control

USB-C input is a key point to check when you want to share compatible devices and cables. When considering a product with Micro USB input, you should also research the required cables and input conditions. Do not assume fast-charging support or safety based solely on the shape of the terminal; instead, read the product specifications and labeling. USB-C and Functional Differences

If you want to power your device while the unit itself is connected to a charger, check for pass-through support and the operational sequence. For example, with the MOT-MBSS10002, you connect USB-C to the charger and USB-A to the device, charging the connected device first before charging the main unit itself. With this product, charging speed decreases during pass-through. It does not necessarily mean the main unit and the device will always fully charge at the same time. MOT-MBSS10002 Pass-Through Operation

Before purchasing, check the instruction manual for available input/output ports, whether devices are prioritized or the main unit and devices are charged simultaneously, and the connection speeds or switching behavior. Even if you want to use it as an uninterruptible power supply (UPS), do not judge based solely on pass-through support; the device must specifically support that intended use.

How to choose a charging location and how to respond in case of an abnormality are summarized later in Usage and Storage Precautions.

If you also want to get the power supply for charging the main unit, organize your candidate input requirements and then check out how to choose a USB charger.

Detailed Relationship Between PD, PPS, AVS, SPR, EPR, and Cables

USB PD determines power-supplying conditions by having the power-supplying side and the receiving side exchange compatible voltage and current. A portable charger acts as the supplying side when powering a device and as the receiving side when charging its own internal battery. Even for products that use the same USB-C port for both directions, you should check the supported values for both input and output respectively. USB PD Specification

PPS is a mechanism that allows fine-grained requests for voltage and current, while AVS is a mechanism for adjusting voltage. SPR stands for Standard Power Range and EPR stands for Extended Power Range, with EPR handling power delivery exceeding 100W. Because these features depend on device implementation, you should read the supported features and voltage range in addition to the PD designation.

Term / Feature	Key Points for Reading Specifications	Pre-purchase Checks
SPR Fixed Voltage	Ranges up to a maximum of 100W at 20V and 5A. Max 60W with a 3A cable.	Check the common voltage between the unit and the device, and the required current.
PPS (Programmable Power Supply)	Voltage requests are in 20mV increments, and current requests are in 50mA increments. SPR PPS in current PD3.2 v1.2 starts at a minimum of 5V, with maximum supply voltage categories of 11V, 16V, and 21V.	Check whether the unit meets the PPS range required by the device.
SPR AVS (Adjustable Voltage Supply)	Handles 9 to 15V, and up to 20V depending on supported power. Voltage requests are in 100mV increments.	Check for AVS support and the voltage/power range of the product.
EPR Fixed Voltage / AVS	Fixed voltages of 28V, 36V, and 48V provide 140W, 180W, and 240W respectively at 5A. EPR AVS handles from 15V up to a supported maximum of 28V, 36V, or 48V, with voltage requests in 100mV increments.	Check EPR support for the unit, device, and cable, as well as their individual maximum wattages.

The table is based on the USB PD3.2 v1.2 specification confirmed on October 13, 2026. The usable range for each product should be verified in that product’s specifications. The USB-IF EPR Guide is also helpful as a reference.

For PPS, the voltage display of the APDO (Augmented Power Data Object)—which conveys the supplying side’s capabilities—is in 100mV units, whereas the voltage requested by the device during operation is in 20mV units. Make sure to distinguish between display increments and request increments. In the current specification, the supplying side’s maximum voltage is categorized into 11V, 16V, and 21V, while the receiving side’s maximum voltage expression range is 5 to 21V. AVS voltage requests are effectively in 100mV increments. USB PD Specification APDO and Request Data

PPS products based on older versions may list support starting from 3.3V. In the current PD3.2 v1.2, the minimum value for SPR PPS is 5V, and 3.3V is noted as deprecated legacy values. Do not reinterpret older product specifications using current version numbers; always verify the actual supported ranges of both the connected device and the power bank.

When choosing a cable, check the following conditions according to the required power.

• Up to 60W: The upper limit handled by USB PD 3A cables is 20V and 3A for 60W. Compatibility with both the power bank and the device is also required.
• Over 60W up to 100W: A 5A-compatible cable is required. There are also conditions where cable capabilities are identified using an e-marker or similar methods.
• Over 100W: Use an EPR-compatible cable in addition to 5A support, and verify that both the power bank and the device support EPR.

These are conditions outlined in the USB PD specification. You cannot assume compatibility with all voltages or 240W simply based on phrases like “USB-C,” “5A,” or “PD compatible.”

FRS (Fast Role Swap) is a mechanism that allows compatible hosts, relay accessories, and other devices to quickly switch power roles when external power is lost. There are conditions required for compatible devices and for initiating the role switch. USB Type-C Authentication (device and cable authentication communication) and firmware updates are also functions handled in related specifications and communications, requiring verification of support for each product. Neither FRS support nor PD support alone guarantees that a portable charger can be used as a UPS or that battery accidents will not occur. Related Specifications and FRS in the USB PD Specification

Dual Charge, used in QC, is a design that splits charging power internally within a device into two power management paths to dissipate heat. This does not mean that a portable charger has two output ports. Qualcomm’s Quick Charge 4+ Explanation

USB PD and Quick Charge Generation Chronology

Generation numbers are clues to understanding technological changes. When making a purchase, prioritize checking the features required by the devices you use and the input/output specifications of the product. Announcement timing, initial specification editions, dates of revised documents, and the timing of product releases all differ.

As confirmed on October 13, 2026, the current published version of USB PD is 3.2 v1.2. The initial release of v1.2 was in January 2026, the cover page of the archived revised PDF is dated August 19, 2026, and the posting date in the USB-IF document library is September 14, 2026. USB-IF Document Library, Specification Package

With Quick Charge, you cannot determine the release order based solely on the version numbers. For example, 3+ is a series introduced after 4+. Check which Quick Charge or USB PD pathways are supported by both the device and the charger. Qualcomm Quick Charge FAQ

Check Devices, Cases, and Certifications for Qi2 and Wireless Charging

This is an illustrative image showing combinations of devices, cases, and portable chargers. You check Qi2 compatibility and certification in combination with compatibility with your case.

If you want to use wireless charging, check that both your device and the portable charger support it. The first-generation Qi2 is up to 15W, while Qi2 25W is a generation based on Qi v2.2.1 supporting up to 25W. The WPC announced the rollout of Qi2 25W certification in July 2025. Seeing “Qi2” does not automatically mean all products support 25W. WPC Qi2 25W Announcement

What you need to check is device support, the portable charger’s wireless output, Qi2 certification, and compatibility with the case you use. Since Qi2 Ready also supports Qi2 via approved combinations of compatible devices and cases, you must verify up to that specific combination. WPC Qi2 Ready Explanation

The mere feature of magnetic attachment does not indicate whether a product has received Qi2 certification. Even for products with a high maximum wired output, you should check the maximum wireless output separately.

Charging speed is also affected by conditions such as the device and temperature. Consider whether you want to use it while holding it in your hand or place it on a desk to top up, and make your choice including wired connection options. WPC Qi2 Explanation, Apple Temperature and Fast Charging Conditions

Check Capacity, Quantity, and In-Flight Usage Conditions Before Bringing on a Airplane

This is an image organizing Japan’s application guidelines effective April 24, 2026. You can bring up to two units with a capacity of 160Wh or less per unit, though being allowed to bring them on board does not mean you can charge devices during the flight. Always check the latest conditions for the airline and route you are using as well.

If you are traveling by airplane, please check the Wh rating on the unit before purchasing. In Japan, the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) outlined the following conditions in its guidelines on portable chargers announced on April 14, and applied from April 24: MLIT Announcement

• Carry-on luggage is limited to up to two units, with each unit rated at 160Wh or less.
• They cannot be placed in checked baggage.
• Do not charge the portable charger itself inside the aircraft.
• Do not charge other electronic devices from the portable charger inside the aircraft.
• Take measures to prevent short circuits at the terminals, do not place them in overhead storage bins, and keep them with you.

Please also check the MLIT passenger guidelines regarding capacity labeling, short-circuit protection, and keeping devices with you. For example, converting from mAh to Wh requires the unit’s rated voltage. If the capacity cannot be read, do not assume that a device is permitted simply based on the mAh rating in the product name.

Before departure, be sure to also check the latest conditions for the airline and route you are using. In particular, if you are carrying spare batteries exceeding 100Wh, you need to check the combination limits in addition to the quantity limit for portable chargers alone.

According to ANA’s domestic flight guidelines, portable chargers exceeding 100Wh up to 160Wh and spare batteries in the same capacity range are limited to a combined total of up to two. Items exceeding 100Wh are counted separately from the general limit of two portable chargers. Typical combinations are as follows:

Portable chargers of 100Wh or less	Portable chargers exceeding 100Wh up to 160Wh	Additional spare batteries exceeding 100Wh up to 160Wh that can be added
2 units	0 units	Up to 2 units
1 unit	1 unit	Up to 1 unit
0 units	2 units	0 (Cannot be added)

This table is based on domestic flight examples from ANA’s guidelines for spare batteries and portable chargers. There are also conditions such as transporting spare batteries together with the electronic device body and preventing short circuits at individual terminals. This does not mean you can bring two portable chargers plus two additional spare batteries of any capacity.

Please prepare by distinguishing between general explanations for spare batteries and conditions specific to portable chargers. For international or connecting itineraries, please check according to the guidelines of each operating airline. MLIT Carry-on Guidelines

Scope of PSE Mark Display, and Precautions During Use and Storage

This is an image depicting a scene where charging is performed in a place within sight. Keep flammable materials and beverages away from the area, and choose a location where exposure to water can be prevented.

Appended Table 2, Item 12 of the Ordinance for Enforcement of the Electrical Appliance and Material Safety Act specifies that applicable lithium-ion storage batteries are those with a volumetric energy density of single cells of 400 Wh/L or more, excluding those used in automobiles, motor-driven bicycles, medical machinery and equipment, and industrial machinery and equipment. This refers to the energy density per unit volume of the battery cell and is a different standard from the Wh of the main unit confirmed when bringing it onto an airplane. Electrical Appliance and Material Safety Act Enforcement Ordinance

The display for applicable products relates to Article 17, Appended Table 5, and Appended Table 7 of the Enforcement Regulation. In principle, the circular PSE mark and the name of the notifying business entity, etc., must be displayed in close proximity to each other in a readily visible location on the surface of the main unit using a method that prevents easy erasure. Under certain conditions, approved abbreviations or registered trademarks that have been notified may be used in place of the business entity name. If it is difficult to display the information on the surface of the main unit, there is an exception to display the symbol and business entity name on the packaging. Ordinance for Enforcement of the Electrical Appliance and Material Safety Act

The circular PSE mark also does not imply uniform third-party certification or a guarantee of accident-free operation. When purchasing, be sure to check these displays and the manufacturer’s contact window. The CE mark relates to conformity assessment and declarations of conformity in accordance with applicable EU legislation and does not mean all-inclusive third-party certification. FCC equipment authorization also deals with technical requirements for radio frequency equipment, among other things. Understand the respective roles and consider preparations for battery accidents, including user manuals and recall information. Enforcement Regulation, European Commission CE Explanation, FCC System Explanation

While using the device, incorporate the following points into your daily checks:

• Place the device in a location within sight while charging. Avoid charging while sleeping, while away from home, or in situations where the device is unattended.
• Avoid high temperatures, direct sunlight, and strong impacts. Be careful not to leave the device inside a vehicle or use it after it has been dropped.
• Discontinue use if any abnormalities occur, such as the device becoming abnormally hot compared to before, swelling, or sustaining damage. Do not continue charging as-is, and consult the manufacturer or other appropriate point of contact.
• Check for recalls associated with specific model numbers. For products that have been used for a long time or are stored at home, inspect their external appearance and remaining charge in accordance with the user manual.
• Do not attempt to disassemble the device yourself or dispose of it with general household waste. Check the manufacturer’s or local municipal guidelines for proper disposal methods.

In the event of smoke generation or fire, prioritize ensuring your own safety first. Do not approach the main unit if smoke or flames are erupting, and call 119 if dealing with the situation is difficult. Differentiate between consulting the manufacturer regarding everyday abnormalities and the appropriate response in the event of a fire. NITE Guidance on Fire Responses

For usage, storage, and handling during abnormalities, please refer to the NITE Safety Guide, and for cautions regarding high temperatures and impacts, please refer to the Consumer Affairs Agency Guide.

Even for products bearing the circular PSE mark and safety function indications, it is important to use them while monitoring their condition. Choosing products for which the manufacturer’s official support contact is clear allows you to consult with them if any abnormalities are found or when you are finished using the product.

Where to drop off used power banks and where to consult for ineligible items

Check the JBRC eligibility conditions, and insulate the terminals without disassembling the main unit. Do not place swollen, damaged, water-damaged, non-member, or unknown manufacturer products into regular collection boxes; instead, consult the manufacturer or local municipality.

For used power banks, be sure to check the eligibility conditions of the drop-off location before bringing them in. JBRC recycling generally requires that all of the following conditions be met: JBRC recycling eligibility and non-eligibility explanation

• It must be a product from a JBRC member company.
• The type of battery must be identifiable.
• It must meet collection conditions, meaning there are no abnormalities such as damage, water damage, or swelling.

Target power banks whose primary function is charging smartphones and other devices are collected as-is as a whole unit, so do not disassemble them to remove the battery. Insulate the terminals and bring them in following the instructions of cooperating stores or municipalities. Simply having a recycle mark does not make it eligible; you must verify the member company, battery type, and condition. JBRC whole-unit collection and terminal insulation guide

For units that do not meet the above conditions, inform the manufacturer or local municipality of the model number and condition, and dispose of them according to the instructed method. If the manufacturer is unknown, also consult your local municipality, and do not mix them with regular household waste. JBRC ineligible conditions, NITE disposal guide

The JBRC member list confirmed on October 13, 2026, includes Anker Japan Co., Ltd., CIO Co., Ltd., ELECOM Co., Ltd., and Buffalo Inc. However, even for products from member companies, there are collection conditions such as the battery type and condition. Checking a manufacturer’s recycling policy before purchase allows you to determine where to seek support after the product’s useful life. JBRC member company list

Summary: Choose the Right Capacity, Output, and Safety Features for Your Needs

Portable chargers are easier to choose when you start with your devices and usage scenarios, then check capacity, output, standards, ports, size and weight, and safety. Be sure to align voltage conditions for capacity, and evaluate output by combining device and cable compatibility.

Usage Scenario	What to Determine First	What to Check Last
Short outings for quick top-ups	Amount of charge needed, device terminals	Actual dimensions and weight to fit your carrying case
Daily carry	Daily power deficit, required fast charging	Charger input, your existing charger, recharge time
Laptops and multiple devices	Wh rating and charging conditions for each device, number of connections	Single-port output and simultaneous distribution, cable ratings
Travel and home preparedness	Number of days, charging opportunities, storage environment	Airline regulations, inspection of exterior and remaining charge, recycling drop-off points

When reading capacity and input/output specifications, refer to the MOT-MBSS10002 specification example mentioned above. You can check airline carry-on conditions in the Ministry of Land, Infrastructure, Transport and Tourism aviation guide, and safety, storage, and inspection guidelines in the NITE safety guide.

Before purchasing, also verify the circular PSE mark, manufacturer/importer information, official customer support channels, and recall or disposal policies. If a candidate product lacks verifiable Wh ratings, output specs, device compatibility, labeling, or business operator info, compare it against alternatives with clear specifications.

If you would like to see specific examples of high-capacity and high-output models, please organize the requirements of the laptop or devices you plan to use and refer to this article as well.

First, check the model numbers and charging conditions of your devices, and compare them against the specifications of your candidate products. If you plan to travel by airplane, please also refer to the Ministry of Land, Infrastructure, Transport and Tourism’s carry-on guide, and if you want to check disposal and recycling options, please consult the JBRC eligibility conditions and collection point guide to prepare for everything from initial use to eventual disposal.

Thank you for reading until the end!

• The evaluation in this article is unique to this site.
• Unless otherwise specified, product prices and information are current as of the time of writing.
• Please note that this site cannot be held responsible for any inaccuracies in this information.
• Product and service names mentioned on this site are trademarks of their respective companies.

This article was originally written in Japanese and has been translated.