Power bank charging port. Author

How to Prototype a Power Bank Charger Without Building Any Dedicated Hardware

The short answer to this question is yes, and, as this question has been asked by many customers over the years, this article was written to explore the topic in further detail. This article will review the process involved in developing an application using existing evaluation boards, discuss the challenges encountered, and outline recommendations for further revisions and improvements.


Ideally, any power supply design should start with some basic proof of concept tests, which often involve testing an existing demo board. This demo simply takes this preexisting step (of testing single rails on the demo hardware) and expands on it to produce a working system using demo hardware. Furthermore, as this demo was needed within a relatively short time frame, the typical development process of design, layout, build, assemble, and test (plus any design iteration) was not possible, so the system was prototyped in its entirety using nothing but readily available hardware.


To answer the question posed at the beginning of this article, it was necessary to choose a high level application as a starting point to prove this was possible. This led to the power bank charging application being selected as a proof of concept. As power management is a prerequisite for every electronic project, any other application could have been selected.

A power bank charger is a common enough application, which most consumers have encountered and used—for example, many travelers carry one to ensure their phone remains charged over a long journey. A power bank is essentially a battery pack (capacity varies depending on the price and range required), with one or more USB-A ports as well as a USB-C input port to charge it. It is possible of course to layer additional complexity on top of this basic functionality—for example, the addition of a wireless charging pad or an input to allow solar charging of the bank for outdoor enthusiasts.

For this application, the option to charge the battery via solar or to charge via a DC input from a standard 12 V AC-to-DC wall wart was included. The outputs included some basic USB-A charging ports (two in total), producing 5 V for use with mobile phones and a range of USB-powered electronics.

Power Source Selection—LTC4416

In this example, the design will support two input power sources (a solar panel and an AC-to-DC wall wart, which is just a simple AC-to-DC power supply). For this reason, a clever device called a power path prioritizer is required not only to intelligently switch between the available sources depending on which was available but also to manage the situation where they both were available by assigning priority to one source or the other. A simple version of this implementation can be achieved by using some simple diodes—commonly connecting the two cathodes of the diodes and connecting the anodes to their respective sources. Unfortunately, this particular configuration is lossy due to the diode drop inherent in a typical diode (approximately 0.6 V), but it also doesn’t allow for any clever selection criteria to be implemented, for example, priority selection. It simply allows the higher potential input to pass through.

Here LTC4416 comes into play—it not only replaces the lossy diodes with PFETs, which are far more efficient, but also allows for priority to be assigned. In this particular application, priority will always be assigned to the wall wart. This allows the design to take advantage of the available power (and higher current) when it is available. This device is exceptionally flexible, with many operational modes possible depending on the design requirements. Table 1 (sourced from the LTC4416 data sheet) displays the modes of operation.

Basic power bank usage

Power banks are generally very easy to use, and typically conform to some simple conventions, especially with respect to the connectors.

Normally power bank connectors have separate functions and the two connectors used for these functions are very different, making it easy to differentiate them.

  • Micro USB (sometimes mini-USB): Most commonly a power bank will use a micro-USB for being charged. This enables the standard USB A to micro-USB leads to be used to charge the power bank. Often the same lead used to charge a mobile phone or other device can be used.
  • USB Type A connector: The larger type A USB connector is used to enable the power bank to charge other devices. This means that standard charging cables supplied with most phones and other devices can be used. Normal USB chargers have a Type A connector from which the charge is supplied.

When using the power bank, it is normally only necessary to connect a powered USB micro connector to it for it to receive charge.

Depending on the power bank capacity, its charge level, and the charger, the ambient temperature, etc., it can take quite a while to complete its charge.

As an example, a 1500mAh rated power bank should take very roughly about the same time as a typical smartphone to charge. For larger power banks, this time can be considerably increased. it may take two three, four. times as long.

Power banks have electronic battery management and this includes a safety cut-off to prevent overcharging and overheating. However, whenever possible, it is best to remove the power bank from charger when it is full. at least avoid leaving it connected long-term after its full.

power, bank, charging, port

However when using the power bank to charge electronic devices, the leads need to be connected, and it is normally necessary to use a button on the power bank to enable the charging. This is required because a sort circuit on the output of the power bank could generate a lot of heat and possibly cause the power bank to catch fire or explode.

This prevents keys in s (if the power bank is carried in a ) and other metallic items causing an accidental short circuit, and the output normally has to be enabled before use.

Often the power bank will have a simple LED indicator showing the level of charge it has when charging is enabled, or when it is being charged. These indicators often turn off after a short while to preserve the power bank charge.

Power bank charge capacity

One of the key aspects, when buying a power bank is to ensure that it has sufficient capacity to provide a charge for the device to be charged.

power, bank, charging, port

One of the most common uses for power banks is to charge mobile phones whilst on the move when there are unlikely to be any suitable charge points.

With modern mobile phone internal batteries now being able to store large amounts of charge (some are over 2500mAh), it is necessary that the power bank has in excess of this if it is to give the mobile phone battery a full charge.

It is also necessary to remember that the charging process is not 100% efficient. some of the supplied power is dissipated as heat, etc.

As a result the power bank should have a slightly larger capacity than the phone battery if it is to give it a full charge.

If the power bank has a smaller charge capacity than the phone, it will only be able to give it a partial charge. this may be acceptable in some instances if the power bank is only needed to top-up the main phone battery.

Power bank care: usage hints, tips guidelines

In order to get the best from any power bank there are a few guidelines that will help ensure the performance is gained from the power bank for as long as possible.

  • Keep at room temperature: The best performance can be obtained from a power bank if it is kept at around room temperature. While this may not be possible all the time, it is wise to use this as a general guideline. The battery technology used in power banks is lithium ion, and these batteries do not like getting excessively cold, or too warm either. One of the key things to remember is that they should not be left in automobiles. In the summer sun the inside of cars can rise to in excess of 50°C, and in winter the cars have no heating when they are not in use, so the temperatures can fall really low in some places. Either scenario is not good for lithium rechargeables.
  • Charge before first use: Manufacturers always recommend giving a new power bank a full charge before use. The internal circuits will cut out the excess charge, but it is always wise to get it into a known state before starting to use it.
  • Keep the battery charged: This may sound obvious, but the power bank is no use if it is not charged up. It helps to get used to charging it up as soon as possible after it has been used. In this way it will always be ready for use.
  • Charge the power bank when not used for period: Lithium ion and lithium polymer rechargeable batteries do not like being left in a fully discharged state for long periods. As batteries will always lose a little charge with time, it is best to periodically recharge the power banks when they have not been used for some while. This means they are ready for use and the battery is kept in tip op condition. The ideal state for a lithium ion battery is neither fully charged or discharged, so if possible keep it in an approximate mid-charge state if it is to be left for a long period.
  • Only use power bank in the intended way: This may sound obvious, but a power bank should only ever be used for charging the type of device for which it is intended. Some devices may have different voltages, although if they have a USB connection this would not be the case. Also large devices may draw too much current from a small power bank and the like.
  • Keep away from moisture: Power banks are electronic devices, and therefore they do not like water, or even moisture. One key piece of advice when using power banks is to keep them dry at all times. With the amount of power within the power bank, moisture can cause significant damage.
  • Don’t keep in or bag with metal objects: In view of the amount of power held within power banks, and the possibility of short circuit, one very important aspect of using power banks is to make sure they are never shorted. Although power banks normally have a button which needs to be pressed to enable the supply on the output, it is always best to be careful and make sure they are never placed in a position where metal objects could short the output. Putting them in a alongside keys is a definite “No No.”
  • Don’t drop it: Power banks incorporate circuit boards as well as the battery. Like any other item of electronic equipment they need to be handled with some care. Dropping them can damage the case, the circuit board, or even the lithium rechargeable battery element itself. Take care when handling them.

Power bank rechargeable batteries are very easy to use. With a few sensible precautions they are really accommodating and provide additional charge when you are on the go and don’t have access to mains power.

One of the main points to remember, is to keep them charged. This is sometimes easier said than done, but there is no use having it if it is not recharged as soon as possible after it has been used.

ROMOSS OM10 Power Bank With Double USB Port Cable External Battery Pack Travel Size Portable Charger 10000mAh

Specifications : Size: L9.45CMW6.9CMH2.4CM Color: White Weight without package : 213g Capacity : 10000mAh Notice : For first use, please drain up the power bank to 0 before charging it to 100% to activate the digital LED screen.

For smooth customs clearance, customers from Korea who buy ROMOSS power bank, please leave your Clearance Code(P12 digits, such as P123456789235) when you place the order. Do not worry about that we will not disclose your information.

【Small Size Large Capacity】

One of the slimmest and lightest 10000mAh portable chargers.You can put it in backpack or even your while charging your phone.Work with all of for iPhone/for iPad/Tablets, other cell phones and electronic devices.It can charge about 4.3 times for iPhone 8 Plus,about 2.4 times for Huawei P10,about 1.2 times for iPad mini2.Suitable everyday use,flights,traveling,or going party.

3-input: Micro-USB, lighting and Type-C provides high convenience of recharging this power bank with any of these 3 widely used cables. 2-Output: 2 USB outputs enable to charge a mobile phone, a tablet or a Nintendo Switch simultaneously.

This portable power bank has a full-view LED display, it presents available battery percentage exactly. Ensures easy check and accurate battery capacity.

With built-in polymer cells are complaint with Civil Aviation Standards are allowed on aboard flight without any safety concerns.

【Quality Assurance Certified Safe】

Our Li-Polymer batteries adhere to the highest safety and quality standards.Automatically adjust the output power to deliver the optimal charging current keep your devices from overcharging, over-current, over-voltage and short circuit.

Designed with the purpose of environment protection, CABLE IS NOT INCLUDED.

ROMOSS SW20 Pro Portable Power Bank Charger External Battery PD 3.0 Fast Charging With LED Display

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power, bank, charging, port


  • ROMOSS Power Bank 60000mAh Powerful QC18W 22.5W SCP Fast Charge External Battery 90.99
  • ROMOSS Power Bank 65W PD Fast Charge 40000mAh USB C Portable Powerful Powerbank 55.66
  • ROMOSS 65W Fast Charge USB Type C Charger QC 3.0 PD 3.0 Quick Charger 22.99
  • ROMOSS Sense6PS PRO Power Bank 30W Fast Charger 20000mAh External Battery Portable Charger Powerbank 46.13
  • Romoss Power Bank 10000mAh PD 20W Fast Charging External Battery 10000 mAh Portable Charger Mini Powerbank 25.99

Input Charging

For recharging, you can use the USB-C or Micro-USB port to recharge the power bank. You can use either input to recharge it because both ports recharge the power bank at 18W. The USB-C port may be more accessible to recharge as the Micro-USB is a rather old port. An 18W input for a 10,000mAh capacity is good enough.

Besides the charging power, one of the top reasons to get this power bank is its size and weight. This charger has a length of 5.9 inches, a width of 3.6 inches, and a thickness of 0.6 inches. It weighs 8 ounces.

So this power bank is smaller than most phones, and the slim form factor allows you to easily place it into your

It’s just like using any other modern power bank. Charging automatically starts once you plug a device into the ports. A power button to the side can turn on the top screen, showing the remaining capacity and fast charging status.


The PowerAdd Pro 10,000mAh power bank is most reliable for charging phones and tablets; however, more so for phones as the capacity is pretty low. Also, the charging power fits into fast charging phones, including iPhones and Android phones, as the 20W USB-C Power Delivery is compatible with fast charging of both types. This power bank is not meant for charging laptops as 20W of Power Delivery is not very much.

Also, the small and slim form factor is another major reliable factor because this power bank is about the size of a phone and can easily fit into the same you have your phone in.


If you’re searching for an affordable mini fast charging 10,000mAh power bank, this PowerAdd Pro charger is a great choice. Enough capacity to charge most phones to full power at least once, two fast charging ports, fast recharging, and a slim form factor that you can take anywhere.

  • ⚡【PD 20W Power Delivery】This 10000mAh portable charger with type C output provides PD 20W fast charging, which can charge your phone to 50% in 30 minutes, bringing you a different fast charging experience.
  • ⚡【Dual Input Output】Unlike most power banks only with USB C input, this power bank with USB C 18W input and 20W output is perfect for your new iPhone, iPad and all other USB C devices. There are also USB 18W output and micro USB 18W input, giving you more possibilities.
  • ⚡ 【LED Display 】Unlike those vague blinking lights, this 10000mAh portable charger has a LED display, and the display will show the exact percentage of the remaining power, so you can keep track of the current power at any time. On the premise of supporting two-way fast charging, the word FAST is displayed on the screen.
  • ⚡【Convenient and Practical】This power bank fits easily in your s or bags. It is very convenient and practical for your daily life and outdoor activities. Gives you enough power for a whole day, enough to provide iPhone 13 with 2 Charges, Galaxy S21 with 1.5 Charges, Huawei P50 with 1.5 Charges.
  • ⚡ 【Broad Compatibility】This LED Display 10000mAh power bank is not only suitable for all mobile phones, tablets, but also for your low-current devices such as Airpods, bluetooth headphones, Smart watches etc.

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