I am looking for a power bank or battery extension for my laptop.

Introduction

Traditionally, power banks were mainly used for charging mobile phones and tablets through USB-C, Lightning, or Micro-USB connections. However, recently, larger power banks have been developed specifically to charge laptops. This article details the types of products suitable for this purpose and provides external product lists for guidance.

USB-C power banks with Power Delivery (USB-PD)

As mentioned in previous FAQs, most XMG and SCHENKER laptops can now be charged via USB-C or Thunderbolt, requiring a USB-C charger that supports the “Power Delivery” (USB-PD) standard and can output up to 20 volts. The required power (wattage) depends on the laptop model, with specifics provided in the laptop’s datasheet. A power bank with the appropriate USB-C specifications can be used in the same way like a cabled or wall-mounted USB-C charger. However, it’s important to note:

Some budget power bank models, though advertised as USB-PD compatible, may only provide up to 12 volts, which is insufficient for our laptops that require a 20-volt output.
The maximum output voltage of a power bank is usually stated on the product page or in the manufacturer’s datasheet.

Power banks advertising an output of 60 watts or more usually support a 20-volt output. Therefore, it’s advisable not to consider power banks with less than 60 watts of output. Additionally, some laptops require 100 watts to charge the battery while the laptop is in use (i.e. not just when turned off). It is, therefore, beneficial to opt for a power bank with as high an output as possible.

When searching for such a power bank, it is crucial to ensure:

Support for “Power Delivery” (USB-PD) and a minimum of 60 watts output.
As high an output power (watts – W) as possible
As high a capacity (watt-hours – Wh) as possible.

Suitable search filters can be found on the product comparison site Geizhals, where power banks are listed under “Mobile Chargers”. The following links are in German, but they will give you an idea of what kind of products are available. You can then look for the same products in a retailer in your region.

How much output power do I really need?

Due to the universal compatibility of USB-C, theoretically, all power banks listed under the provided links should work with our laptops that support USB-C charging. However, due to the variance in USB power supply (20 volts are not always exactly 20 volts; the value often fluctuates in practice), occasional incompatibilities cannot be entirely ruled out. Under this aspect, it may be worth opting for a higher-quality product with greater output power and capacity. Caution is advised with especially compact devices: the smaller the device, the more likely it is to overheat or experience fluctuations in output voltage.

Therefore, we advocate the following principles:

Overprovisioning is better than underprovisioning.
Compatibility and safety are more important than compactness and light weight.

What if the output power of the power source exceeds the laptop’s requirements?

There is no safety risk in using a particularly powerful power bank with a less demanding laptop: the laptop communicates to the power source how much energy it requires, not the other way around. This applies to laptop power adapters, chargers, docking stations, etc., whether via USB-C or traditional barrel plug connectors.

Alternative approach: power bank with barrel plug output

Some of the more potent power banks, in addition to USB-C, also have an analog output with a DC barrel plug connector, also known as a “barrel plug.” Such power banks typically come with a range of barrel plug adapters for different laptop types. These plugs connect to the laptop’s standard power input. For laptops that do not support USB-C Power Delivery, this approach is the only way to connect a power bank.

Which barrel plugs are compatible with our laptops is detailed in this article:

Are the power plugs of XMG laptops based on any industry standard?

Power banks with barrel plug output usually support operation from 19.5 to 20 volts and are thus suitable for laptops. However, the maximum output power of the power bank will be significantly below what the laptop’s original power adapter provides. Under load, this results in underprovisioning. The same rules as in the article on travel adapters apply here:

Can I use a smaller/lighter power adapter or charger for travelling?

In short: operating a laptop on a power bank with an analog barrel plug output (DC output) means the laptop does not know how much power is available through this energy source. The laptop initially assumes it is connected to the original power adapter and behaves accordingly. If the laptop demands too much power (e.g., through the use of a high-performance profile, activating the dedicated graphics card, or high CPU load while simultaneously charging the battery), the power bank may be overwhelmed and, if properly designed, will shut off.

In the worst case, or with cheap or poorly designed power banks, overheating at the power bank or the laptop’s power input may occur.

Such operation is therefore only recommended for particularly experienced users who know exactly how to limit the laptop’s power consumption during operation.

Special case: adapting USB-C to barrel plugs

In theory, USB-C power sources can also be adapted to analog barrel plugs. However, this introduces an additional potential uncertainty, including tolerance fluctuations and random incompatibilities. This route is therefore only recommended in exceptional cases or for particularly patient tinkerers. An exemplary documentation of such a setup can be found in this forum post with the following products: Power Bank + Magnetic Adapter + Barrel Plug Adapter. The forum participant reports that they had to try various theoretically compatible products before finding a configuration that worked.

A few steps up: power stations with 110/230V outlets

As an alternative to compact power banks, there are also power stations, primarily used in camping and at least the size of a briefcase. While a power bank provides a direct current (DC) source of up to 20 volts, a power station offers an alternating current (AC) source of up to 230 volts. This corresponds to the specifications of a standard wall outlet, to which a power strip or the original laptop power adapter can be connected.

The original chargers of laptops, mobile phones, tablets, and similar electronics can generally handle an AC power source between 110 volts and 230 volts. The 110 volts are common in the USA, and 230 volts in Europe. Therefore, a power station does not necessarily have to support 230 volts – for operation with a laptop power adapter, even 110 volts are sufficient.

(Hair dryers, kitchen appliances, heating blankets, lamps, etc., are not so flexible. They require a specific voltage, such as 230 volts, that is common in the sales region.)

In general, converting from high to low voltage is associated with conversion losses. These losses manifest as heat at the power adapter. Thus, operating a 20V laptop on a 230V power station is overall less efficient than on a power bank that directly outputs 20 volts. On the other hand, power stations are available with significantly higher total capacities. It, therefore, depends on how long and with what kind of computing performance one wants to operate a laptop independently of the power grid.

Such power stations can be found under the term “Solar generator” (Geizhals filter) or without solar power input simply as “Powerstation” (Amazon category). For even larger options, in Germany, there is the industrial customer provider Instagrid, whose products are designed, for example, for operation on construction sites.