Laptop Power Bank – Buying Guide

On top of charging mobiles, tablets and other gadgets, did you know that you can use a power bank to charge a laptop?

If your laptop is going to run out of battery and you do not have its charger at hand you can resort to a power bank to continue working or you can also use it as an external battery if the battery of your laptop is broken and you always need to have an outlet nearby.

A power bank can perform the same function as a laptop charger but not just any model will do, it must meet a number of requirements to work as a substitute for the charger:

  1. Connector: include a cable with a connector compatible with the laptop’s charging port.
  2. Voltage (V): same working voltage.
  3. Power (W): same or greater power supplied.

In this Guide we will learn how to identify a laptop power bank taking into account the above requirements and, as always, we will recommend the best models available on Amazon.

Features of a laptop charger

First of all, we need to know the specifications of our laptop charger in order to find a power bank that meets the same requirements.

In the following image we can see the specifications of a laptop charger:

Technical specifications of a laptop charger
Technical specifications of a laptop charger

We must check the output parameters (Output):

  • Voltage: 19.5V
  • Current/Amperage: 4.62A

This means that this charger works at a voltage of 19.5V (volts) and supplies a maximum current of 4.26A (amps).

This charger does not indicate the maximum power that it can supply but we can easily obtain it by multiplying the voltage by the current:

  • Power: 19,5V x 4,62A = 90W

With this information we already know the charging voltage (19.5V) of our laptop and the recommended power (90W) that our power bank should supply.

It is very important to know this voltage, because if we connect it to a charger (or power bank) that works at a higher voltage we could damage it irreversibly.

Using a power bank as a laptop charger

Next, we need to find a power bank that replaces our charger and meets the following characteristics:

Charging port

A laptop can be powered through a power bank in 3 different ways, depending on the OUTPUT port it has:

Types of laptop power banks with DC, AC and USB-C PD output ports
Types of laptop power banks with DC, AC and USB-C PD output ports

There are 3 types of laptop power banks on the market:

1. Power bank with DC port

If we use a specific power bank with a DC output it is important to check its output voltage and if it includes a connector compatible with the charging port of your laptop.

Although, generally, this type of models usually includes a set of adapters compatible with the main laptop brands:

Power bank con 2 puertos de salida DC

Their main disadvantages are the difficulty in finding a model compatible with a computer (output voltage or connector), they are bulky and require an AC charger to recharge them (like a laptop charger).

2. Power bank with an AC port

Another option are those power banks that include a 220V AC port.

In this case, we do not have to worry about incompatibilities since we can directly connect the charger of our laptop (or any other device) as if we were doing it to the plug of our house. Sounds good right?

Power banks with an AC 220V output port
Power banks with an AC 220V output port

However, there are also some drawbacks:

Large dimensions, additional AC charger and also some of the power from the power bank is lost when using the charger of the device (in this case the laptop) as a โ€œmiddle-manโ€.

3. Power bank with USB-C PD port

A new way to power your laptop is by using a power bank with USB-C output port with Power Delivery charging technology.

Power banks with USB-C PD output port
Power banks with USB-C PD output port

USB Type-C (USB-C) is the future of connectivity, allowing you to connect and charge any type of device (mobile, tablet, laptop, cameras…) using a single universal power port, forget about searching for cables and compatible connectors.

On the other hand, Power Delivery (PD) is the technology that allows powering high-power devices – such as a laptop, through the USB-C port.

USB Power Delivery ejemplos de uso

Nowadays there are many new generation laptops that use USB Type-C as a power port. In these cases, you simply need to look for a power bank with Power Delivery that is compatible with the charging voltage of your laptop.

But, what if my laptop does not have a USB-C charging port?

Is it possible to charge it with a power bank with USB-C PD?

Laptop with DC port vs. USB-C port
Laptop with DC port vs. USB-C port

We are aware that many users do not have a last generation laptop, in this case we would need to use a special adapter or cable that has a USB-C connector (power bank) on one end and an INPUT DC connector (laptop) on the other end.

Adapter and cable from USB-C PD to DC connector
Adapter and cable from USB-C PD to DC connector

This adapter or cable incorporates a trigger capable of demanding power in Power Delivery to the power bank at a certain voltage: in principle, we have found 2 models for 15V and 20V, we do not know if in the future they will be manufactured at other voltages.

For this reason, we must pay of attention to the voltage when buying this cable, since if we make a mistake in choosing it we could seriously damage our laptop.

For example:

If we connect a 15V PD trigger cable to a laptop charging at 20V, it will not be able to start charging => for a 20V laptop we need a 20V PD trigger cable.

On the other hand, if we connect a 20V PD trigger cable to a laptop charging at 15V, WE COULD IRREVERSIBLY DAMAGE OUR LAPTOP => for a 15V laptop we need a 15V PD trigger cable.

Output port voltage (V) โ—

If we choose to buy a power bank with DC or USB-C PD output it is very important to check that the output port of the power bank has the same voltage* as your laptop charger, otherwise you could irreversibly damage your computer.

This output voltage will always be indicated in the power bank specifications as “DC Output” or “USB-C Output”.

Output voltage on power banks with DC and USB-C PD port
Output voltage on power banks with DC port (left) and USB-C PD (right)
What happens if my laptop charges at a voltage of 19.5V*?

Actually any electronic device must withstand a voltage of +-10% of its nominal voltage, that is:

If your laptop charges at 19.5V, it can take a maximum voltage of 21.45V (19.5V+1.95V), therefore, a 20V power bank could be connected to it.

In addition, it is necessary to take into account the voltage drop that occurs in the cable connecting the power bank and the laptop, which varies between 0.15 and 0.2V (depending on the resistance of the cable itself) for each meter of length.

For example, if the output voltage of the power bank is 20V, the laptop would receive a voltage of 19.8V (20V-0.2V).

On the other hand, we can also find models that may have one or more DC output ports with a fixed voltage or a single multi-voltage DC port, whose voltage can be selected (by pressing the “Power” button) to the charging voltage of our laptop.

Power bank with multi-voltage DC port
Left: Power bank with 2 fixed voltage DC ports: 12V and 20V Right: Power bank with multi-voltage DC port: 9V/12V/16V/19V/20V

Obviously, if we were to use a power bank with AC output it is not necessary to check the voltage because we would continue to power the laptop with its own charger (which is already in charge of transforming the 220V voltage to the computer charging voltage).

Power supplied (W)

Finally, we must take into account the maximum power that can be supplied by the output port of the power bank:

Maximum power in laptop power banks
Maximum power in power banks with DC (130W), AC (85W) and USB-C PD (45W) output ports respectively.

If the charger of our laptop is 65W then it is advisable to use a power bank that is capable of providing the same or higher power than the charger, because, otherwise, the computer would not even start up as it needs the maximum power during its start-up (and subsequent use) at the same time as it recharges its battery.

However, in the following section we will look at some situations in which it is possible to use a lower power model:

How much power does a power bank need to charge a laptop?

Depending on the laptop model, your charger will be designed to supply a maximum amount of power, i. e: 45, 65, 90 or 130W.

We may not find a power bank that provides the same or a higher amount power than our portable charger either by specifications or budget. In this situation, we can also buy a lower powered power bank.

Let’s say we are working in a coffee shop with our Lenovo Z50-70 laptop (its charger is 65W) and we run out of battery.

We could use a 65W power bank or resort to a lower power one, for example, 45W, to be used under certain conditions:

1. Removing the laptop battery

If we remove the battery from the laptop, the power of the power bank needed to continue working with the laptop will be lower than the power provided by its charger, since in this case, the energy needed to recharge its battery is not necessary.

We should also consider, that the power required during the start-up of a computer is always higher than the average working power, due to the extra current peak that is produced.

A little trick to avoid the current peak at start-up would be to activate the sleep mode when the computer indicates that its battery is running low. (Normally it goes to sleep a few seconds after closing the lid, if the laptop has been configured this way).

Next, we connect the power bank and then remove the battery from the laptop.

If we deactivate the sleep mode (open the lid) right now, we could enjoy the power from the power bank without “suffering” that power peak at start-up.

In this scenario, we could use a power bank that supplies at least 70% of the power of our laptop charger. That is to say, if our charger is 65W, the power of the power bank should be at least 45W.

2. Recharging the battery while the laptop is turned off

Another option would be to keep the laptop turned off while recharging.

In this case, we would only need the power required to recharge the laptop battery and we could use the same power bank as in the previous case (45W), i.e., supplying at least 70% of the power of our laptop charger.

3. Recharging the laptop while using it at the same time

If the 2 previous options do not convince you, it is possible to use a lower powered power bank when the computer battery is not completely discharged (usually less charging power is required after 50% battery).

This way, if we connect the power bank before the laptop battery is depleted, we also avoid excess power at the start-up peak.

The problem lies in knowing the starting peak of our laptop and knowing how much power it needs to recharge its battery when it is still half-charged. Measurements would have to be made and this is usually not within everyone’s reach.

For this reason, we think that the most advisable thing to do is to use a power bank with the same or higher power than the laptop charger in these scenarios.

Best power banks for laptops (December 2021) ๐Ÿšฉ

Once you are familiar with the characteristics of a laptop power bank, we present the best models available on the market taking into account the different types of output ports: DC, AC and USB-C PD.

Notice: Remember that if your laptop has a DC charging port and you choose to buy a power bank with USB-C PD port you need to use a USB-C PD to DC adapter.

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