Review – Is MAXOAK 50,000mAh the best external battery?

MAXOAK external battery

Is this the best external battery for laptops and phones?

According to their ads, they claim this battery can store 50,000mAh or 185Wh (their own calculation). They also claim this battery can charge any devices that can pull up to 90W.

That’s good, since even the Core i7 version of Surface Pro only ships with a 44W power supply.

So how does this battery perform?

(Note: This review has been tested using the Core i7 version of the Surface Pro)

Packaging & Dimension

So what’s in the package? The package contains the battery, the charger for the battery, a case, and bunch of connectors for charging different laptops.

Please note that the MAXOAK does NOT come with a charging cable/connector that is compatible with the Surface Pro’s charging port! You must buy a cable such as this – this cable works for me, and it should work for you as well. The price for this cable is reasonable, and it is magnetic.

Here’s how the case looks:

The material is soft, cushy, and feels nice but don’t expect it to protect against strong impacts. Protection against small bumps and scratches should be fine.


Here are ALL the ports available on MAXOAK. No other ports are present in other sides of this device so what you see here is all you get.

The MAXOAK features:

  • one 20v port for charging laptops (with appropriate cables/connectors)
  • one 12v port – I can’t think of anything to charge using this port, but perhaps with the right adapter, common 12v automobile accessories can be used. Perhaps during camping?
  • two 2.1A USB ports for charging phones & tablets
  • two 1A USB ports for charging phones
  • one “in” port for charging the MAXOAK battery

Theoretical numbers

Firstly, let’s look at their claimed 185Wh number.

Internally, rechargeable batteries operate in 3.7v. Hence if you convert 50,000mAh at 3.7v, then the number does add up to exactly 185Wh. Given that the Surface Pro uses approx. 45Wh batteries (please read this article), this battery should allow FOUR full charges.

Not bad? Let’s see if it performs anywhere near this manufacturer claimed number.


Before starting the test, I made sure that the laptop battery is drained down to 19%. I tend to panic and start looking for power sources seriously when I hit 20%. Conveniently, the Surface Pro, in its default setting, also gives low battery warning at this level.

The Surface Pro is left in sleep mode, rather than fully shut down.

I also made sure that the MAXOAK battery is fully charged.

Remember to press the MAXOAK’s power button once after connecting the cables to start the charge, otherwise it will behave as if the battery is dead.

Charging Surface Pro

In this test, I am measuring the time it takes to fully charge the laptop. Obviously, this depends on how much current the battery can provide through the charge port.

Two numbers should interest the readers – total charging time, and how much battery charge is remaining in the MAXOAK battery. Since the built-in indicator for figuring out the amount of charge remaining in the MAXOAK is rather rudimentary (4 tiny LED lights), total number of full-charges might prove to be a more interesting number.

Here’s the rate at which the laptop gets charged when fed by the MAXOAK battery, The Surface Pro started the charging process at 19% in this round and stopped at 97%.

Charge Time Surface Pro Battery Level
0 mins 19%
10 mins 25%
20 mins 32%
30 mins 40%
40 mins 48%
50 mins 55%
60 mins 64%
70 mins 71%
80 mins 78%
90 mins 86%
100 mins 91%
110 mins 94%
120 mins 96%
130 mins 97%

As you can see here, the charge rate stays fairly linear then tails off near the end. This is typical for all charging devices.

At no point during the test did MAXOAK get hot. In fact, it didn’t even become warm to touch – the metallic case felt rather cool throughout.

At the end of this test, one of the four LED lights was off. It went off at 80min mark. Does this mean it has used up 25% of the battery charging only 70% of the Surface Pro battery? Does this mean this battery can “only” provide 2.8 full charges?

In reality, all rechargeable batteries can only provide around 75-80% of its theoretical maximum values. If the MAXOAK can provide 3 full charges, that would be a decent showing.

At around 2 hour mark, for some reason, the MAXOAK stopped feeding charge to the Surface Pro. I had to click on the power button to resume charging. The charge level was at 97%. But few minutes later, the charge gets disrupted again. Perhaps the Surface Pro is drawing such a low level of current that the MAXOAK thinks the charge is complete.

In summary, MAXOAK is capable of charging from 19% to 91% in 1 hour 20 mins. MAXOAK is not capable of charging beyond 97%. Still, these numbers are very promising for those who travel frequently.

Now, continue on with more full charge rounds to determine the total number of full charges.

Charge Round % Battery Charged
1 77%
2 80%
3 80%
4 58%
Total % Charged  295%

During this test, I’ve managed to get 295% charge over 4 runs. This is pretty close to my expectation, so I’m happy with this results.

Charging MAXOAK battery

In this test, I am measuring the time it takes to charge the MAXOAK battery itself. Obviously, the laptop is NOT connected during this test.

The power supply of the MAXOAK is rated at around 40w. My expectation is that it will complete charging in about 6 – 7 hours.

Once again, I detected no sign of overheating – the case remained cool to touch throughout during this test.

At the end, it took exactly 7 hours to fully charge the MAXOAK – a slightly disappointing result.


Overall, I am very satisfied with the performance of the MAXOAK battery. It charges a Surface Pro laptop in under 2 hours. I believe this is currently the best option for those needing multiple charges without spending a fortune.

A room for a small improvement – perhaps a more powerful power supply would have been nice. There’s no sign of overheating at all, so perhaps there is a room to improve this without significantly boosting the overall cost. 7 hours of charging time during the day is somewhat long, especially if you are travelling.

Oh and if you intend to get the MAXOAK, PLEASE make sure that you also order this cable! You can’t charge without this!

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Kent Beck

Kent Beck link to his wiki

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