Review: Alpatronix Galaxy S9 4,000mAh Battery Case

Alpatronix Galaxy S9 4,000mAh Battery Case











  • Has enough power capacity for at least one full charge
  • The battery case is able to recharge with a wireless charger and through its USB-C input
  • You can sync and charge your S9 without having to take the case off


  • Provides only partial protection to the front of your S9
(Last Updated On: July 31, 2018)

When it comes to purchasing a battery case, it’s best to know what the case is like before you actually jump to purchase one. The reason for that is because there are so many of them on the market, as people find value with battery cases as they’re basically portable chargers that come in the form factor of a case. Another thing to consider is just how much power capacity the battery case features and the user experience that you’re going to get from it.

In this review, we’re going to be taking a look at this Alpatronix Galaxy S9 4,000mAh battery case. Alpatronix is quite well-known brand when it comes to battery cases, so let’s see if this is one you should be getting for your S9.


Power Capacity:

The power capacity of this S9 battery case is 4,000mAh and this might sound like a lot, and even though it’s a good amount, it’s not the real power capacity that you’ll actually receive. Just like portable chargers, the power capacity of a battery also goes through a conversion of power, and so, once the power has been converted, is how we figure out how much power you’re really able to use towards charging your S9.

3.7 x 4,000 = 14,800 / 5 = 2,960

So the actual amount of power capacity that you’re able to use from this charger is going to be about 3,000mAh. This is the average conversion rate and it’s with this much power that you can basically get an additional full charge for the S9, as the Galaxy S9 has a 3,000mAh battery capacity.

Output Charging:

The charging speed of most battery cases is going to be quite slow for the S9 and basically battery cases, in general, have a slow charging speed for the smartphone that they’re made for. That said, the charging speed for the S9 from the battery case is 5V/1.8A and even though this isn’t Quick Charge speeds, it’s an alright standard charging speed that’s quite close to 2 Amps.

So, no. This battery case will not fast charge your S9 but it will at least keep up with the power consumption that the S9 has and so it’ll charge while you use the S9. At the same time, the more you use your smartphone then the less the power capacity will be able to provide a full charge because there’s power being used. Just something to know.

Also, this battery case does not feature Priority fast charging, meaning that even if you use a Quick Charge wall charger to recharge this battery case, it will not fast charge your S9. Instead, the battery case will just be recharged and the case will regularly charge your phone.

Input Charging:

To recharge this battery case, there are two options. You can either use the USB-C input on the battery case which has a 5V/1.8A recharging speed. Or you can wirelessly recharge the case with a Qi wireless charging pad or stand, but that will result in a slower recharging speed of 5V/1.2A.


Size and Weight:


Of course, no matter what, a battery case is always going to be larger and heavier than just a regular case because of the batteries and circuitry that it uses. That said, for a battery case, this Alpatronix one has a rather slim form factor that might not be as much as a nuisance as you might think.

It has a length of 6.2 inches, a width of 2.8 inches and a thickness of 0.6 inches. The weight of the charger is going to add 4.1 Ounces to the S9. So you’re going to feel the thickness of the case the most likely when you place it into your pocket, but when it comes to holding it in your hands, we found that it actually provides a better grip rather than the S9’s plain and slippery feel.

Functional Components:

On the function side of things, it’s what you can expect from most other battery cases, as this one has a just two main pieces, with the top portion that comes off so you can slide your S9 in the case and there’s no other assembly needed. At the back is where the power button is used to turn on the case by holding it down and you can turn it off by doing the same thing. There are also four White power capacity indicators right next to the power button.

At the bottom is where the USB-C input port is to recharge the battery case.

The main flaw not only with this Alpatronix battery case but most other battery cases are that it can be awkward trying to use the fingerprint scanner as the case is raised so much from the phone that you’ll have to really reach for it to actually reach scanner.


Structure and Material:

The build of the case actually provides some solid protection, as the entirety of the back and sides of the S9 are safe. There is frontal protection but the raised bezels are only at the top and bottom of the phone because the screen to the sides makes it difficult to have raised bezels without sacrificing your user experience with the S9.


The charger does get a little warm if you’re charging your S9 for a long duration but other than that, there’s nothing wrong with the way it charges or recharges,


This Alpatronix battery case is what you should expect from a standard battery case for a smartphone as it has enough power capacity to charge the S9 to full power at least once and it has a form factor that might be large but not absurdly large. So doesn’t take any chances and we think that’s where it holds most of its value.

That said, if you’re searching for a higher power capacity battery case, then ZeroLemon’s S9 battery case might serve you better.



The power capacity is enough to charge the S9 to full power at least once. There are two ways to recharge the case, by using either the USB-C port or with a wireless charger.


The charger has a slim form factor for a battery case and it’s easy to place your S9 in the case because of its removal top piece.


Unlike how some battery cases don’t provide frontal protection, this case does provide some at the top and bottom of the case.


The battery case makes use of powerful charging features and an easy to use design that you’ll have no problems taking anywhere.

Specs of the Alpatronix Galaxy S9 4,000mAh Battery Case:

  • Power Capacity: 4,000mAh | Output Capacity: 2,960mAh
  • Output: 5V/1.8A
  • Input:

USB-C Input: 5V/1.8A

Wireless Input: 5V/1.2A

  • LED Power Indicator: Four White Power Indicators
  • Size: 6.2 x 2.8 x 0.6 inches
  • Weight: 4.1 Ounces


We’re reminded of why Alpatronix is quite a popular brand when it comes to battery cases, as they do everything by the book and their products, such as this S9 battery case turn out quite well.

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