Tech Guides

5 tips on buying the correct power bank for your mobile device

By Ng Chong Seng - 3 Jun 2017

Selecting a power bank - Know your device and usage patterns first

5 tips on buying the correct power bank for your mobile device (2016 edition!)

Note: This article was first published on 3rd January 2016.

Aukey PB-N30 3,600mAh external battery pack. (Image source: Aukey.)


Because there's more to a power bank than its capacity

I’ve said this before, and I’ll say it again: while our smartphones and tablets are getting more advanced each passing day, battery tech has remained stagnant for years.

To mitigate this, device and platform makers have taken turns to come up with ways to prolong battery life, be it at the OS level (e.g., Android 6.0‘s Doze mode, iOS’ coalesced updates) or at the hardware level (e.g., Qualcomm Snapdragon 820’s ability to offload tasks from CPU to DSP). To shorten charging wait times, we also have things like Qualcomm’s Quick Charge and Oppo’s VOOC.

Still, battery life is never enough. The improvement gained from OS and SoC-level optimizations are inevitably negated as we do more on our devices. Which is why many of us who need more battery life in our super-thin smartphones turn to add-ons like power banks and battery cases.

In this article, I’m going to walk you through some considerations when buying a power bank. Some areas, like determining capacity, apply to battery cases, too. Between a power bank and a battery case, my advice is pretty straightforward: the former is great if you don’t want to bulk up your device all the time and you don’t mind carrying a small brick with you; the latter is better if you’re looking for an integrated protective case plus extra battery solution.

So here goes.


1.) Know your device’s battery capacity first

“How big a power bank do I need?” is probably the most common question I got. To answer that, you first need to know your device’s battery capacity.

Take the iPhone 6S, for example; it has a 1,715mAh battery. In a perfect world, a 1,715mAh power bank will be able to recharge the 6S fully, but we don’t live in a perfect world. Due to voltage boosting/current conversion during the charging process, some energy is lost. In my experience, real-world conversion rate of power banks can vary widely, anywhere between 60 and 75%.

So my personal rule of thumb is to get a power bank with at least 25% more capacity than my device’s battery. In the 6S’ case, at least 2,200mAh to ensure a full recharge.

Most phones will tell you their battery capacity in the spec sheet, but iPhones don't. To find out, we've to wait for teardowns from good folks like iFixit. (Image source: iFixit.)


2.) Factor in usage patterns when deciding capacity and number of ports

To follow up on the first point, I’m not saying that a small power bank or battery case is useless. It really depends on your goal.

For example, if you always end the day with 15% left on your 6S and that’s too close for comfort, Apple’s new Smart Battery Case may be all you need. Even if it can’t charge the 6S from empty to 100%, you’ll end the day comfortably with, say, 50% left.

Of course, getting a high-capacity power bank has its advantages. For one, it enables you to charge your device multiple times over. If you always forget to charge your device overnight or are always on the road and a power outlet is hard to come by, then it makes sense to get a bigger power bank. Also, bigger power banks tend to come with more than one output port, so that you can charge more than one device at the same time.

Smaller and lighter than its predecessor, the S$19 10,000mAh Mi Power Bank continues to be a crowd favorite. Click on the image to see my review on the old 10,400mAh version. (Image source: Xiaomi.)

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