Best Battery Banks on Amazon

With cell phone batteries struggling to get through a full day of use, these great little devices are an essential item for everyone. They can get you out of sticky situations or if you buy a larger one then they can keep you going for a week-long camping trip off the grid.

Which Capacity

So you have a 4000mAh battery so a 4000mAh battery should give you a full charge right?… Wrong!.

We will go into why this is the case later in this article but the general rule of thumb is that you are going to get roughly 2/3 of the capacity from a battery bank.

This isn’t because you are being conned. The battery in the power bank is indeed going to be what it is rated at (at least the ones on this list!), but there are energy losses with energy conversions and losses due to heat and other factors.

The capacity you choose is also going to come down to what your needs actually are. Do you just need a small battery bank to get you through the day or do you need a beastly powerhouse to get you through your next camping trip… Why not both?

Generally, if you want a portable power bank to give you a little extra juice or as a backup, then you will be looking to get one of the cylindrical battery banks which will be around 3000-5000mAh.

If you want something a little more capable to chuck in a hand bag or a backpack then you will be looking for a battery bank with around 10,000mAh to 20,000mAh. Keeping in mind you will be looking to get around 3 full charges on a 10,000mAh battery and around 6 charges on a 20,000mAh battery for an average cell phone.

Best Ultra Portable Battery Bank – Anker 3350mAh Power Core

Anker is probably the most well-known brand of battery bank and for a good reason. They use genuine batteries in their banks instead of cheap Chinese batteries which can have overstated capacities and will show signs of degradation faster.

This Anker power bank also contains fast charging which is rarer on these lower capacity power banks.


You should expect to get around 70% charge from this little 3350mAh power bank, which is ideal for something that you will keep in your pocket.

Build Quality

This is a solid little device which is designed to be thrown around a bit. There is no flex in the casing and you would really have to try to break it.

The Anker Power Core is the only battery on this list with an Aluminium outer casing which makes it feel like a quality device that is built to last.

Who Should Buy It

This battery bank is ideal for emergencies or just giving you that little bit extra juice to get you through the day. It is the perfect size to keep in your pocket.

Best Portable Battery Bank – Poweradd Slim2 5000mAh

The Poweradd Slim2 battery bank is a great bang for buck and actually comes in cheaper than the smaller Anker battery while offering a similar level of quality, minus the aluminum construction.


This 5000mAh power bank should be able to give a full charge to a lot of phones or at least get very close to it.

Build Quality

The Poweradd Slim2 has great build quality which is better than a lot of equivalent batteries at twice the price.

Just like all the batteries on this list, Poweradd uses quality components and branded batteries internally.

Who Should Buy It

The Poweradd is a little chunkier than the Anker 3350mAh battery which may be a little much to keep in your pocket but would be ideal in a bag. It’s still ultra-portable though and will significantly extend your phone’s battery.

Best 10000mAh Battery Bank – Wofalo Wireless Battery

This power bank from Wofalo has wireless charging built in which is rare to see on a battery bank. This means that you can stick it on your desk and you can just plop your phone down on top of it and your phone will start charging… Providing your power bank has wireless charging built in.

The Wofalo also comes with a built in cable which tucks away when not in use and comes with a handy little converter for iPhone users.


At 10,000mAh you can expect to get around 2 full charges for an average cell phone and you are starting to get into the range where you will get a full charge for a small tablet.

Build Quality

Build quality is solid on this battery bank. This is where you start to notice some batteries having lower build quality, because they will flex and creak if cheaper plastics are used. None of which this power bank does though and everything feels solid and well built.

Who Should Buy It

This is perfect for people who work desk jobs and need a power bank to sit on their desk while at work so they can stick their phone down and wireless charge without having to worry about wires.

It is also the perfect size to keep in a bag since its still thin and lightweight.

Best 20000mAh Battery Bank – iMuto 20000mAh

iMuto have a great range of batteries and they are all great quality. But this one takes our best 20,000mAh spot because it is a solid device which offers the best bang for buck.

The iMuto battery comes with a handy display to show you exactly how much power you have left, which is much better than having a few dots to guestimate how much is left.


With 20,000mAh you should be expecting in the region of 4-6 full phone charges which is enough to get you through a weekend away charging 2-3 phones.

Build Quality

Build quality on the iMuto devices is second to none, especially in this size when most other brands start to display some flexing which show up the cheaper materials. This battery bank is solid though and feels built to last.

The batteries used inside are also branded batteries which will give you the same level of longevity you would expect from more expensive brands like Anker.

Who Should Buy It

This battery has a little more heft to it but will feel at home in a backpack. This battery is ideal for longer trips away or for anyone who isnt always going to be near any power for a few days.

Best Wireless 20000mAh Battery Bank – KUPPET 20000mAh

So for a little more money than the iMuto device you can pick up a slightly more portable wireless charger which will allow you to ditch your wires and just stick your phone on top of the battery bank.

Just like the iMuto, this device comes with a percentage display so you know exactly how much battery you have left.


Capacity is going to be roughly on par with the iMuto device so you should expect to get 4-6 full charges of your cell phone and around 2 full charges of a tablet.

Build Quality

Build quality again is fantastic, it does have a little bit of a more plasticy feel but still maintains a solid feel and looks great.

Who Should Buy It

This is a little more expensive than the iMuto device but will suit someone with a device which supports wireless charging. This is ideal for office workers or just chucking in a backpack.

Best 30000mAh Battery Bank – iMuto 30000mAh

So you need massive amounts of power? This 30,000mAh power bank from iMuto is going to give enough power to keep you going for a long time off the grid and if you go for the upgraded usb-c version then this will have enough amperage to charge some newer laptops which will charge over usb-c.


You should expect 7-8 charges for an average phone and around 3 charges for tablets at this capacity (depending on the size of the tablet).

Build Quality

This is the bigger brother to the 20,000mAh iMuto battery which is also great quality. Almost all other batteries we tested at this size were starting to show signs of lower quality plastic, but this iMuto felt just as solid as it’s smaller 20,000mAh brother which is impressive given it’s size.

Who Should Buy It

This one is going to be a little bit on the heavy side to keep with you on a daily basis. This is the ideal battery for someone going off the grid though and paired with a portable solar panel this will be able to provide infinite power off the grid!

Best 50000mAh Battery Bank – Maxoak Laptop Battery Bank

This is a different beast when compared to your average phone power bank because it provides up to 20V/3A which is enough to charge most laptops. This capability comes at a price, but if you need a battery bank which can power more than just your cell phone then this is going to be your best bang for buck.


This has enough capacity to charge your phone up to 15 times roughly (depending on the phone). This will be overkill for most people though unless you live 100% off the grid.

Where this capacity comes into its own though is when you are charging larger devices such as laptops and tablets.

Most new laptops have somewhere in the region of 50Wh batteries and this battery bank has a 185Wh capacity, meaning that you can expect to charge an average laptop around 3 times. This will vary greatly with different laptops but with newer laptops having all day batteries this means you can extend your capacity to multiple days and if you were to pair this battery bank with a portable solar panel, then you could have infinite power off the grid.

Build Quality

We wouldn’t put something on this list that was built cheaply and this device is no different. This is a hefty device which comes with a high quality outer casing and uses high quality components inside.

The batteries are also branded batteries instead of the cheap chinese knock offs which means it should last for thousands of charge cycles.

Who Should Buy It

This certainly isnt a daily carry item and will be more suited to someone who is traveling in a campervan or likes to go camping and still have power for all their devices.

Paired with a portable solar panel this device will keep you going indefinitely, which really opens up a lot of opportunities for where you can go without power.

Battery Bank Efficiency

So just why don’t you get 100% efficiency from a battery bank?

Energy Conversions

The main area for loss is due to the difference in output voltage when compared to the battery voltage.

Battery banks typically have a voltage of 3.7 volts, but USB uses 5 volts. This means that the voltage needs to be converted from 3.7 volts up to 5 volts which means a 23% loss right off the bat.

This means a typical 10,000mAh battery is instantly dropped to 7400mAh right off the bat.


Converting energy always results in at least some form of waste energy and in this case we get waste energy in the form of heat.

Typically you can expect to lose between 2-10% of your charging capacity to heat losses which will drop your 10,000mAh battery even further to around 7000mAh.


It would be nice if manufacturers made this more apparent that 10,000mAh in their battery doesn’t equal 10,000mAh in actual charging capacity. Some will state that you should take 25-30% off for losses but not all make this apparent to the consumer.

It would be more accurate to rate power banks and batteries in general with watt hours because it is a more accurate figure to use. But for some reason, watt hours is generally only used for larger capacity batteries on laptops and other larger devices.

All manufacturers do this though and all suffer from the same losses. Your best bet is to just calculate the actual capacity as 2/3 of the stated mAh and make sure you get a battery bank which uses quality branded batteries internally.


Leave a Reply

Your email address will not be published. Required fields are marked *