Friday, January 16, 2015

Information about Power Bank Portable Chargers

A lot of people have problems with keeping their mobile devices charged.  Tablets aren't too bad, unless they're playing a lot of video or streaming data.  Mobile phones can drain really quickly, especially if they're being used in remote regions or inside buildings, where mobile coverage is cutting in and out frequently.

The simple solution is to always keep a wired charger handy so you can plug into the nearest wall outlet.  But what if there are no outlets around?  This can happen frequently, for example:
- Hiking, or camping in remote areas.
- At sports event.
- In some bars or restaurants.
- At some airports or train stations.

Those are just a few examples.  The simple solution is to buy a "power bank."  A power bank is essentially a portable battery, which you can use to re-charge your mobile device.

A power bank will generally charge devices that can be charged over things like USB cables, but can't charge items that plug into a household outlet.  So for example, you can usually charge tablets, phones, mp3 players, and some GPS units.  You can also charge a small number of cameras, such as GoPro cameras.  Some tablets, most cameras, and laptops require a wall plug, so a power bank isn't going to be helpful for these pieces of equipment.

On that topic, let's look at some specs.  Most items that are 5 volt can be charged by a power bank, not specifically because of the voltage, but just because devices with 5v usually have the proper charging connections that can be taken advantage of.  Some tablets and many cameras range from 8 volt to 12 volt, and can't necessarily be charged.  Laptop computers generally accept between 12 volts and 24 volts.  The charger on the laptop is actually a step-down transformer to convert 110/120v or 220/240v into the proper voltage for the laptop.

Power Banks are essentially batteries.  You charge them, then they hold this charge until you drain it by moving it into another device.  In fact, you can say that a power bank IS a battery, technically speaking.  In fact, the innards of a power bank sometimes are one big battery, or a bunch of smaller batteries connected to each other.  There is a small portable battery called an 18650 that is commonly used in Asia to provide the storage capacity inside a power bank.  A couple or several 18650's are wired together inside the power bank, depending on the size and capacity of the power bank.  By the way, this isn't necessarily a good thing, as we'll find out in a minute.

The guts of a power bank are usually lithium ion or lithium polymer storage.  Lithium ion is a liquid electrolyte.  Lithium polymer is a solid polymer electrolyte.  What's the difference?  Lithium polymer, or LiPolymer, is generally better.  It can have a flexible size and dimension.  It producers less heat, which means that it's more efficient and safer.  It has a lower self-discharge rate.  The storage capacity decays more slowly.  The only real drawback about using LiPolymer instead of Lithium Ion is that LiPolymer is more expensive.  That's the reason Lithium Ion batteries (18650's) are less desirable.  You may find that some no-name power banks are just a bunch of old 18650's that have been recycled, not necessarily even fresh new batteries!

The health of your phone battery decays over time.  That's why a new phone can generally hold a charge longer than when the phone starts to get older.  You could say that if a phone's battery health is at 80%, its charge can only last 80% as long as it would have when the battery was new.

As you're moving energy around from item to item, some of it is lost either as heat or due to inefficiencies in the conversion process.  This is important when figuring out how much a power bank can help you.  We'll get into that in a minute.

Here are some of the specs that you should look for in a good power bank:

- What is the number of mAH?  This stands for milliamp hours.  Ideally it should be at a voltage of five volts.

- Can the power bank charge and discharge simultaneously? It could be frustrating to have a power bank that will not charge another device while it is itself charging.  Some power banks will both charge internally and charge an attached device if the power bank is itself plugged in and charging.  Other power banks won't charge the attached device until the power bank itself is unplugged from the wall.  And finally, some power banks, if plugged in and attached to a device that they are charging, will let the power from the outlet pass through and charge that remote device first, before the power bank itself starts to charge up.

- How many output ports are there?  Can two devices be charged simultaneously?

- What is the output current rating?  A higher number is generally better.

Your biggest question when looking for a power bank is probably something along the lines of, "How many times will it charge my phone?"  Is there a simple way to figure this out?  Well, sort of.  But the formula isn't perfectly simple.

Some power banks have very low capacities, with rated capacities listed as probably under 4000 mAH.  These are no good.  They probably have one or two 18650's inside them, and might barely provide a single charge for a typical phone.

Some power banks have very high listed capacities, like 40,000 mAH and higher.  It seems that a lot of these are actually scams.  There are some that are legitimate, but a power bank would generally have to be fairly large to have that capacity, not the sort of thing that would be the size of a deck of cards, and convenient to carry around.

Other power banks have capacities of perhaps 8,000 to 15,000 mAH.  In my limited experience, these tend to be the best ones.  They're probably a branded model, and the numbers are more likely to be accurate.  You best bet, however, is to double-check by doing a google search for reviews on the exact brand and model of the power bank you're looking at.  Luckily, a lot of people who have bad experiences with a particular purchase will post the info on the internet, which can prevent other people from being ripped off.

Some power banks have internet circuit protection.  This is important.  If you have something without circuit protection and it gets connected to the wrong thing, it's pretty easy to hurt the internal batteries so they die or become extremely weak.

Let's say that you have a phone that has a 3,000 mAH battery.  Let's also say that you have a Power Bank that stores 12,000 mAH.  You've probably already come up with a very good question … can you just divide these numbers to come up with the amount of times that your phone can be charged by the power bank?  In other words, can your power bank charge your phone exactly four times?

This is good logic.  It's also moderately correct.  The only problem is that you have to factor in the phone's battery heat, and the conversion rate.

Let's say that your phone is getting older and it's only about 80% healthy.  The problem is that there's no exact scientific way to measure this for the average consumer, so it's a guess.  You can probably figure it out roughly from experience after charging your device several times.

Also, let's say that 15% of the stored energy is lost in conversion.  That means that only 85% of the stored energy in the power bank will make it to the battery of the device being charged.

After considering these two adjustments, the correct formula for figuring out roughly how much your power bank will charge would be:

Storage of Power Bank * Conversion Rate * Phone Battery Health / Phone Battery Capacity

Or in this example:   12,000 * 0.85 * 0.80 / 3,000 = about 2.72 times.  Nearly three full charges.

As I said, this is a rough equation, but by guessing the approximate phone battery health and conversion rate to temper your expectations, you're going to get a more accurate assessment than by using impossible "perfect case" results.

A lot of the cheap no-name power banks made in Asia are sketchy.  Many are cheap and use old recycled batteries.  A new 18650 is supposed to have a charge cycle of 300 charges before it's essentially useless.  However, if an unscrupulous vendor builds a bunch of power banks with old used 18650's, you might not get very many charges out of it before it dies.  Also, there have been occasional cases of someone buying what feels like a hefty power bank that must have quite a bit of storage capacity, and it's only got one or two 18650's and a bag of sand to tricky people.  Try to look for something that appears to have a brand name, at the very least!  And look for detailed specs.  The specs may be a lie, but if they're detailed and look legitimate, there's maybe a slightly better chance that you're getting a product that isn't a sham.

I did a short video to show you a power bank that I purchased.  I got lucky, this one turned out well.  I don’t think it's in production anymore because it's been replaced by a 13,000 mAH model, but the exact specs of mine are as follows:

- IntoCircuit Power Castle Series
- Model PC11200
- 11,200 mAH, 5 volt
- Can charge two devices simultaneously
- Has internal protection for under/over current/voltage
- Does not come with a charger, must use the charger for your phone or other device
- Only cost about $30 Canadian plus shipping from Amazon

Like I said, it's worked decently for me.  I did some tests on recharging my Nexus 5, which has a 2300 mAH battery.  Starting with the power bank at 100% and the phone at 0%, it took 108 minutes to charge using the 2.1amp line, which drained the power bank to 63% of its charge.  Using the 1.0amp line, it took 137 minutes to charge the phone, but it only drained the power pack to 83%.  I'm optimistic that by using the lower amperage line, I could probably get at least four and maybe almost five full charges out of the power bank, if it hasn't been sitting around for too long (your power bank, like any battery, will slowly lose its residual charge if it sits for an extremely extended time period).

Here's the video about my own power bank:

One last important consideration is that most airlines do NOT allow you to have power banks or other significant amounts of batteries in checked baggage, unless they are actually in a device!  So a battery inside a camera inside your luggage is fine, but a spare battery is not.  Therefore, remember that you will be forced to carry your power bank as a carry-on item!  Also, many airlines have regulations on the number and capacity of batteries that you can carry.  This probably won't be an issue, because it's a pretty generous allowance.  For example, several airlines won't let you have batteries over 160 aH (160,000 mAH).  But this is the size of a truck battery.  Many airlines also have rules like "maximum of ten lithium batteries per person in your carry-on, and any lithium batteries in checked baggage must either be installed in a device, in the original packaging, or in a carrying device that insulates the battery terminals."  Check the rules in advance for your particular airline if you're going to fly somewhere!

I'll wrap this up with a list of the battery capacities for a number of phones that are commonly available today.  I'm sure this list will be quite out-of-date within 24 months, but at least it'll give you a general idea of typical battery capacities:

1810 mAH – iPhone 6
2915 mAH – iPhone 6 plus
3220 mAH – Samsung Galaxy Note 4
2800 mAH – Samsung Galaxy S5
3100 mAH – Sony Eperia Z3
3900 mAH – Motorola Droid Turbo
3000 mAH – LG G3
2600 mAH – HTC One M8
2420 mAH – Nokia Lumia Icon
2400 mAH – Amazon Fire Phone
2300 mAH – Google Nexus 5
2100 mAH – Blackberry Q10
1800 mAH – HTC Windows Phone 8X

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