Can you believe power banks mAh ratings?

A guest post collaboration by my friend, Daniel Haworth.

You'll see many battery packs (like this Blitzwolf one) listed at 10,000 milliamp hours. What does this number mean? It means that this battery is capable of providing one amp for ten hours (10 amp hours) or can also be written as 10,000 milliamp hours. Bigger numbers sound better. Often mAh is used for the marketing value instead of the Ah.

You'll often also see a smaller number labeled "watt hours" (in the case of the Blitzwolf, 37 watt hours). What's the difference between these two? Amp hours it's a measure of capacity, but ignoring voltage. A battery doesn't put out a constant voltage.

These are usually lithium batteries. It's going to go from about 4.2 volts to about 3 volts during the time it's discharging. There isn't a direct conversion between amp hours and watt hours, there isn't a mathematical conversion between watt hours and amp hours that has to be measured.

In general, when a pack says 10,000 milliamp hours it isn't really for the pack, it's for the battery inside it.

We're ignoring voltage for these tests since we're just looking at the 5-volt output. At 5 volts, we're getting maybe 70% of this number under ideal conditions. If we were looking at watt-hours we might get 80 or 90 percent of the watt-hour rating, but the amp hour rating is how the manufacturers of these have chosen to market their products.

Now, let's look at methodology: charge all of these, not super important how that's done, but they were all charged with an Ikea charger. Nothing special. Then, they were discharged by these two pieces of equipment here -- first I have this meter, USB male on one end, USB female on the other.

Once I plug in this dummy load into the meter, it will measure amp-hours. All the dummy load is doing is switching a transistor off and on to create a short. It's measuring that and doing it in a controlled way so that this appears to draw a constant current and I have it set to 1 amp out. I just let it sit and draw current until it shut off on its own, and did this for all the power banks in question.

So first we have a Blitzwolf power bank (this came from Banggood) which weighs in at 7.8 ounces and has QuickCharge 3 in and out. It also has USB-C. This is the only USB-C one that I have, but it only gave us 5,984 mAh which is 60% of the rated capacity. A little short of the ideal 70% but (spoiler alert!) they all are. So, overall, it's not too bad; a very nice, very rugged power bank that's nicely built.

The second power bank in question is the Aukey, which unlike the Blitzwolf model also has a power button you need to press to turn it on. We have QuickCharge 3 in and out and a standard micro USB connector for charging. This guy is rated 10,050 mAh, and it came with this nice bag micro USB cable.

It also feels solid and nicely built. This came directly from AUKEY as a warranty replacement for a different power bank. AUKEY definitely stands behind their products, and is concerned about customer satisfaction. You can buy these on Amazon.

The AUKEY weighs 7.4 ounces, and it came in at 6,520 milliamp hours, which is 65% of its rating. It's ever so slightly lighter than the BlitzWolf, maybe just a hair smaller and even with that has a somewhat higher power rating. I have no problem recommending either of these and next on the list.

Next is an older Anker power bank which was purchased in 2015, which comes with a microUSB cable and a nice pouch. You have micro USB inputs and no QuickCharge. This is just an intelligent two amp detecting output, so it'll try to charge your device as quickly as it can even without QuickCharge. This is a fairly large power bank that's rated at 10,400 mAh hours and admittedly this power bank is a little bit abused as is evidenced by its physical condition.

It's been through a lot, and it's getting to be fairly old. So take that into account when I tell you this number because it only clocked in at 4519 mAh hours. That's only 43 percent of its rating, and this weighs 8.6 ounces. Which is heavy considering its plastic. If you're in the market for a new battery pack, you definitely want QuickCharge.

Next, we have an Antec lifebar. The lifebar is slim, and we have a 1 amp output and a 2 amp output. There's no difference between these electrically. The only difference between them is how they identify to the device; since this isn't using an intelligent identification chip like the other ones are. This is just an older style of detection by telling the device what kind of charger it is.

An Android phone will actually charge faster off the 1 amp output. Again, it has microUSB in for charging. It also has a battery indicator light. Overall this is a really thin, lightweight thing that's rated at 3600 milliamp hours, and it gave us 2,254 mAh which is 63 percent of its rating. Not too bad!

Then our final Powerbank is an odd one: the Fuelrod. This comes from Fuelrod vending machines you might see in an airport or amusement park. The whole deal with this is you can deposit this back in the vending machine and the vending machine will give you a new fully charged one. It's an interesting idea, but very tiny. The Fuelrod is only rated for 2600 milliamp hours; I got 1930 out of it which is 74% of its rated capacity. But, there's a caveat here. The electronics in this are not nearly as good as the other power banks.

When I plug in the meter it goes to 5.1 volts, that's reasonable enough. But, as soon as I plug in our load we go down to 3.9 volts now that this power bank is about 20% charged. So this is way under voltage. It did give us that high milliamp hours reading but because we're ignoring voltage that's not telling us that this actually isn't putting out a usable amount of power. Your phone will not charge properly from this so that's not good. It's actually a waste of time and money, so don't buy these. In fact, don't buy strange power banks from vending machines in general!

Anyway, that's all for now. Have a wonderful day!