Anker PowerCore II Slim 10000 Ultra Slim Power Bank, Upgraded PowerIQ 2.0 (up to 18W Output), Fast Charge for iPhone, Samsung Galaxy and More (Black)

UPDATE (9-12-17)I was contacted by Anker on the same day I wrote my initial two star review. Sharon, from the Customer Service Team was great. Through email communications and my testing the battery with a different cord, we resolved that it was the cord that came with the battery that had the problem and not the battery it self. Anker was willing to send a new battery if it turned out to be the battery but it wasn't. Not only did I receive a replacement cord I received one that was longer and better in their line of cords for absolutely no charge! That's what I call stellar customer satisfaction!I am happy to say that I cancelled the return of the PowerCore II Slim 10000 battery and it is a pleasure to use and has awesome power. It fits nicely in my purse and it is so light that it doesn't weigh my purse down.I would highly recommend if anyone has a problem with this battery or any other product by Anker to work with them and allow them to make it right... they will. Five stars all the way!!Thanks much,Toni****************I waited and waited for this battery to shipped from a deal of the day price in August. Received it today (9-6-17) and it is defective and doesn't work. I own three Anker cell phone stands and one Anker portable battery so I was very disappointed when out of the box this battery would not charge. All it did was blink on the first light all day long. I switched to a couple of adapters and different sockets in my home to no avail. I received a dud and back it goes. Could the deal of the day price be associated with receiving a defective product? I sure hope not, but a number of people have complained about this battery in the reviews so I'll continue to use the Anker 5200 Mah I currently use. It's perfect, charges quickly, light weight and I've never had a problem with it.

Anker is an excellent brand for chargers, batteries, and accessories. So I trust I am getting quality components and can focus on specs. It is really nice that they keep coming with the latest fast charging technology (PowerIQ 2.0) and up to 18W output that will far exceed most phones (at least as of 2019). And it is all packed into a sleek little device shaped small and flat enough to go anywhere. This has 10,000 mAh capacity, which is a lot, considering an iPhone 11 has 3,110 mAh (and others range 1800-4000 with most being 3100 or less). I like that it is easy to check the battery level status too. And the button doesn't seem prone to getting accidentally turned on. It comes with a nice little pouch to carry it, its recharging cable, and any of your short phone charging cables to connect to it. This is one of the most optimal and worry-free balance of form, capacity, and weight in ordinary circumstances.BATTERY CAPACITY = WEIGHTYou can put it in different shapes, but it still all weighs the same proportionally to the battery capacity (in mAh). So you really have to decide how much battery backup capacity do you want versus how much weight to you want to carry around? I have a little lightweight 1,000 mAh battery stick that seems to weigh nothing, and will give you some emergency power, but far from refueling your phone. This 10,000 mAh could refuel the same phone 3 times or more. And I have a 26,800 mAh Tecnipro P26 that is a brick. Anker itself has seemingly every different possible battery capacity option out there, so too many choices may seem overwhelming. But the more you go, the more weight you'll carry. I took this to Disney World in a backpack. On its own it is perfectly fine. But as you add everything up, you end up carrying around a lot of total weight. So shaving some ounces can be good if you are going to be on your feet all day carrying it in a bag or backpack. But this one is slim enough to fit in a pocket which doesn't hurt my back or shoulders. Personally, I'd go a bit smaller for being on your feet all day carrying it in a backpack. If you aren't on your feet all day at Disney, this is a great balance of capacity, form, and weight.CAPACITYThis one hit the sweet spot for me, a lot more than my 1,000 mAh little lightweight battery stick, and fits & weighs a lot less than the 26,800 mAh Tecnicpro P26 brick that I own (good for when you want to go big or go home but not suitable for literally carrying a long time). With 10,000 mAh, it is more than you need to refuel your phone once or twice in a day. For comparison, here are the battery capacities of recent iPhones --3,969 iPhone 11 Pro Max, 3,110 iPhone 11, 3,174 iPhone XS Max, 2,942 iPhone XR, 2,716 iPhone X, 2,658 iPhone XS, 2,675 iPhone 8 Plus, 1,821 iPhone 8. This is more than an emergency reserve, but full refueling for a few in your family.

Bought this as a brute-force solution to the very aging battery in my phone, which is one of those models that's glued together and a huge pain to repair. For this it works wonderfully. Charges it many times, and easily fits in my bag and pocket, as well as stacking with the phone. The rubber side is a nice touch to prevent scratches. There is some moderate heat in the area where the circuit is while charging or discharging, but nothing unexpected or worrying.I tested the capacity with my load tester, and it is as advertised based on efficiency numbers, giving me 6.5Ah of capacity with a constant 1.6A power draw (reasonable speed to expect non-quick-charge phones to charge at). I did find that when recharging from a fully drained 0% state, if you have a quick charge power adapter you may want to re-plug it in 5-10 minutes into the charge. Since when I first plugged it in after the drain test, it would not kick into quick charging mode until it had recharged a little bit first and I unplugged it and plugged it back in. I also tested the power output with my load tester, and it was able to reach the advertised 3A number without any drop in voltage, so that checks out.Overall, would highly recommend this to people, as I would most other Anker products. Very trustworthy brand when it comes to charging equipment.