Bests & Worsts Reviews from Amazon

I'll start with the meat. My trials tested this and ran at an average of 13,709 mAh, which sounds low, but it's actually right on the mark to meet the claim of 20,000 mAh. Here's how. That's 13,709 mAh that I got out of the pack at 5v, not how much went into charging it, so this is real usable capacity. We can work backwards to find what's in the pack. (I rounded to whole numbers in the below figures, and these figures were obtained using a 1 A load) 13709mAh * 5v = 68545 mW 68545mW / 3.7v = 18525 mAh at 3.7v 18525 / 0.90 = 20,584 mAh actual battery pack capacity at 3.7v after factoring in 10% loss for the regulator I tested this with both real devices and variable load modules. My phone, PS Vita, and an old MP3 player seemed to top out at draining from this thing at about 1 A. I'm guessing that must have been a limitation of the devices that I attached to the power bank because I also tried the variable load module, and was able to pull 2.8 A off it for some time, which is above the 2.4 A stated limit. I did this for about 5 minutes and noticed the device did get warm, but not dangerously so. I conducted the rest of my tests by setting the variable load to 1 A and 2 A. It seemed to hold up slightly better at 1 A than 2 A, as expected. It was cool while at the lower drain rate and I seemed to get about 2000 mA more out of the pack at 1 A than at 2 A. Not earth shattering, but something to keep in mind. The pack itself is relatively heavy, which is good for something like this. Light means it's light on lithium, and a 20,000 mAh pack shouldn't be. The LED lamp on it is a bonus and functions well enough to get around a dark room, and will stay on for a very long time if that's all you're using the pack for. I left it on for 5 hours, and it didn't go down 1 notch (out of 5) during that time. The dual inputs for faster charging is actually an asset here. I had it hooked up to two 2.4 A ports on a USB charger, and it actually charged in not quite half the time. 6 hours compared to 10. Still, a welcome improvement with a large pack like this. If there are concerns about charging this too fast and reducing cell life, I wouldn't worry about that. There must be at least 8 cells in this, which would put the per-cell capacity at around 2500 mAh. A 1C (2.5 A here) charge rate would be a quick charge and 0.5C (1.25 A here) would be a standard charge. Having both inputs active at full capacity would yield a max charge input of 4 A, spread over 8 cells is about 0.5 A, or about 0.20 C, so it's not a dangerous or damaging charge rate. Overall, I would say that this was a good buy. I purchased two of them, and I'm adding it to my "save for later" list in case I need a third. EDIT: July 3, 2017 NOTE: Opening a device like this should only be performed by a professional, and using appropriate tools and safety precautions. Shorting a power pack like this can cause a fire, so don't do this at home unless you know what you're doing. Additionally, keep in mind that doing so voids the warranty. I've also been asked by the manufacturer to censor the model number of the cells to protect their intellectual property. I have circled another part that is of interest, the rating of the cell from the manufacturer, so these are genuine cells. I performed an additional drain test to see how far this bank can be pushed. I don't recommend pushing it beyond the rated 2.4A @5v, but my particular unit was able to keep its voltage statistically stable at 2.6A out of one port. After performing a teardown of the device, I found that my math was right. Inside are 8x 2600 mAh 3.7v cells, for a total of 20,800 mAh. Looks like we get what we're paying for. That being said, at a purchase price of $30, that's less than $4 per cell if you want to scrap this and use the cells for projects. Good value either way!