Power-Bank-Portable-Charger - 40000mAh Power Bank QC 4.0 and PD 30W Quick Charging Built-in LED Display 2 USB 1Type-C Output Compatible with Most Electronic Devices on The Market(Dull Black)

Assuming a valid computation of the power bank's capacity based on how long it takes to charge some device is erroneous. Different power banks have different charging circuits which can substantially invalidate the computation. And for using discharge-time to calculate how much power bank capacity is used to charge a phone, different power banks may vary many10s-of-millivolts, which will vary the time to charge the phone enough to make this assumption invalid.A better way to test a power bank's capacity is to get a "USB tester." They're surprisingly inexpensive, and they all have accurate calculators that display how much charge(mA-hrs) is delivered to a device (or power bank) under charge, including the total capacity when charge is completed. It occurs to me that it would be accurate to tally up the milliamp-hours going into a phone's battery by turning off the phone while it's charging, so the tester will only be tallying up battery-capacity, without the phone using up any charging current. Of course, for measuring the capacity of a power bank, you don't have to worry about charge going anyplace besides the battery.If you want to determine the total capacity of, let's say, a power bank, Step 1 is to discharge the power bank all the way. Discharging the power bank completely is not a nice thing to do to its lithium battery, so I try not to do that test, myself. But if I ever do the test, I'll update here with a result.In practice, I like keeping one of these monster power banks near my seat, if I don't have an AC USB charger nearby. And I like the bank's small digital display of remaining percentage to tell me that the power bank needs to be recharged before it gets over-discharged. And, just to make trouble, if the percentage readout were off by a few percent, the display is still sufficient to help avoid over-discharging the power bank so if achieves long life (and prospers). Instructions say to recharge the power bank before it drops below 25%. I would add "... if you have the chance."To treat my cellphone batteries most gently, I like to charge them most slowly (if I'm not going anywhere, such as during bedtime). A USB tester will tell you if a quick-charge method is increasing the charge-voltage above 5 volts, which may be quicker, but that's not the healthiest way, generating heat inside the battery, etc. I must remember that the power bank's USB-C jack is not only an input for charging the power bank, but it also can be used as an output to charge a device, for a total of 3 outputs from this power bank(!). I'll have to get my USB tester to confirm the USB-C jack is a plain, no-quick-charge output.

I just want say this charger is top notch. This portable charging bank is reliable and a convenient solution for powering devices on the go. It features a high-capacity battery that can charge a smartphone multiple times, making it ideal for travel or busy days. I keep it on the go for work. The compact design fits easily into bags or pockets, while multiple USB ports allow for charging several devices at once. Fast charging capabilities, LED battery percentage is a nice touch. The flashlight is a nice touch for added accessibility. Durable and efficient, it’s a must-have accessory for anyone who relies heavily on mobile devices.

It was at the bottom of a drawer, among old cables and manuals for things I no longer own. Black. Unbranded. I don’t remember buying it. I’m not even sure it’s mine.I slipped it into my bag without thinking. I didn’t use it during the trip. Outlets were everywhere. Nothing seemed to justify its presence. But I didn’t take it out.One night, in a room with curtains that didn’t fully close, I woke up without reason. Outside, a streetlight filtered in like a thought that refuses to leave. I turned on my phone. Everything was fine. Still, I plugged it in.It lit up. A small point of light. I couldn’t tell you what color. I watched it for a few seconds, then unplugged it and went back to sleep.Since then, I always carry it with me.Not because it’s useful.But because that night, something —tiny, quiet— felt aligned.And sometimes, that’s enough.

Seems heavy to use for travel. Takes a long time to charge. Built for durability. Bright flashlight.

This is easily one of the best portable chargers I’ve ever purchased. It can recharge an iPhone multiple times and has never let us down. One of the most impressive things is how long it holds a charge. I put it away for the winter and when summer rolled around, it still had 100% battery after months of sitting unused.It also recharges quickly, so you can top it off right before a trip and be confident it’s ready to go. It’s not too bulky either and feels solid and comfortable to carry around.