The short version, it's really a 3000mAh real world battery bank advertised as a 5000mAh battery bank. The long version is as followed:

I bought one of these Anker Nano Power Bank (22.5W, Built-In USB-C Connector) model A1653 from Best Buy when my wife and I got our new Samsung Galaxy S24 Ultra because she carries a 10,000mAh Samsung battery bank in her purse that was heavy and I thought, hey, these Anker Nano power bank has 5000mAh advertised capacity, and the Samsung S24 Ultra also has 5000mAh capacity, so it should be able to charge her phone from drained to 100%, right? Wrong! The power bank will start strong, but quickly overheats and won't charge at the faster speed, I am guessing the internal protection limits the power output when it gets to a certain temp. A fully charged Anker Nano power bank will only charge her phone about 55-65% while idled, and will get really hot. And, it won't let you charge it until it cools down.

At first I thought maybe we got a defective unit, so I exchanged it at Best Buy, but the new unit does the same thing. So I reached out to Anker support, and this is what they replied:

" I'm sorry to hear that you're experiencing issues with your Anker Nano Power Bank. It's important to note that power banks typically output around 60%-70% of their advertised capacity to the connected devices. This is due to energy lost in circuit heat and voltage conversion during the charging process. Therefore, a 5000mAh power bank may only effectively provide 3000-3500mAh to your device.

Regarding the power bank getting hot, it's normal for power banks to get warm during charging, but if it becomes too hot, that could be a concern. Here are some steps you can take to troubleshoot the issue:

1. Ensure that you're using the power bank in a well-ventilated area and not under direct sunlight or in a hot environment.

2. Try using a different charging cable to see if the issue persists.

3. Avoid using the phone while it's charging from the power bank.

4. Allow the power bank to cool down before attempting to recharge it.

If after trying these steps the power bank still only partially charges your phone and gets excessively hot, it may be a defective unit. Since you've mentioned that similar issues were observed in reviews, it could also be a characteristic of this model. However, if you believe the heat issue is abnormal or if the charging performance is not meeting your expectations, considering an exchange might be a good option. "

Now, I own many Anker products, and for the most part, I love them, especially the Anker Prime 100W USB C Charger (model A2343), but I am thoroughly disappointed at Anker and this Nano Power Bank (22.5W, Built-In USB-C Connector) model A1653. I own several power banks over the years from reputable brands, but never one that doesn't perform up to it's advertised capacity. Most of the reviewers out there for this nano power bank never try using it to completely charge a phone, except this one Japanese reviewer "getget YUTAKA", who reported the same issues I discovered. This nano battery bank has extremely low efficiency and value, you will be lucky to get 3000mAh out of it, so don't advertise it as a 5000mAh battery bank, say it's a 3000mAh because that's all you are going to get.