Anker 621 Magnetic Battery

The color matches the new iPhone 17 in lavender. The charging is ok, it makes the phone pretty warm and is only good for 1 full charge or several partial charges. It's small, light and works in a pinch which is why we have it.

This was my first Magsafe battery. I had some older Qi wireless chargers and was familiar with heating issues. But these were older and lower power. Without the Magsafe feature, they were finicky and fussy and didn't properly fit around camera lens protrusions. I barely used these devices. This Anker 621 has a lot of promise. The Magsafe feature locks tight and the dimensions do not interfere with the camera protrusions, even with a case on the phone. It's compact and slim, and most importantly, does not require wires. It can be easily carried in a backpack or pocket without an accessory bag for wires and cables. When I first unpacked the battery, I fully charged with with a USB-C PD charger. It charged at 1A/5V. I used it to inductively charge my iPhone 14 Pro intermittently over the next few days. After about 10% charge, I determined the heat buildup to be intolerable. Therefore, I only used the pack intermittently. That worked fine for me over several days. When the battery was empty, it took 20Wh to fully charge. The battery was advertised for 5000mAh, which is impossible to measure without disassembling the unit. However, we can calculate 20Wh / 5V / 0.9 = 4400mAh (where 0.9 is the efficiency of the voltage converter for USB). This is below advertised capacity, but there’s a lot of assumptions in the conversion. Then I used a USB-C cable to charge my iPad Mini. It transferred 14.8Wh at about 9 Watts before exhausting. The round-trip efficiency was high, because recharging took 14.8Wh to fully recharge. I suspect I didn’t get the full 20Wh capacity with the iPad because the higher charge demand choked the battery before it could get fully empty. Using the inductive charge mode, both devices get hot relatively quickly. The switching power electronics get particularly hot. I can easily feel where the transistor is located beneath the plastic shell. The inductive transmitter loop gets warm on the battery and the receiver loop gets warm on the phone. Lithium-ion batteries degrade proportionally to temperature (the Arrhenius relationship), accelerating +25% degradation rate for every 10C, this is bad for the phone. In summary, • The battery delivers 20Wh of energy. If using inductive (Qi and Magsafe), much of the energy is converted to heat, so perhaps only 10-15Wh is actually delivered to the battery. • If using high-current devices using a charge cable, such as an iPad, the high current chokes the battery a bit early, stopping at 15Wh. • My back-of-the-envelope calculation shows 4400mAh vs. rated 5000mAh. I suspect the battery is not delivering rated capacity. Anker should be rating these batteries in Joules (watt-hours) instead of Coulombs (ampere-hours). • Inductive charging is inefficient, losing a quarter to half of energy to heat. This is not Anker’s fault but a result of real-world physics. With my iPhone 14 Pro, I saw about 10C rise per 10% of battery charge. I never let it progress beyond this point. • Lithium-ion batteries accelerate aging degradation due to the Arrhenius relationship about +25% per 10C temperature rise. Therefore, prolonged use of inductive charging will ultimately age your battery prematurely. • This battery is very worthwhile because I don’t have to carry an accessory kit with wires to use. Just slap it on the back of the phone and go. Plus, if frees the connector to use with wired headsets when using.

Durable I’ve had it for 2 years and it still works great, it’s portable, it kinda gets warm when in use.

This battery has honestly changed the way I travel. It only charges my battery up to 70% but for me that’s more than enough. The slim design makes it easy to carry to the point I don’t notice I have it in my pocket. I’m giving it 4 stars only because the battery does get hot but besides that I like it

Before ordering I had struggled to get answers to some basic questions about how this battery works, so now that I have it in hand I'm hoping these tips are useful: - The battery charges the phone wirelessly when the battery is attached to the phone magnetically and turned on. - While the phone and battery are attached the power moves in only one direction from the battery to the phone. The battery doesn't charge wirelessly when attached to a phone even if the phone is plugged in. - The battery must be charged independently of the phone. It can be charged either by plugging a USB-C cable into it directly or by putting it on any wireless charging pad. - You CAN plug a USB-C cable directly into the battery to charge it while it's attached to the phone and while it's actively charging the phone. It's possible this isn't recommended, but it does appear to work. - The battery blocks the phone's Magsafe charging area while it's attached to the phone, but the phone can still be charged directly via USB-C with the battery attached. - The battery can't be charged wirelessly while attached to a phone since it must be placed Magsafe-down onto a wireless charging pad. - The battery just barely fits into the space between the camera protection area and the bottom edge of a standard phone case with very little room to spare. The magnets are very effective, though, and it stays firmly attached to the phone. - A short USB-C cable is provided, but you need to provide a USB AC charger or wireless charging pad.

Charger gets very hot. Even with full charge on battery pack, it does not charge my phone to 100%. It works in a pinch, but charges very slowly. The battery also takes a long time to charge to full capacity. I have an iPhone 16 pro that’s barely a year old so it should have no issues itself. Like mentioned, works in a pinch, but only temporarily and would not sustain being a battery pack for a whole day or traveling and using phone consistently

Just received this to replace another same type battery but that one would go on then just shut off for no apparent reason. I do have an IP-12 and i use a pretty heavy case so i wasn't sure how these type of batteries were going to work. I installed the metal ring on back of case and as it held battery ok it just wouldn't charge. So i bought this Anker to try it as i do like Anker batteries. Well right away it stuck right to my case and immediately started to charge. I was still skeptical. I just waiting to see if it shuts off and it never really did. Yes it gets warm just like the other battery, but that's the characteristic of this type of charging. But I have to tell you this thing grips much better than the other battery I had, maybe it has something to do with being a MagSafe battery I don't know that's why I wanted to try the Anker as its not a Magsafe but a Maggo and boast that it has a much stronger magnet, and I can Contest to that. It's not the fastest charger but it does charge. It is probably taking me an hour and a half hour to go from 60% to 95% for me that's OK. It's meant to be more of a rescue battery to basically get you through the rest of your day, my phone that has relatively small battery. This battery probably would charge it fully but The newer phones have larger batteries. This probably will maybe get you 80% which is just enough to get you through the rest of your day. Yes, heat is a factor and some people complain about it and some people understand It's a necessary phenomenon in this kind of charging, this case with the heat temperature gun i saw 134 degrees at its peak but it does go thru cycles of heat and cool as internal thermostat kicks in. To me thats a minor inconvenience, but it does not heat up your phone. The heat stays within the battery itself and it does not radiate to your phone. So far so good i using it now to write this and as the charge percent is not rising as fast as it did when I wasn't using the phone. It's basically holding the percent at one particular spot right now. So in closing, if you have a heavy duty case, try it, it might work get the rings and put them on the back of your case and see what happens. My rings came with a template which is not easy to use with a heavier case so what I did is I attach the ring to the actual battery And I moved the battery on the back of the case where I found a nice spot where the phone always went on charge every time I hit that spot and then I remove the plastic on the ring went back to push the battery down on that spot removed it push the ring down by hand make sure it was good And that's it, sometimes that's more accurate than using a template. I do agree that the thickness of the case plays a big roll in whether this will work or not, but what do you got to lose if it doesn't work you can return the battery or buy a new case that's thinner and will work better.

A very good power bank, pretty light and easy to carry. It stick very well to the phone and it charge it pretty fast!