45 Watt charging is just a number

[donm527]

https://9to5google.com/2022/03/10/galaxy-s22-charging-45w-comparison/

 

[Go0gle]

No phone will charge at it's maximum rate for very long - a number of conditions have to be met for it to actually pull 45W such as battery temperature and being towards the middle of the battery percentage range. Towards the end of the charge for example, every phone cuts wattage dramatically, and often trickle charges the last 5-10% or so to protect battery health. So when you see 45W charging, that is not 0-100%, it means there is at least some period within that charge where it will accept 45W, and that is the same for virtually every mobile device using a lithium battery. It's mostly about managing heat, ensuring the battery does not swell, and also protecting battery longevity.

I plugged my S22U into a wattage meter and charged it with a 60W charger. It mostly pulls ~18W, then it jumps up to 45W for a bit, then drops down to ~10W towards the end of the charge. Very much in line with expectations. My 2018 iPad Pro with 30W charging behaves exactly the same way, it will charge at 30W for a while during the middle of the cycle, then falls of dramatically as it gets closer to 100%.

They could for sure get the phone to charge faster, but the battery would also degrade much faster, so from Samsung's point of view it is a balancing act between charging speed and longevity. It charges pretty fast already, and I suspect most people would rather have a battery that lasts 3-4+ years instead of 1-2 years and a 20 minute faster charge or whatever.

With existing LiPo technology anyway, I suspect those phones with 120W charging have much faster battery degradation.

 

[recDNA]

I needed to buy a block anyway so I got 45 watt. At least it's future proof!

 

[mike7877]

Like many of you I am Ultra excited to get my new device. Since I ordered a custom color I know my wait will be long so to pass the time I've been watching as many videos on the S22 series, mostly the Ultra, as there are being released. I don't care for the camera videos too much because most of the images look the same to me on screen. With the announcement of 45 Watt charging though I've found a new category of video, the charging comparison, which has lead to some new discoveries. Like did you know that OnePlus has an 80 Watt charger? Yeah neither did I.

Which brings me to the title of this thread. I thought if 25 Watts was fast 45 Watts would be ridiculously fast. I mean it's almost double, right. Well imagine my disappointment when 45 Watt charging is only 12 minutes faster than 25 Watt charging. Yeah you read that right. I've watched about 3 videos now and in the first one I watched the difference was like 3 or 4 minutes. I couldn't believe it so I went looking for another. I found the one attached in this thread. The difference being that the vlogger specifically mentions that not only do they have a 45 Watt charger but they also have the thicker cable recommended to be used with it. This all sounded promising and I thought that is the key, but 45 Watts ended up only being 12 minutes faster than 25 Watt charging.

In both videos the S22 Ultra failed to reach 50% by 20 minutes, which is what they claim, but only by a few percentage points each time. Somewhere in the neighborhood of 44%. Even so 44% after 20 minutes still works out to a full charge at around 50 minutes. The charging cycle really must slow down as it approaches a full charge, which most of us know and expect, but a mere difference of 12 minutes is very unexpected. The vlogger even states that they performed the test multiple times with similar results.

So what do you think?

My reply is exactly what you're looking for - I didn't read the whole thread, so some info might have already come up, but my post has everything in order and together. If I took out things already mentioned just for the sake of not repeating it, my piece would be senseless!

So:
Li-ion batteries in phones (and every device that uses them) are charged first with constant current, then constant voltage.
The voltage range is 3.2V (0%) to 4.3V (100%).

Say you apply 10A to the battery and it's at 3.5 volts. That's 35 watts. The voltage rises to 3.9V because of the current entering the battery.
As time goes on and the battery fills, the voltage starts to rise. Once it reaches 4.3V, the constant current stage is over, and the constant voltage stage begins. As the battery is filling, the resistance at 4.3V keeps rising (there's less space for the electrons). This rise in resistance results in the fall of current.
Once the current reaches about 10% of initial (so 1A in this case - 10% of 10A), charge is complete!

Important to note:
The higher the initial current, the faster the constant current stage ends and the current begins dropping during the constant voltage phase.

High currents and constant voltage phase is hard on batteries. It's better not to use the 45W charger past 50-60% if you want your battery to last long. If you're interested, check out the thread I made about charge speed of S22 with 25W chargers in this subforum - there's a big part on maximizing battery life

The 45W charger is only really helpful in the case where you need to constantly use your phone. You can keep it between 10 and 50% - use it for a couple hours, and when you're taking the mandatory 15 minute break you should take every 2h (actually it's 5-10 minutes every hour but whatever... same thing for the phone). Otherwise, you're just damaging the battery for a few minutes faster charge to 100

edit: also worth noting is that most batteries charge to 4.2V.
Phone batteries seem to be, by default, higher. Starting at 4.3, and include 4.35 and even (an absolutely ridiculous sounding {to me anyway}) 4.40!!!
It is probably so that 100% state of charge can be reached faster (I've experimented with charging lithium batteries to higher voltages and you can get up to 90% instead of 70% before the constant current stage of the cycle ends. I didn't do hundreds of cycles to see if it was especially damaging to the batteries, but I think that there's probably a reason the replacement batteries for newer phones are usually only 4.3 or lower now

 

[Hardhat Harry]

I use a Samsung wireless charger. I'm happy. My S22 is happy. No muss, no fuss. No broken cables.

 

[Laura Knotek]

I use a Samsung wireless charger. I'm happy. My S22 is happy. No muss, no fuss. No broken cables.

That's what I use also.