hello all!

this inquiry on lipo batteries may be somewhat OT from the fpv scene but nonetheless bears substance for everyone’s benefit on lipo safety issues.

i recently bought a brand new mid-tier smartphone from one of the more popular brands. like every similar device it comes with an internal 5000mah lithium polymer battery. BUT this one had usb-C and a 33W wall wart allowing for fast charging capability. i tested this feature coming from 25% remaining charge after partial usage to set up the device. i did not time the whole process but i think it took a short ~15min to achieve an almost full charge. 

i also noticed the phone rear panel being slightly warm after the whole process which sparked some cause for alarm! as a long time hobbyist fiddling with lithium packs i have always adhered to the conservative 1C rating to preserve longevity and i never encountered even the slightest bit of warmth with the pack anytime. 

SO did the mobile phone manufacturer install a 100C 3.7V lipo cell inside my phone in order to withstand this kind of temperature rise during their so called “fast charging” feature? or is this potentially a recipe for imminent doom for the poor battery? 

inputs from all smartphone users are much appreciated! cheers!?

5000mah at 1C is 5A. 33W / 4.2V = 7.85A

7.85A / 5A = 1.57C

Sorry, far from 100C you are thinking.
Some people charges their LiPo at 2C or more.

I just wanted to add, that C rating on LiPo is related to discharge and not charging. LiPo are always recommended to be charged at 1C. But as mentioned above, charging at 2C should not be an issue.

A lot of the fast chargers (like USB-C PD) will deliver higher voltage to push through the higher watts (ie. 12v 3A = 36W). I guess the phone must step down the voltage so there will be some extra efficiency loss/heat generation there. If your phone charged around 75% of the battery in 15 min, that would be closer to a 3C charge rate. I believe the same applies here, if you repeatedly rapid charge your lipo/lion, you will reduce its overall life, but how much capacity you will lose going from 1C to 3C and after how many cycles is the question.
But I think the trend is clear, from electric cars to electric devices, everyone wants instant charging abilities and as long as the battery remains usable until they can push on you to upgrade to the next version then all will be fine. My phone is 5 years old, fortunately the battery is still working well, it has quick charge but I've only medium charged it mostly.

Mstc, you are so correct. I started to write what you wrote. People want fast these days without really caring about degradation. But from several source, most are saying that the degradation is minimal. So for a phone, most people switch out phones so often that the degradation is no existence. Even according to Tesla, as long as you don't charge to 100% all the time, using the Super charger all the time is fine.

The battery begins to degrade as soon as it leaves the assembly line. To reduce degradation and reduce fire hazard, chemical additives are added to the electrolyte. But they pay for this with lower output currents. In general, the manufacturer must indicate in the battery specifications what the maximum charge current is.
If a manufacturer includes a charger for a smartphone, it must match the capabilities of the battery. If it is not included in the package, then the manufacturer must clearly indicate which charger is compatible with this smartphone.

all points well taken! guess i am just too cautious bordering on paranoid taking the most conservative route on charging lipos. hopefully the phone manufacturer implemented some algorithm within the system to strike a compromise between quick charging and lipo safety.