Just to go down that rabbit whole a bit more.
Assuming any charging increses the temperature (Even 5V .5A does), would the longer charging with less temperature be better than fast charging with higher temps?
My S10e with it’s provided Powersuply charges from 20%-80% in about half an hour or so. It gets warm to the touch, but not hot.
So, cutting the voltage in half would mean double the time to charge (not really, but about there), while heating up the battery a little less. I’m not sure which is a net positive here.
And i guess without a multi year study we won’t know for sure. All i’ve found on that is stuff that’s done on much older charging and battery technology. So isn’t comparable.
But is the outcome of that negotiation convenience or longevity?
Also: Price for micro electronics/components is not realy an indicator of quality.
And a resistor between the data lines can be used to tell the device how much current it is allowed to pull.
LiPo batteries for models have a simple rule of thumb:
Charge with 10% the current of total capacity.
So a 7500mAh pack is to be charged at 750mA.
Phones with their 3000mAh batteries should charge at 300mA, instead they charge at 3A (or more)…
I once charged a 12Ah 3-cell LiPo pack at a overly high rate. The temperature sensor of the charger was programmed to kill charge current at 70°C. Took all of 10 seconds to stop charging.
“Warm to the touch” can mean the electrolyte is boiling in the battery…
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I’m preety confident that samsung is negotiating a Charging speed that healthy enough for the battery to last two years, which is all i personally expect. Then again, trusting Samsung with batteries maybe isn’t a good idea 
The question was if longer charging with a certain temperature is better than charging shorter with a certain higher temperature.
Yeah, and i can go ahead and get an 18650 LifePo Cell that is rated at 1100mAh and has a rated max. Chargeing current of 4Amps and a recommended one of 1.1 Amps, so 100% Capacity.
The point is, charging slower won’t hurt. Definitly. I’m just not convinced that charging with higher Current but shorter is necesarily as bad as you make it sound. And phones have temperature sensors too. They also stop charging as fast at a certain point etc.
That one time Samsung had 2nd party batteries in their phone… Samsung makes good cells, like Panasonic and LG.
Holding a 40C hot object for 10 minutes is fine, holding a 400C Object for 1 minute is not fine.
That’s pretty big difference though.
Being out for 60 Minutes at 35C or 30 minutes at 40C is a closer question, and probably closer to what we’re talking about here.
Sure charging a Battery to the point it gets 100C hot is not great. But 50C or 40C is not as clear cut and closer to reality.
Capacity (mAh) = current (mA) x time (h)
A charged 3200mAh 3.7V LiPo cell, assuming no losses, is 3200mAh * 4.1V = 13.12Wh
The safe way: 10 hours at 1.3 Wh capacity increase per hour
The quick charge way: charge to 20% at 1.3Wh per hour, then switch ramp the charge rate to 10.6Wh per hour.
See above example, it is as close to how it happens as it gets.
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Well charging for long is not a good thing and I’ve learned it when I used to use a 1A charger on my old Moto G. Point is finding a good middle ground and I’m just being courious here, trying to experiment. I don’t want to piss anyone off with my comments and I’m open to criticism. Also DIYing stuff is a really attractive thing for me.
Like you said quick charging is used because it’s a feature, people like it and they’re more keen on throwing their phone out if the battery is dead. And companies don’t even care if the cell lasts one year, battery are never covered by warranty (unless they start exploding on their own in many cases like the Note 7 ones did).
I didn’t know I was about to touch a really controversial topic talking about batteries, charging and so on.