[LG G6 Real Life Review] adorable:
Decided to get some more accurate measurements of the charging speed.

Update 3 --

Bought a Motorola SC-22 QC 3.0 charger to test.

(charging graph 6 and 7)

Tested twice - once with Always on display is set to on, dim - another with the phone powered off.

Used the same cable as before in Update 2, just a different charger.

With the Motorola charger, the FAST CHARGING indication appears; with the Samsung charger, it does not appear.

Interestingly, the Motorola QC 3.0 charging speed is a touch slower than the Samsung charger, more noticable at the 90%-100% charging range.

The QC charger supports 9v and 12v for 18 watt charging, but the LG seems to max out at about 1.259% per minute while the test with the Samsung charger is a touch faster at 1.2619% per minute in the 0-80% charge range where the battery is charged at the fastest rate possible. In the 90-100% range, where the battery current is severely limited by the charging circuit to prevent the battery from exploding and damage, again, the LG G6 charges faster with the Samsung charger at 0.55%~ whereas the QC Motorola charger is slower at 0.46~% per minute.

This suggests the charging speed whether through normal, PD, or QC methods are all controlled to be under a set % per hour, and this always drops once the charge reaches about 90% to a slower charge rate. The 90-100~ minute total charge time matches what LG states for the G6.

Between the two, QC on the OEM charger or a compatible on will probably be the "best" choice for most users in extending battery lifespan since that's the tooted advantage of using QC 3.0. No published documents on whether LG has implemented any technology to increase the battery lifespan while using PD or regular chargers. On the other hand, a PD charger will probably be the best choice for those that want a slightly faster charge, and device charging compatiblity with other modern PD-compatible devices like tablets and laptops that use PD for charging.

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Older posts:

This test is done using the Samsung S5 charger so you can see how fast it charges using a standard 5V 2A charger.

Will need to get my hands on a QC charger to test for differences.

Update 2 --

4th test charging - LG G6 H873 8.0 Always On Display On w/Samsung Charger ETA-U90JWE 5V/2A

The generic USB-A to C cable I was using broke, so I used a LG G2 USB-A to Micro-USB with a Micro-USB to C adapter with the same Samsung charger.

Interestingly, the charging speed is much improved suggesting that cables also make a big difference.

1.26%/min from 25-78%

0.92%/min from 78-90%

0.53%/min from 90-100%

Update 1 ---

3rd test charging - LG G6 H873 8.0 Always On Display On w/Samsung Charger ETA-U90JWE 5V/2A

0.816%/min from 11-82%

0.615%/min from 82-90%

0.333%/min from 90-100%

130 minute total charge time from 11% to 100%

PRIOR post ---

LG G6 H873 8.0 Always On Display On w/Samsung Charger ETA-U90JWE 5V/2A

0.825% per minute added to the battery from 38% to 90% (nearly linear), then the speed drops to 0.357% per minute from 90-100% (decreasing charge speed).

Estimate total charge time based on this data from 0-100% is 137 minutes, or just over 2 hours.

With Always On Display off, 0.85% per minute from 40-91% (nearly linear), 0.36% per minute from 91-100%.