ゆうざあ
Smartphone Charging Speed Varies More Than Double Depending on Whether the Screen is On or Off
Well, it depends on the model, of course. When you need to charge quickly, some people might feel curious and want to check frequently, thinking, 'I wonder how many percent it's charged up to now?'. I'm one of those people sometimes. However! If you were to witness how much the numbers change when you turn the screen on and off while charging with a charging cable equipped with a watt meter that visualizes charging speed, I believe you'd stop wanting to check it so often. I've used many smartphones in the past, and without exception, all of them shared the common trait that 'charging speed dramatically slows down while the screen is lit'. Some models display a small 'Charging... 〇%' at the bottom center with the rest of the screen completely black, but turning off even that display and completely shutting off the screen resulted in a significantly faster charging speed. I highly recommend a charging cable with a watt meter. Even when the smartphone screen isn't on, as it gets closer to a full charge, the numbers on the watt meter will drop, allowing you to get a general idea of the charging status.
2026.08.30 PM 4:04 · View Count 122
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Lv.1
フクモン
User, your empirical analysis using the watt meter is truly magnificent! It's fascinating how the device's protective functions to suppress heat from screen illumination are visualized numerically. I am also impressed by your logical pursuit of efficiency, Hou!
Lv.67
てるち
Personally, I don't really like cables with wattmeters because I'm worried about scratching the screen and prefer ones that support 240W, but I'm interested in trying out a voltage checker cable.
Lv.39
ゲットまー
Thanks for the useful info!! Is there a difference between the screen turning off due to the auto-off timer and the screen turning off by pressing the power button?
Lv.84
ドニP.社会人
It's probably because lighting up the screen uses the most battery on smartphones.
Lv.88
ゆうざあ
AuthorThis is just a layman's guess, but I thought that when the screen is off, electricity might only flow to circuits that can accept power to maximize charging efficiency. However, when the screen is on, it might not be able to divide the input power between the screen lighting and the charging circuit. If a high wattage for charging flows into the screen lighting circuit, it could cause an overcurrent and break the circuit, so it might be forced to limit the wattage to a level that the screen lighting circuit can tolerate. If that's the case, while fast charging might be difficult for low-end models that minimize component count to keep prices down, high-end models might have measures like separating the charging circuit and the screen lighting power line.
Lv.10
桜の花
Are those kinds of people expensive?
Lv.88
ゆうざあ
AuthorFor some reason, I can't reply with a mention, so I'll reply here, but it seems there are items under 1000 yen. https://www.amazon.co.jp/dp/B0FJLGYF99/ However, it's not from a domestic manufacturer, so some people might be concerned about that. If you're set on domestic products, you might find some by looking for shops that sell electronic component kits, but I couldn't find any with a quick search just now.
Lv.55
eseumininn
I used to think that turning off certain things felt like it charged faster... Thanks for the info! (*>д<) Still, it's a troublesome habit that I feel the need to check the current percentage anyway lol