Rapid charging indicator: What triggers it? (technical question)

[PaulQ]

I am trying to get a better understanding of what causes the phone to display "Rapid Charging." This may apply to other phones as well (e.g. Samsung's "Fast" charging).

Is there a wattage point that triggers the notification or is there some sort of message in the way the power is being delivered that triggers it?

This all stems from a search I am conducting to find a portable battery that will rapid charge my Pixel 2 but I am finding one that I have is doing it quickly, no notification. Amazon reviews comment on batteries charging their phones quickly but not necessarily getting that indicator. I don't want to waste time and money looking for one that makes that word appear on screen when it really doesn't matter much.

For the record - a portable battery I used that triggered the fast charge indicator on my Mate 9, but no indicator on the Pixel 2, charged my Pixel 2 from 55% to 90% in 35 minutes. But if there's some battery out there that will provide the same charge during a 20 min ride across the city, that does make a difference for my use case.

I know I should look for PD (power delivery) but am I going to actually get noticeably better performance, like 40% in 20 min?

........ Just trying to pack more phone knowledge into my brain!

 

[GSDer]

If you take a look at something like https://www.androidauthority.com/usb-power-delivery-806266/ you'll see that the most the Pixel 2 line is capable of receiving is 18W, so if you get a PD 2.0 capable battery (using a USB-C to USB-C cable) then you'll get the fastest charging possible.
Unfortunately that doesn't really tell you HOW quickly you'll charge up, but you can be assured that it's the fastest that the design supports.
Edit: if you watched the video he mentioned charging a Pixel (OG?) from dead to 100% in about 97 minutes, and the article mentions a typical 15W charging session (from some undeclared value presumably to 100%) taking around 30 minutes. YMMV.

 

[Mooncatt]

I know with Qualcomm's Quick Charging protocols, the charger and phone do communicate with each other to if it's ok to use QC2 or QC3 before the charger steps up the voltage. So my guess is that their quick charging indicator is either based on that handshake communication and/or the actual input voltage, not the wattage.

I suspect other similar protocols from other OEM's are similar.

 

[Mike Dee]

I am trying to get a better understanding of what causes the phone to display "Rapid Charging." This may apply to other phones as well (e.g. Samsung's "Fast" charging).

Is there a wattage point that triggers the notification or is there some sort of message in the way the power is being delivered that triggers it?

This all stems from a search I am conducting to find a portable battery that will rapid charge my Pixel 2 but I am finding one that I have is doing it quickly, no notification. Amazon reviews comment on batteries charging their phones quickly but not necessarily getting that indicator. I don't want to waste time and money looking for one that makes that word appear on screen when it really doesn't matter much.

For the record - a portable battery I used that triggered the fast charge indicator on my Mate 9, but no indicator on the Pixel 2, charged my Pixel 2 from 55% to 90% in 35 minutes. But if there's some battery out there that will provide the same charge during a 20 min ride across the city, that does make a difference for my use case.

I know I should look for PD (power delivery) but am I going to actually get noticeably better performance, like 40% in 20 min?

........ Just trying to pack more phone knowledge into my brain!

You need a PD compatible battery pack and it will charge faster.

 

[PaulQ]

Thanks guys..... I am just going to buy a PD battery and take it under the YMMV convention. It's worth it to me when I am travelling in more difficult environments to have maximum charging speed.

 

[toiday]

I use generic 2.4amp charger, neither PD nor QC, Pixel 2 still show "Rapid Charging". It's still not clear what triggers the "Rapid Charging".

 

[PaulQ]

If you take a look at something like https://www.androidauthority.com/usb-power-delivery-806266/ you'll see that the most the Pixel 2 line is capable of receiving is 18W, so if you get a PD 2.0 capable battery (using a USB-C to USB-C cable) then you'll get the fastest charging possible.
Unfortunately that doesn't really tell you HOW quickly you'll charge up, but you can be assured that it's the fastest that the design supports.
Edit: if you watched the video he mentioned charging a Pixel (OG?) from dead to 100% in about 97 minutes, and the article mentions a typical 15W charging session (from some undeclared value presumably to 100%) taking around 30 minutes. YMMV.

That video was very helpful. Interesting.

At least charging may eventually become less fragmented. Wait - who am I kidding. This is Android. Of course it won't. Someone's always go to come up with their own thing.

As of Tuesday, I'll have....

A power delivery compliant battery.
A QC 3 battery.
A battery that supports Huawei's fast charging (whatever that is - I just know this one does).
A couple old school vanilla batteries from back in the day (err, like a year ago).

I just have to bring the battery that matches my phone. Seems like I have had to buy a new battery with each of my last three phones if I want fast charging. My tablet, headphones are older so they just do dumb, old charging.

Crazy.

 

[hallux]

I use generic 2.4amp charger, neither PD nor QC, Pixel 2 still show "Rapid Charging". It's still not clear what triggers the "Rapid Charging".

In your case it's the cable (which is incorrectly built if there's a USB-A port in the mix). A Google engineer, Benson Leung, went on a crusade in 2015/2016 after the Nexus 6p was released and companies building cables tried to trick folks. The bottom line is that if the phone tries to charge rapidly on a port that can't support it you risk damaging that port.

You can see a spreadsheet of his testing at https://docs.google.com/spreadsheets/d/1wJwqv3rTNmORXz-XJsQaXK1dl8I91V4-eP_sfNVNzbA/edit#gid=0

 

[Mike Dee]

Thanks guys..... I am just going to buy a PD battery and take it under the YMMV convention. It's worth it to me when I am travelling in more difficult environments to have maximum charging speed.

I have two huge ones made by Ravpower. One of them is 26800 mAh. It can charge three devices at the same time and has two inputs for faster charging. I did a review on it in the accessories section

 

[PaulQ]

I got the PD battery today. It works. Triggers "Charging Rapidly" and indeed does that. For the record, it's the...

Auckley Portable External Charger,PD Power Bank Auckly10000mAh USB Type C Mobile Power Bank,4-Port Battery With High-Speed Charging,Phone Charger Power Pack for iPhone X,iPhone 8,Samsung Galaxy S8/Note 8​

I'll use this one just for the Pixel 2 when I am travelling. I'll carry one of the others from my collection for all my other devices.

Again, thanks guys. I learned!

 

[PowrDroid]

Using the Google supplied charger and cable I've only seen the "charging rapidly" message once (that I can recall.) It was on my wife's 2 XL and the battery was at 19%. I suspect the battery must reach a designated minimum percent charge before the charger will initiate the "charging rapidly" message.

Do people see the "charging rapidly" message only when the battery has reached, say, 25% or less? Anybody have any data?

Whether or not the message is meaningful is another question. For example, suppose you plug in your phone with the battery at 30% and it charges to 90% in 75 minutes. You get no "charging rapidly" message. Another time you plug it in with battery at 20% and it charges to 80% in 75 minutes, but this time you do get the "charging rapidly" message. Is there a real difference in charge rates? In both instances the battery added 60% of capacity in 75 minutes, but only once did you get the message. Does Google simply trigger the message at lower states of charge to assure the user the battery is "charging rapidly"?

 

[Mike Dee]

Using the Google supplied charger and cable I've only seen the "charging rapidly" message once (that I can recall.) It was on my wife's 2 XL and the battery was at 19%. I suspect the battery must reach a designated minimum percent charge before the charger will initiate the "charging rapidly" message.

Do people see the "charging rapidly" message only when the battery has reached, say, 25% or less? Anybody have any data?

Whether or not the message is meaningful is another question. For example, suppose you plug in your phone with the battery at 30% and it charges to 90% in 75 minutes. You get no "charging rapidly" message. Another time you plug it in with battery at 20% and it charges to 80% in 75 minutes, but this time you do get the "charging rapidly" message. Is there a real difference in charge rates? In both instances the battery added 60% of capacity in 75 minutes, but only once did you get the message. Does Google simply trigger the message at lower states of charge to assure the user the battery is "charging rapidly"?

Mine says rapid charging whenever I plug in. It does not matter what percentage.

 

[PowrDroid]

Mine says rapid charging whenever I plug in. It does not matter what percentage.

Interesting. I'm referring to the AOD screen. Next to the digital clock I see a small lightning bolt icon whenever the phone is charging. Only one time have I seen the message "charging rapidly". This message appears in small italicized font next to the lightning bolt icon.

Mind, my phone rarely gets below 30% charge since the battery is so strong in the 2 XL and I try to practice the 40/80 rule of battery charge status. In my case it's more like 40/90.

I just plugged it in at 49% and no "charging rapidly" message.

 

[Mike Dee]

Interesting. I'm referring to the AOD screen. Next to the digital clock I see a small lightning bolt icon whenever the phone is charging. Only one time have I seen the message "charging rapidly". This message appears in small italicized font next to the lightning bolt icon.

Mind, my phone rarely gets below 30% charge since the battery is so strong in the 2 XL and I try to practice the 40/80 rule of battery charge status. In my case it's more like 40/90.

I just plugged it in at 49% and no "charging rapidly" message.

I'm referring to the bottom of my screen

 

[PowrDroid]

I'm referring to the bottom of my screen

I'll be on the look out for that.

 

[hallux]

Mine is the same as @Mike Dee sees. Any time I plug in to a charger that supports USB-PD (or is a USB-C charger providing the minimum wattage for such) I see charging rapidly, even if it's at 70% charge. In fact, I RARELY let my battery dip below 40-50%, and I can do that because I have a charger on my desk at work, one in my car and one at home (well, at least) so if it's borderline it can be popped on a charger for a boost relatively easily.

 

[PaulQ]

I see it all the time too.

Maybe a silly question - have you only been charging at one location (e.g. your home)? If so, try it somewhere else.

 

[toiday]

So many responds are off topic. This thread supposed to be What triggers the "charging rapidly" on the Pixel. So far, it's not the type off chargers. The correct type, PD, the QC, and just an regular 2.0amp, all can give the Pixel "charging rapidly" status. But why? Shouldn't it the only one that can charge the Pixel rapidly is the PD type? Why the QC and the regular one both can change the Pixel rapidly?

 

[Mike Dee]

So many responds are off topic. This thread supposed to be What triggers the "charging rapidly" on the Pixel. So far, it's not the type off chargers. The correct type, PD, the QC, and just an regular 2.0amp, all can give the Pixel "charging rapidly" status. But why? Shouldn't it the only one that can charge the Pixel rapidly is the PD type? Why the QC and the regular one both can change the Pixel rapidly?

A regular charger cannot charge rapidly

 

[Itsa_Me_Mario]

So many responds are off topic. This thread supposed to be What triggers the "charging rapidly" on the Pixel. So far, it's not the type off chargers. The correct type, PD, the QC, and just an regular 2.0amp, all can give the Pixel "charging rapidly" status. But why? Shouldn't it the only one that can charge the Pixel rapidly is the PD type? Why the QC and the regular one both can change the Pixel rapidly?

Depending on the QC version, QC can support PD. But it's really all about the amp/voltage combination and what the phone chooses to accept vs what the supply can handle. Example if that 2A charger is running on 9V, that's 18W and matches the max current the P2 can access.