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> Sudden slow charging
Pete G.
post Nov 23 2019, 06:36 PM
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Has this happened to anyone else? Usually my fast-charging Gemini comes up to full in a couple of hours, but today I came back after about four hours and the LED was still red! The status panel said "Approx 4 hours left" and "50%" ! I unplugged the USB, and replugged it (reversing the connector for good measure). A little while later it was up to 72% and has since been charging at the normal speed.

I'd guess that there is some pin in the connector or something that indicates fast charging, which somehow hadn't made contact. Does anybody know what the protocol is?
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gymbo
post Nov 24 2019, 09:20 AM
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QUOTE(Pete G. @ Nov 24 2019, 04:36 AM) *
Has this happened to anyone else? Usually my fast-charging Gemini comes up to full in a couple of hours, but today I came back after about four hours and the LED was still red! The status panel said "Approx 4 hours left" and "50%" ! I unplugged the USB, and replugged it (reversing the connector for good measure). A little while later it was up to 72% and has since been charging at the normal speed.

I'd guess that there is some pin in the connector or something that indicates fast charging, which somehow hadn't made contact. Does anybody know what the protocol is?

For me, slow charging just appears randomly once in a while (I usually charge it over night, so might be slow charging more often then I actually observe). Usually unplugging and plugging in again solves the "issue", but I have seen no particular reason WHY it happens. Only thing I can think of, is that it is related to the somewhat strange behavior , where it suddenly shuts off at different battery levels. I.e. that there is some problem with power-management in general on the Gemini...

Whatever the reason, hope it is fixed on the Cosmo...
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Daniel W
post Nov 24 2019, 12:08 PM
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QUOTE(Pete G. @ Nov 24 2019, 03:36 AM) *
Has this happened to anyone else?
For me, fast charging my Gemini has always been a bit hit and miss. When it doesn't kick in, as Gymbo said, unplugging and reconnecting the charger usually works.

QUOTE(Pete G. @ Nov 24 2019, 03:36 AM) *
...the status panel said "Approx 4 hours left" and "50%" ! I unplugged the USB, and replugged it...
Since I mostly use my Gemini at home, I've never used a lock screen, so I didn't know it could show the estimated remaining time until charged, but, well.. after a while, it does, before which it just says "charging", so I've learned something today. Thank you.

QUOTE(Pete G. @ Nov 24 2019, 03:36 AM) *
I'd guess that there is some pin in the connector or something that indicates fast charging, which somehow hadn't made contact. Does anybody know what the protocol is?
It's more involved than a pin for on or off. The "Pump Express" protocol by MediaTek doesn't seem widely documented, but I did find this (from 2016): http://cdn-cw.mediatek.com/Features/Pump%2...ntroduction.pdf

Basically, the Gemini sends a sequence of carefully timed pulses to request a particular voltage. As far as I understand, they are sent via the same pins as the actual power, so I'd guess it's more a matter of timing glitches than bad connections, which begs the question: is it the Gemini or the charger that doesn't behave reliably? That's perhaps something someone with access to multiple Geminis and chargers could look into.

According to the document linked above, Pump Express 2.0 and 3.0 (also, reasonably 4.0, from 2018) supports stepping the voltage in fine increments, but the Gemini power brick just says 5/7/9/12V and, using a USB-C power meter, I've only observed voltages close to 5Volt or 9Volt. That would suggest Pump Express+ (version 1.0) which this blog https://hasbrouck.org/blog/archives/2018_10.html seems to agree with.

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Pete G.
post Nov 24 2019, 11:46 PM
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QUOTE(Daniel W @ Nov 24 2019, 01:08 PM) *
Since I mostly use my Gemini at home, I've never used a lock screen, so I didn't know it could show the estimated remaining time until charged, but, well.. after a while, it does, before which it just says "charging", so I've learned something today. Thank you.

"lock screen"? Not sure what you mean, there. I never lock my unit, as I try to keep it close! I get the battery status panel by swiping down from the top of the screen, and tapping the battery icon in the panel that appears.

QUOTE(Daniel W @ Nov 24 2019, 01:08 PM) *
Basically, the Gemini sends a sequence of carefully timed pulses to request a particular voltage. As far as I understand, they are sent via the same pins as the actual power, so I'd guess it's more a matter of timing glitches than bad connections, which begs the question: is it the Gemini or the charger that doesn't behave reliably? That's perhaps something someone with access to multiple Geminis and chargers could look into.

Ahh, thanks... That makes sense -- and sounds like lots of opportunities for things to go wrong!

Thanks for all that info. I'll have to dig.
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Daniel W
post Nov 25 2019, 07:44 AM
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QUOTE(Pete G. @ Nov 25 2019, 08:46 AM) *
"lock screen"? Not sure what you mean, there. I never lock my unit, as I try to keep it close! I get the battery status panel by swiping down from the top of the screen, and tapping the battery icon in the panel that appears.
When plugging in the charger, the Gemini needs some time to figure out the remaining time estimate, and I didn't wait long enough. By the time I tried using a lock screen, the estimate was available, and I failed to realize that, by then, it would ALSO have been visible on the status panel, as well as in the main settings menu. So, now I know three ways to check it, two of which does not require a lock screen, which is nice, as I currently keep next to nothing sensitive on my Gemini anyway.
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gidds
post Nov 26 2019, 03:39 PM
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I'm surprised more people haven't considered the advantages of slow-charging:
  • You can use any USB charger.
  • Prolongs the life of the battery.  (Stays cool while charging.)
  • Ideal for charging while you sleep.
I've got into the routine of plugging my Gemini in when I put it down on my bedside table and go to sleep; it's always charged when I wake, and always lasts the day.

Of course, everyone's lifestyle is different; but there's at least a chance that I'm not the only one it's ideal for… smile.gif
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