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OESF Portables Forum _ Gemini PDA - Hardware _ Charger Voltage 9V

Posted by: Eldkatten Jun 1 2019, 08:16 AM


I've just bought a handful of new chargers (GOOBAY 45173), because with the charger I used only about 0.5 A at 5V was provided during charging, while the charger as such can output up to 2 A. Other devices use that range and charge with 1.3 - 1.6 A at 5 V.
I have a little gizmo connected between the charger and the cable, which shows me the voltage, the current and things like mAh and mWh provided so far.

When I connect the Gemini to a power bank, it draws about 1.4 A at 5 V.

What I see now, with the new charger, is that after I connect everything, the voltage starts at 5V (which is ok for USB), but after a few seconds jumps up to 9V and remains. The current is about 1.5 A.

I read the technical description of the charger now (why bother before using it? rolleyes.gif ), and it says that it supports Qualcomm Snapdragon charging process. So I guess with this particular charger the Gemini switches to the fast charging process.

I would appreciate if someone could answer the following questions:
- Is it really ok to provide 9V through USB structures? I mean, everything is originally designed for 5 V.
- Actually I don't want the Gemini to fast charge. I don't trust the process concerning battery life, and the Gemini and the charger get pretty hot while charging. Is there a way to tell the Gemini not to fast-charge, even if the charger supports it?

Kind regards

Posted by: DJO Jun 2 2019, 02:43 AM

The original Planet charger supplies voltages up to 12v so 9v should be OK.

If not your Gemini would probably have already released the magic smoke and died.

Posted by: gidds Jun 2 2019, 07:06 AM

As I understand it, 5V is the standard USB voltage, so all power supplies start with that.  If a device can charge at a higher voltage, it has to request it explicitly.  (And we're slowly settling on the standards for that.)

So if you see a higher voltage, it must be because the Gemini has asked for it.  And it's a fair bet that it wouldn't request a voltage it couldn't handle… smile.gif

Posted by: Eldkatten Jun 2 2019, 09:47 AM


ok, thanks ya'll. I was rather worried about my "gizmo", but I now read in the technical destription (why bother before using it? blink.gif ) that it can handle voltages up to 24V. So I guess this is safe.

I think I'm going to start another thread on my question about fast charging, so thanks again so far.

Kind regards

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