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Quoth · 01-30-2023, 03:23 PM

There are unfortunately different incompatible specs for USB charging. If the device doesn't make sense of it then it defaults to a slow charge.

My charger came with a USB-C device (the Lenovo tablet), but it's a USB-A outlet charger, so only sets resistors or voltages on the regular USB D+ and D- lines. I'd expect the Sage and many other 5V 1.5A USB C devices are really just updated USB 2.0 micro USB designs using regular USB-A charger signals. The advanced actual USB-C chargers use separate serial digital communication wires from the regular USB D- and D+ twisted data pair. The device tells the charger what voltage to use and what current it could take. The host charger tells the device if it can do those volts (up to 20) and what current it can do. That's charge negotiation.
Any charger with a USB-A socket does NO charge negotiation. It only does 5V ever, and puts static voltages or resistors (depending on spec) on the D- and D+ lines as data is not used. The device interprets that to decide on current to take. You could have a 5V 4A supply and without the valid setting the device expects on the D+ and D-, then the device only takes 500mA.
I have loads of 1.5A and 2A USB chargers. But the Sage only does the 45 minute charge (maybe between 1A and 1.5A) on one of them. The rest take more than twice as long, so obviously the D+ & D- isn't what the Sage is looking for so it only takes 500mA.

A USB-C 65W charger obviously isn't communicating via USB-C power serial connection with the Sage.

I have also Libra 2, Elipsa and the Lenovo, all USB-C. They all charge slow on my PC's USB-C port, which is certainly able to do 2A.

Fortunately for 5V USB gear, the default for PC USB-C port or a USB-C based charger is to give 5V, not 20V!

01-30-2023, 03:23 PM	#61
Quoth Still reading Posts: 14,255 Karma: 105299897 Join Date: Jun 2017 Location: Ireland Device: All 4 Kinds: epub eink, Kindle, android eink, NxtPaper	There are unfortunately different incompatible specs for USB charging. If the device doesn't make sense of it then it defaults to a slow charge. My charger came with a USB-C device (the Lenovo tablet), but it's a USB-A outlet charger, so only sets resistors or voltages on the regular USB D+ and D- lines. I'd expect the Sage and many other 5V 1.5A USB C devices are really just updated USB 2.0 micro USB designs using regular USB-A charger signals. The advanced actual USB-C chargers use separate serial digital communication wires from the regular USB D- and D+ twisted data pair. The device tells the charger what voltage to use and what current it could take. The host charger tells the device if it can do those volts (up to 20) and what current it can do. That's charge negotiation. Any charger with a USB-A socket does NO charge negotiation. It only does 5V ever, and puts static voltages or resistors (depending on spec) on the D- and D+ lines as data is not used. The device interprets that to decide on current to take. You could have a 5V 4A supply and without the valid setting the device expects on the D+ and D-, then the device only takes 500mA. I have loads of 1.5A and 2A USB chargers. But the Sage only does the 45 minute charge (maybe between 1A and 1.5A) on one of them. The rest take more than twice as long, so obviously the D+ & D- isn't what the Sage is looking for so it only takes 500mA. A USB-C 65W charger obviously isn't communicating via USB-C power serial connection with the Sage. I have also Libra 2, Elipsa and the Lenovo, all USB-C. They all charge slow on my PC's USB-C port, which is certainly able to do 2A. Fortunately for 5V USB gear, the default for PC USB-C port or a USB-C based charger is to give 5V, not 20V!