Sage Charging time: Sage @23% Not all equal

[Quoth]

A Sage at 23% charge:
Estimated time 36 minutes with a 2A 5V USB-A port charger for a Lenovo
Estimated time 5 hours something with a 1A 5V USB-A port charger for an Alcatel.

In USB-A the D+ and D- pins can have different resistors to +5V or OV or voltages to signal to the gadget how much current can be taken. This is absolutely standard for 0.1A and 0.5A ports, but varies for 1A and 2A according to maker or even the model of device from the same maker. Apple uses a different scheme from that adopted originally by other makers.

The Alcatel phone does charge as fast as expected on the 1A PSU supplied, but almost everything else charges slower than on some other 1A chargers.

Some gadgets charge no faster on any 2A charger than on their own 1A. The Lenovo Yoga charges much slower on a Lidl 2A charger than its own.



It's not to do with USB-C vs mini-USB, USB-B or micro-USB as USB-C uses extra voltage controi serial port if the charging/PSU end is USB-C, otherwise the USB-C uses the same scheme as all other USB slaves charging, simply putting a load on the D+ and D- wires from the USB-A port and measures the voltage to decide what current can be taken.
Usually the fall back is 0.5A if the measurement isn't understood, but can be 0.1A (Original USB 1.0)

It seems that unless the Sage has the D+ and D- settings it recognises it will only charge at about 1/8th speed, about 0.3A if 2A is full speed

I can later use a special cable and measure exactly what it takes from different chargers

Conclusion
A full charge from a 100% compatible 2A 5A USB-A PSU/Charger might take 45 minutes. It might take 7 to 8 hours with an "incompatible" charger.

I don't have any 5A USB-C chargers (that's the max current). They use a separate pair of wires with serial data to negotiate charging.

There isn't meant to be negotiation on USB-A, though some smart chargers that can do 2.5A or 3A at 5V will disconnect, change the resistors/voltages on D+ & D-, reconnect, measure current taken and then set D- & D+ to the setting where the most current is taken. The connections have to be disconnected & reconnected internally by the microcontroller so the slave gadget re-detects the D- and D+ (normally used for the serial data). Some USB-A smart chargers are mistaken as computer hosts by some gadgets.

[NiLuJe]

IIRC, it "negotiates" a standard CDP 1.5A on either a Kindle charger or a power strip ~2A's port over here (and it seems to be holding to that, according to an USB meter).

Reading the PMU's driver code makes my brain hurt, but I don't think it'll ever do more than 2A anyway.

[Deobulakenyo]

My Libra 2 does not charge if i use a 5V 500mah charger from an old phone, but it does charge connected to a USB port of my laptop, and using 1A and 2A chargers.

[Quoth]

Originally Posted by NiLuJe

IIRC, it "negotiates" a standard CDP 1.5A on either a Kindle charger or a power strip ~2A's port over here (and it seems to be holding to that, according to an USB meter).

Reading the PMU's driver code makes my brain hurt, but I don't think it'll ever do more than 2A anyway.

More than 2A on a USB-A port isn't standard.

The 1.5A sounds about right for the size of cell. Likely the Lenovo 10" tablet has a larger cell and can use 2A. I must make up an adaptor so I can see what the charge current is and measure what is on the D+ and D- pins when a gadget is connected, partly out of curiosity and partly to know which chargers suit which gadgets.

Be interesting to see what the min and max currents are for all the readers and maybe put the Kindle DXG and KK3 on a time-switched charger as they go flat when not in use AND you can't set the date, so it's over a day till it works properly (or never if 3G is turned off for the DXG).