Kindle reader charge rates

[Richwood]

Per some of the info printed on the back of all Kindle readers the maximum charge voltage and current is listed. All I have except the latest PW4 and Oasis G9 and G10 list maximum input as 5.2V and 500 mA. The current PW4 lists a max charge rate as 1000 mA and both the Oasis G9 and G10 list a maximum charge current of 1500 mA at the same 5.2V max. Many older computers with USB2 ports are limited to the 500 mA output and the Amazon basic charger is 5 watts or 1000 mA output. Overpriced IMO as is the Amazon similar 9 watt wall wart charger. In comparison some of the latest Apple devices, and others, have charge rates of up to 90 watts with USB 3 ports.

The PW4 and Oasis 7" models should charge considerably faster than older models if a modern USB charger with at least 7.5 watts power output is used along with a heavy duty USB 2 cable. The reader's internal charging controller actually controls charge rate so a USB charger or battery pack with greater current output capability will not damage the reader. Otherwise I would have fried all my readers long ago.

[Barbara1955]

I noticed when I charge my eReaders with a Battery boost it dies quickly. With my PC last about a week. Plugged into the wall 1 month. strange

[Quoth]

Yes, it's ALWAYS the slave, the gadget, that decides what charging current to take, even on USB C.

A USB "A type" host port or charger signals usually with fixed voltages or resistors on the data lines of USB what current can be supplied.
The standards are only universal for 100mA (original USB 1) and 500mA. Apple may use a different standard for 1A and higher.
If the gadget doesn't understand the "signals" (they are not actually serial data), it may assume 500mA, or even 100mA.
The 5.2V is likely an absolute maximum and usually there is little or no difference between 4.8V and 5.2V.

If the Host voltage is too low the gadget stops charging. If it's too high it's destroyed.

The USB C hosts/chargers have two distinct modes: (1) The output is 4.8V to 5.2V and it works like a USB A port. (2) The output can be a much higher voltage so that say 2A is very much more power, more like a laptop charger (which are 14V to 20V depending on models). I don't remember what the maximum voltage is.

100mA gadget: Any charger/host port
500mA gadget: Any USB 2.0 host port or 500 mAcharger. Some USB 1.1 Host ports.
1000mA (1A), 1500mA (1.5A), 2A etc: The charger that is recommended or came with the gadget as not everyone uses the same scheme. Otherwise charging is only at 100mA or 500mA
Some laptops with USB 2.0 or USB 3.0 Type A host ports can supply more than 500mA, but the gadget only takes more than 500mA if the scheme is compatible. So a 1A Apple thing (maybe a USB DVD drive) will work on a same generation Mac and most later ones, but may not work on ANYTHING else, even a powered USB hub, because it can't "see" the condition on the USB D- and D+ pins that mean 1A or more available for a USB gadget.

Some "Battery" power packs are rubbish. The weight can be guide. Some use the older laptop type metal cased round Lithium cells and some use the flat bagged Lithium cells (Li Poly). A few mad ones use disposable cells!
I've a pocket one with a solar panel which would need desert sunlight to charge it even in a day. It might take many days outdoors here and won't charge with normal indoor lighting. A solar panel able to charge a gadget in real time would be quite large!

[Richwood]

Quoth;

Also older or cheap USB power/data cables can limit charging current too. Current heavy duty USB Micro or USB C charging cables can be rated for up to 3A at 5V nominal and some USB C cables for 5 A at 20V. Older cables may only be good for 500mA at 5V per what I have read.

[Richwood]

Older Kindle reader exceptions to the 0.5 Amp charge rate limitation. The Kindle 2, Kindle DX and Kindle Keyboard all list 0.85 Amp as the maximum charging current. The Kindle 1 used a dedicated round connector charger and the original USB A computer interface. No battery charging via the USB connector as I recall. Apparently the charging current limit dropped to 0.5 Amp starting with the Kindle NT and Kindle Touch. Based on listed limits all Kindle readers except the Oasis models should charge at maximum speed even with the Amazon 1 Amp 5 watt wall wart charger.

[Quoth]

Originally Posted by Richwood

Quoth;

Also older or cheap USB power/data cables can limit charging current too. Current heavy duty USB Micro or USB C charging cables can be rated for up to 3A at 5V nominal and some USB C cables for 5 A at 20V. Older cables may only be good for 500mA at 5V per what I have read.

Older cables unless total rubbish are OK for 2A. It's just copper wire and usually not very long. Ohms law rather than magic applies.

The charger/port "signals" what is possible and the gadget decides what to take. So if Gadget is 2A and the host port is 0.5A (500mA), the gadget charges fine at 500mA. If the gadget software/hardware can't make sense of the state of the D wires it takes 100mA or 500mA.

The only major difference with a power plug vs a USB connected charger, is that a charger with a power plug must be able to do AT LEAST the full current as there is no mechanism to tell the gadget what to take.
Devices will always take less than the stated current and voltage as those are absolute maximums.

USB C is more complicated, but the higher voltage modes are so to avoid having copper wire any heavier than USB - A port hosts. There are all kinds of compatibility issues and also quality issues on USB C chargers as the charger is no longer a fixed signal, 5V only and limited current.

[ilovejedd]

Originally Posted by Richwood

Per some of the info printed on the back of all Kindle readers the maximum charge voltage and current is listed. All I have except the latest PW4 and Oasis G9 and G10 list maximum input as 5.2V and 500 mA. The current PW4 lists a max charge rate as 1000 mA and both the Oasis G9 and G10 list a maximum charge current of 1500 mA at the same 5.2V max. Many older computers with USB2 ports are limited to the 500 mA output and the Amazon basic charger is 5 watts or 1000 mA output. Overpriced IMO as is the Amazon similar 9 watt wall wart charger. In comparison some of the latest Apple devices, and others, have charge rates of up to 90 watts with USB 3 ports.

The PW4 and Oasis 7" models should charge considerably faster than older models if a modern USB charger with at least 7.5 watts power output is used along with a heavy duty USB 2 cable. The reader's internal charging controller actually controls charge rate so a USB charger or battery pack with greater current output capability will not damage the reader. Otherwise I would have fried all my readers long ago.

Unless you're referring to MacBooks, Apple devices only charge up to 30W max.

iPad Pro: USB-PD 15V/2A
iPhone: USB-PD 9V/2A

I suffer from too many devices so I've got this (10 ports, 12W per port max, 60W total shared):
https://www.amazon.com/Anker-10-Port...dp/B00YRYS4T4/

paired with some dedicated Lightning and Micro USB cables as well as a couple of 3-in-1 cables for flexibility:
https://www.amazon.com/Anker-Powerli...dp/B071WNQYV6/

Also carry this 2-port charger in the purse:
https://smile.amazon.com/Anker-Charg...dp/B071YMZ4LD/

When I first got the PW4, I was pleasantly surprised to note that it seemed to be charging faster than the PW3 so I measured with a USB meter and it does pull 1A.

[Quoth]

The original USB 2.0 host spec only allowed 2.5W per port (500mA). Apple first had a non-Charged USB peripheral that needed more than 500mA (1A = 5W). For a long time some USB devices that were not charged came with Y cables to use two host ports for power. Such as 4G modems in 2008 and still even recently some USB HDDs.

The 30W is SIX AMPS at 5V, no single regular USB device uses that, 10W is the highest and most of those will charge at 2.5W if the host port doesn't have the signalling they desire.

USB-C is a completely different thing as the Gadget doesn't just "see" what current is available but can "ask" for more than 5V. IMO should have used a different system altogether. It's a bad design.

There is no absolute universal standard for more than 500mA (2.5W) on regular USB - A style host ports. Apple invented their own and some use it. Others use a different setup.

[ilovejedd]

Originally Posted by Quoth

The original USB 2.0 host spec only allowed 2.5W per port (500mA). Apple first had a non-Charged USB peripheral that needed more than 500mA (1A = 5W). For a long time some USB devices that were not charged came with Y cables to use two host ports for power. Such as 4G modems in 2008 and still even recently some USB HDDs.

The 30W is SIX AMPS at 5V, no single regular USB device uses that, 10W is the highest and most of those will charge at 2.5W if the host port doesn't have the signalling they desire.

USB-C is a completely different thing as the Gadget doesn't just "see" what current is available but can "ask" for more than 5V. IMO should have used a different system altogether. It's a bad design.

There is no absolute universal standard for more than 500mA (2.5W) on regular USB - A style host ports. Apple invented their own and some use it. Others use a different setup.

As mentioned, the 30W for iPad Pro is USB-C PD at 15V/2A.

Highest consumer chargers you can find with USB-A is 5V/3A for Qualcomm QuickCharge and that one also downgrades to 500mA (iirc) if the requesting device doesn't provide the correct signaling.

The Anker charger I posted works on both my Android and Apple devices (and PW4) at 10-12W.

But yeah, USB-C is a mess.

[Quoth]

Originally Posted by ilovejedd

Highest consumer chargers you can find with USB-A is 5V/3A for Qualcomm QuickCharge and that one also downgrades to 500mA (iirc) if the requesting device doesn't provide the correct signaling.

There is NO signalling by normal clients on USB-A. The host doesn't downgrade as such. The client decides how much current can be drawn based on the voltage/resistances on the D- and D+ pins, used for the data transfer. That's why to ensure you get 2A on an Apple thing, you need an Apple host port or charger, or one that's 100% compatible.

A gadget using the "Qualcomm QuickCharge" spec likely only takes 3A from a 100% compliant Qualcomm QuickCharge host. It doesn't seem to be in any actual proper USB standard, so I've no idea if the Qualcomm QuickCharge host will deliver 3A to a dumb load. Certainly ORDINARY USB -A hosts and chargers are supposed to simply supply UP TO their rated spec to a dumb load and shut down till disconnected if excess current is taken as that would be a fault condition. Actual gadgets are supposed to be cautious and only take 0.1A or 0.5A (often only 0.1) if the SW/HW in the gadget can't figure the D- and D+ line conditions. That sensing is done before negotiation of device class, if any.
There are loads of "dumb" things you can plug into USB ports. Most don't check anything and assume 500mA is OK. A 30W audio amp that claims to run on 5V @ 500mA is an amusing piece of marketing nonsense. Class AB would give maybe 75% of 2.5W, both channels, = 3.75W/2 = 1.875W per channel. Class D (basically a SMPSU modulated by audio) might manage 95%, or nearly 2.4W, 1.2W per channel.
Invent a fictitious PMPO and x2 because it's stereo? Or leave out the decimal point?