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 MobileRead Forums PRS-T2 Are there power charger spec limits?

 11-24-2020, 04:08 AM #1 DoctorM Groupie   Posts: 159 Karma: 43000 Join Date: Mar 2010 Device: none Are there power charger spec limits? I've recently gotten a power outlet USB charger adapter that is 5V/3A. I know the T2 came with a 5V/1A adapter. Does the extra amperage pose a danger or does the reader only draw what it needs? I've seen different explanations on the net with regard to different devices, but it would be nice to be sure.
 11-24-2020, 08:07 AM #2 JSWolf Resident Curmudgeon     Posts: 61,402 Karma: 84262626 Join Date: Nov 2006 Location: Roslindale, Massachusetts Device: Kobo Aura H2O, PRS-650, PRS-T1, nook STR, iPad 4, iPhone SE 2020, PW3 5V/3A will work no problem with your T2.
 11-24-2020, 12:48 PM #3 hobnail Running with scissors   Posts: 948 Karma: 5500108 Join Date: Nov 2019 Device: none I asked this question on an electronics forum on reddit and the answer was that only the voltage matters. The higher amps mean that the device can use more of the electricity (meaning charge more quickly), if it's capable of it, but it's not a problem.
 11-24-2020, 06:19 PM #4 DoctorM Groupie   Posts: 159 Karma: 43000 Join Date: Mar 2010 Device: none Years ago I had someone at Radio Shack (if you remember those) tell me the opposite. That an adapter's amperage was more important than voltage. For example a device that runs on 8 D-batteries, which should be 12V can run just fine on 10V if the amperage is high enough. Maybe lower voltage is fine since batteries lose voltage over time, but higher is dangerous? What is troubling is that the adapter has a list something like this: 5V : 3A 7.5V : 2A 15V : 1A From a wattage standpoint that makes sense since Power (Watts) = Voltage x Current. But does that mean a reader drawing 1A is getting 15V? That seems like an issue.
11-24-2020, 06:47 PM   #5
pazos
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Quote:
 Originally Posted by DoctorM Years ago I had someone at Radio Shack (if you remember those) tell me the opposite. That an adapter's amperage was more important than voltage. For example a device that runs on 8 D-batteries, which should be 12V can run just fine on 10V if the amperage is high enough. Maybe lower voltage is fine since batteries lose voltage over time, but higher is dangerous? What is troubling is that the adapter has a list something like this: 5V : 3A 7.5V : 2A 15V : 1A From a wattage standpoint that makes sense since Power (Watts) = Voltage x Current. But does that mean a reader drawing 1A is getting 15V? That seems like an issue.
USB specs are 5V, 500mA.

More voltage might kill your device (allowed voltages are usually from 4.x to 5.x but better safe than sorry)

More current won't kill your device because it is your device the one that draws current.

If the adapter comes with a knob to change voltage then it is regulable by the user and will use the voltage you setup. If not and it is a "normal" mains to usb adapter you'll get 5v (up to 3A) unless the power circuit of the device you're going to charge negotiates for more voltage.

In all the cases the specs of your charger is: xV (up to yA) and the one that decides the amperage is your device, not your charger.

 12-04-2020, 06:28 AM #6 Ghitulescu Fanatic   Posts: 521 Karma: 400000 Join Date: Aug 2014 Device: PRS-T1 No charger is ever 5V, high amperage ones can easily go over 26V. I think Sony series is 5V/500mA. While no device ever lets the charger charge directly the batteries (thus a misnomer ), for safety reasons, using a much much higher amperage charger would destroy the electronics in the Sony if it's not provided with safety measures against higher voltages.
 12-04-2020, 09:06 PM #7 DoctorM Groupie   Posts: 159 Karma: 43000 Join Date: Mar 2010 Device: none Tested this for the first time yesterday. The charge icon came up, but when I returned the unit had not charges and I got a pop-up saying that. I didn't have time to see if it was a cable issue or what, so I just plugged directly into my PC and charged off the port. I'll try again later, but I wonder if the T2 stopped the charge to protect itself.
 12-04-2020, 11:33 PM #8 rkomar Wizard   Posts: 2,775 Karma: 11600001 Join Date: Oct 2010 Location: Sudbury, ON, Canada Device: PRS-505, PB 902, PRS-T1, PB 623, PB 840, PB 633 A trick I used with my PRS-505 when it was dead was to charge it a few hours, unplug it and then power it up. Once it had booted, I would plug it in to charge fully. For safety, the current to a powered down device is very low. It takes a long time to charge in that state. Booting it up allows the hardware to negotiate a higher current during charging, speeding up the process.
 12-05-2020, 01:45 AM #9 DoctorM Groupie   Posts: 159 Karma: 43000 Join Date: Mar 2010 Device: none The PRS-T1 & 2 readers boot up when you connect power to them.
 12-05-2020, 01:02 PM #10 rkomar Wizard   Posts: 2,775 Karma: 11600001 Join Date: Oct 2010 Location: Sudbury, ON, Canada Device: PRS-505, PB 902, PRS-T1, PB 623, PB 840, PB 633 I was talking about the situation where the battery has no charge and can't even boot the device. If yours can boot up but does not hold a charge, then the battery probably needs to be replaced.
12-07-2020, 01:03 PM   #11
Ghitulescu
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Quote:
 Originally Posted by DoctorM Tested this for the first time yesterday. The charge icon came up, but when I returned the unit had not charges and I got a pop-up saying that.
These are very picky units.
I have a few Sony cellphones and all three T series, and I don't remember which charger is which and mixed up with others, cables and chargers, Samsung, Nokia, Panasonic, nonames etc. Some work, some don't. Some can only charge, some do both.

I think the "true" 3A chargers have a recognition resistor (it's in the device) so it knows that the device can accept 0.5, 1, 2, 2.1 or 3A. It may be that cheap chargers do not react to this and pump all the juice, raising the voltage if the device resists the amperage.

Anyway, it's always better to charge with a lower amperage than with full, even if it takes longer. What are nights for?