Charger for a Kindle

[markcomp]

First of all, apologies for this first post from someone who last studied physics 38 yrs ago
I have just bought my son's a Kindle each in the hope it will encourage them to read - it does, so far so good.
I charge them from the pc/laptop etc but an additional charger would seem a useful idea esp on holiday. As I already object to the waste (and cost) of having to buy a charger everytime I buy a new phone, I looked at the charging rate for the kindle: 5.25 volts max 500mA. My LG phone charger is 5.1 volts and 0.7A (700mA?).
Am I correct in assuming that the LG charger (same fitting as kindle) will only output what is drawn from it, i.e. the kindle will draw the current it needs ratehr than receive 700mA.
Am I going to do any harm?
Sorry if I am showing a degree of ignorance over modern chargers - when i studied chargers they were heavy steel cores and lots of copper wire!!!
Thanks

 

[(*steve*)]

You are correct in your assumption. Your memory from 38 years ago is excellent (I'm only 5 years behind you in "years since I did physics", so I'm not making fun of you)

 

[markcomp]

Thanks steve, I am glad I have found this forum, (although it was just for the kindle question originally) especially as am trying to look at integrating my solar hot water / boiler / heat exchanger which all do great things in their own way, but getting them to talk to each other is another matter - I am developing a healthy respect for heating engineers and the associated electronics!

 

[peter.mitchell]

Additonally, the resistance between data +/- will need to suit the kindle to put it into charge mode, it is likely it will, it is usually a standard of 0-120 ohms.

 

[markcomp]

Thanks Peter, i am afraid i do not know what "the resistance between data +/-" means exactly - time for a little googling! But I tried it and it seems to work. I did try it for two separate periods of half an hour to see if the batteries got warm but it all seems OK and certainly faster than via the USB on my PC.
I appreciate everyones time.
Thanks again

 

[(*steve*)]

If it's charging, then it must be OK

 

[peter.mitchell]

They both use a usb type connector for charging and data, the device detects whether it is plugged into a pc for data or plugged into a charger for power based on the pins in the usb plug, because as you have demonstrated, a charger will generally be able to provide more power through its plug.

The device will generally only draw as much current (amps)as it needs because it has an intelligent charge circuit, so if you use an ipad charger (2500mA) with a kindle (500mA) it will generally be fine, however, often it may charge slightly faster because it can charge the battery at 500mA AND power the device.