Quote:
Originally Posted by Ardjan
I have just read this thread and all the doubts about voltages and chargers and thought it might be good to try to explain how this works. First of all as mentioned before 5V is the USB standard, so all generic USB chargers should be fine. The reason the Sony Reader is specified for 3.7V is that it is probably using a Li-Ion battery.
The Sony Reader has some circuitry build-in that handles the charging of this 3.7V battery with the 5V input, this type of circuitry also prevents over-charging, so I'm convinced that it is safe to keep the reader connected to the charger for longer periods (personally I charge the reader overnight).
The mentioned rating of 940mA for the Sony Reader should probably be 940mAh which is a rating of the capacity of the battery and cannot be compared to the mA rating of the charger. A PC's USB port can output 500mA at most, so any charger rated for more than 500mA should be fine to charge the Sony Reader I guess.
Personally I use the carger of my mobile phone for my reader and this works just fine. I prefer this to charging using my computer because a computer USB port can switch from power mode causing the charging to start and stop. Since Li-Ion batteries have a limited number of charge cycles interrupting the charging process frequently reduces the life time of the battery (although this effect is probably not very big).
On hindsight this post is a bit rich on technical details (especially since this is my first post on mobileread  ), so let me summarize: All generic 5V USB chargers with a rating of at least 500mA should be fine for charging the Sony Readers. Leaving the reader in the charger after the light has gone out shouldn't do any damage as far as I can see.
I hope this was helpful. |
Welcome to MR, Ardjan. Very useful information.