This will make your AAA batteries recharge while the player is plugged on the USB port. Do this only if you use rechargable batteries, using the player with normal batteries and this mod could end up with explosions, etc.
Because the NiMH batteries are relatively new, they aren't yet as robust as older NiCd batteries, and NiMH batteries produce Hydrogen gas when overcharged. Improper charging (such as unmanaged charging through USB ports) has the potential to blow up the batteries.
Now don't think any hollywood big fiery blast explosions, more like a "poof" with lots of icky battery fluid splashing all over the place.
To prevent damage to you, your player, and your battery, DO NOT CHARGE IT WITH THE PLAYER
(ignoring the fact that ordinary (non-internal battery) players do not have the proper connections to pump USB power through the battery.)
The author of the idea, thought, defends it, arguing:
- that the final measured current is 70~100mAh
- that he has been using it for an year without any problem
- that we already left it charging 18 hours, and, still, no problems
- that the USB ports got current limitators, and, in most cases, microfuses next to it
After all, only do this if you KNOW what you are doing.
What you will need
- 3 IN4148 diodes, the smaller, the better
- Plastic Tubing("Spaguetti")(Heat shrink tube from Electronics Hobby stores
How to do it
Connect the three diodes in series, put then inside the spaguetti and host them somewhere on the player. The place where the flat brown cable is used to be nice place to host the diodes. Then wire the anode extremity to the +5V pin of the USB port, and the cathode to the Positive(+) side of the battery.
How does it work
The USB supply voltage is 5.0V. The current to charge the baterry must be between 60~70 mA.
Using three diodes, it's better, because each one drops 0.6V. The total drop will be of 1.8V. This will reduce the heating.
*Elias Tapxure Netto - Sao Paulo -Brasil
I think also you may use 5v to 3v and 3v to 1.5v regulators (like 3pin smd transistor). 5v to 3v regulator marked 662S. 3 to 1.5v regulator marked 65EL. these are keeps right voltage and keeps power good as input. if you want to create 1.5v for battery, you have to use both of regulators and use resistor 2.5 Ohm and Diode.
*Nagendra Pratap Singh - Auckland, New Zealand
Author 2 (From New Zealand). I used a similar diagram but with 5 diodes and a 22ohm half watt resistor. This works very well and gives a floating voltage of 2.2 v and a charging current of 39ma. I use a car FM transmitter to listen to this mp3/wma player.My car FM transmitter has 4 USB ports output which I use to charge this and also charge my Mobile phone. The car output is like 5.8v so the current there becomes like 75ma. I also use a resistor which can be seen in the photo.
+5 v ----------|>--|>--|>--|>--|>-----/\/\/\/\/------+ve end Battery -ve end --
From USB D1 D2 D3 D4 D5 Resistor