Can anyone measure the voltage of the battery with a simple voltimeter-tester? DC.
Look for the battery that is mentioned here (US473850A8T) and is sold like 3.7 volts.
It is possible that it accepts voltages from 3.7 - 5.2 for charge , or the Sony has an internal stabilizer IC to reduce the voltage from the charger (5.2 volts).
All pages to buy this battery are in chinese with register.
Here Sony Li-Polymer [ 3.7V ] batteries :
I think is only to drop the yellow tape from PRS battery and sold 2 wires (red-black) with conector from old to new battery.
But the problem is to identify the correct model of battery and buy it in chinese.
Battery from PRS-505 may be not equal to the PRS-500 as I see in this photos :
I can read only US32xxxxxxH
And I cannot find none battery with similar reference.
Although may be the same as 500 with another manufacturer , ru ?
Measures from 500 are : (50mm x 37mm x 4.7mm)
Here batteries from sony clie 3.7 volts looks similar: