At last I had the time to open it.  

I have another idea, why not use the empty batterybay for another battery and connect them in parallel? double the running time. What do you think?

What about battery life???!!! Maybe it is also important (X5 <10 hours) I do not think it is "advisable" to give advice about something you did not compare to, maybe he will like the Sony A17 better.   I learned my lesson, and will never like or dislike a DAP without trying it myself...

Here he talks about  it compared to the X5 :   http://www.3dnews.ru/903427   https://translate.google.com/translate?sl=ru&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=http%3A%2F%2Fwww.3dnews.ru%2F903427&edit-text=

....pricejapan.com confirmed that the menu can be changed to English.

    Some time ago, I asked my Malaysian friend who works at a Sony factory to forward  some letters to Sony executives and engineers (any in top management), where I emphasized the importance of battery life and microsd to us and gave them the J3 as an example (50+ hours), and what perfect dap...

    Also I like to remind you that batteries need  at lease 3-5 charges before they give their full potential.

OK, did you try a different USB charger (with different Amp) ?   Could the higher mah be the reason?

That is great!   I was not expecting it to be thicker!!!??? Please update us. And Congrats for saving it and us

    Its a gamble, and I hope all works for you.     As much as I want to go and try it, I am afraid to ruin mine .     Maybe you got bigger .........

    I was expecting this.   Please keep us updated with your finding.   I do not think it will be that much difficult to solder.   Just practice on something other than the battery ......

Do you know if the menus are in English?

All the batteries I found where always bigger than what the compartment can fit.   Nice finding.

I do remember finding batteries with the above specs , but all wont fit! Good hunting