Presenting: the Cowon infinityAudio 7

How do you fix a Cowon iAudio 7 with a busted LiPo battery (it actually had a hole in it) without an identical replacement, and retaining the spectacular battery life?

Like this:



(the ugly volume switches are part of another repair - the previous owner had broken the original ones and removed the plastic cover on top of them, so I just cut the button openings wide open and glued in standard TAC switches)

Those are two 2 amp-hour 18650 LiIon cells connected in parallel, giving an equivalent capacity of approximately 4 Ah. Considering that current draw while playing Ogg Vorbis is extremely small (about 25 mA), the big battery ought to be enough to run the player for almost a week - continuously! Hence the "infinity" in the name

And it's not that much bigger compared to the original; it's no longer easily pocketable in pants, but I never put my player in my pants pockets anyway, so it doesn't bother me.
It is, of course, a fair bit heavier (one 18650 weighs more than the stock player), but you can't have humongous battery life without paying anything.

Edit: in case it's puzzling you, the fourth picture is of the battery hooked up (via the red JST connector that you can see in the other pics) to my RC charger. The player retains the ability to charge via USB, but it takes eight hours to charge a 4Ah pack from the 500mA that's all that USB can provide, so I added the external option to speed things up.

Oh, and by the way, he ^^^ is the previous owner who busted the volume buttons.

I'm not new to this sort of insanity... er, I mean, mods :P but this is by far the most overkill in relation to actual battery life/current draw. A few others: one is the Zen in my signature, which got a single 18650; another is my phone, of which I lack a picture, which got - you guessed it - yet another 18650; and then my old (and now sadly dead for good) digicam, which got another AA to compensate for voltage regulation troubles. Oh, and my multimeter

My use of the player is too inconsistent to be able to tell precisely; but I've conducted extensive testing with my bench power supply before installing the big pack, and the theory is mathematically sound. Frankly though, I don't much care if it lasts five days or six or seven - all I know is that I can use it at will, and as long as I occasionally remember to hook it up to charge I'm set. And if I forget, well, I can always throw a few hours of playing time in it via USB...
Actually, I've been using it for most of today as an audio source for my stereo. With the big pack, the worry of connecting it to an external power supply in order to not find it dead when I go out later goes out the window.

The more I use it, the more I like it.

On this subject... I've no intention to set foot in american soil anytime soon, so I should be able to avoid most of the carry-it-onboard-and-die paranoia, but in march I'm headed to Finland for a few days (I live in Italy), and I'd very much like to carry the frankensteinized player with me.
What do you think is the best way of dealing with the issue: finding some sort of casing for the battery and hoping they don't see any problem to speak of, knowing that if they do they'll cause me no end of grief, or just going up to them and saying "hey, I have this music player that I modified, I already know it'll look suspicious in the x-ray machine, so I want to show you that all it is is in fact a music player", turn it on and make them listen to some music?

By the way, here are a few pics of the work-in-progress:


The 18650 pack being soldered together



Not yet completely glued in place, soldering on the wires to the player and to the charging connector



Contacts done, pack glued on the sides; I needed to glue it everywhere, but there was that empty space there. I could have just put a big glop of melt glue in there, but I wanted to be able to take it apart again if need be without leaving half a ton of glue on the circuits, so...



...I put thin stripes of styrofoam in the empty spaces...



...and then glued everything together.


I've also uploaded another pic of how the player looks; I added it to the first post.

...huh?