You don't want the charger inside the battery. The basic law is "If It's Mains, It's Big". A better solution would be a wall-wart adaptor for recharging and a socket to connect to the charger.

Problem is though that rechargeable batteries *all* self-discharge. That means that you'll always need to recharge before a gig, else there might not be enough juice in the battery next time you pick up the instrument. Or worse, there might be enough to run during the soundcheck, but it'll die halfway through the second song.

There's also the further problem of what to do if you *do* forget to change the battery. At the moment, you can just swap it out. But if your battery is sealed inside the guitar, you'll be unable to use the guitar until you've recharged it, which will be just peachy when you realise too late that you've forgotten.

To be honest, I don't think anyone would pay for batteries sealed in the guitar. More likely is that people would pay for better quality battery holders. My Crafter (which is a cheap plywood job I got second-hand 12 years ago) has a PP3 battery holder which doesn't use a clip - instead it's spring-loaded to press the battery against the contacts. But some instrument makers still use old-style battery clips to save money, and some people still buy instruments with them because they're cheaper... :-/

The *real* solution to your problem is to buy a better battery housing and replace the one on your guitar. I should think Farnell or Rapid Electronics would have them - worth a check.

Graham.