Normally, I just use my felt-lined charging cradle as a PDA stand, and plug into the wall if the piano is near an outlet. If there is no outlet, I have a spare battery for my Dell, just like Ron's. Unfortunately, the only way to get "big" battery life from a PDA is with a big battery. I just ordered one of these: http://www.batterymart.com/p-powerbase-external-battery-pack-us-ac-adapter.html To use this, you need the 12V car charger accessory for your PDA. This plugs into the external battery's output cord, which is basically a 12V cigarette lighter socket. The external battery plugs into the wall to charge overnight. This battery is big, but it's flat so it will fit nicely in a tool case. Line the bottom of it with felt so it can be placed on any surface, and you can tune all day without worrying about battery power or finding outlets.
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