If you’re like me, and you own a (now discontinued) Microtrack 24/96 portable digital recorder, and your battery life is terrible, here’s a tip: buy a replacement iPhone battery. Reports on the M-Audio forums indicate good results:
Works even much longer: I’ve got 3 hours 45 minutes for the continuos record (mp3, to keep recording longer for test), Phantom power ON, headphones in, backlit off. After that time battery had 3.5 Volts, which is perfect (3V minimum supposed for Li-Pol batteries), and then device switched off itself.
There’s even a decent step-by-step instruction guide here.