[thenextstopwillbe]

My relatively new MacBook will not start on battery power any longer. The light on the front comes on solid(not flashing) after pushing power button and i can hear the DVD drive spin up, then nothing. No display, no hard drive spinning, just dead. The only way I can clear the lockup is plug in ac adapter then hold power button for 5-10 seconds. The light goes out then I can power up normally. The battery is fully charged and I've tried resetting the SMC following Apple's instructions all to no avail. Any thoughts?

[Simon]

What happens if you unplug power after booting? Immediate shutdown?

[thenextstopwillbe]

it stays on and works normally. i haven't tested it recently but i think if i then put it to sleep on battery power and try to wake it then it won't come back on. it acts the same as if starting from powered off and turning on from battery power.

[Simon]

Boot with the charger connected. Then disconnect and let it run the battery down completely until the MB shuts off. Let it stay off for about five hours. Then connect the charger and let it charge the battery. Keep it connected over night. Check that all battery LEDs are on. Then disconnect the charger and try to boot. What happens?

[thenextstopwillbe]

thanks, i'll try it this weekend and let you know the results. i haven't run the battery down since getting the macbook so maybe it'll work. it's pretty much always on the charger and only very occasionally on battery for short periods.

[thenextstopwillbe]

tried your solution and it didn't work

i decided to uninstall startupsound.prefpane just in case it might be the problem. guess what? it was. everything seems to be working normally now. starts from battery and wakes from sleep on battery. glad i finally solved the mystery. thanks for your help just the same.