Hello!
I have an eMachines M5312 (crappy laptop, I know). It still works fine, except that it emits a high-pitched hum when I have the battery in. If I remove it and just use the power cord it is fine, but it's annoying to not have any battery power. I can hear that the sound is coming from the area around the battery, but I don't know if it is a problem with my battery or something with the internal power.
Any ideas?

Every M5312 we have seen with that high pitched howl failed soon afterwards... and was not repairable.
eMachines no longer makes laptops, I am told.
Good luck.

It is probably a wire wrapped inductor in the charging circuit that is making the noise. Probably indicatintg an impending catastrophic failure that Raybay mentions. Save your pennies for a new laptop and back up any important data while you can