I'm looking to shoot a time lapse with my Olympus OMD E-M10 and I was wondering it it is possible to use an external power source. Standard battery life isn't too good on this camera; it only takes about 300 shots on one charge.
Olympus doesn't make an AC adapter for this camera. (They do / did for higher-end models.)
However, there is another option: a third party "fake battery" which actually connects to a power source. Fujifilm actually makes an official one for their cameras (they call it a "DC coupler"). I'm not aware of any off-the-shelf commercial solution to fit the E-M10, but hardware hobbyist Helge Suess will apparently make you one on demand.
(It probably goes without saying that this will likely void your warranty.)