Doorbell systems can communicate wirelessly with remotely located computing devices such as smartphones, laptops, gaming consoles, and streaming media players. In some embodiments, doorbells comprise a camera, a speaker, and a first battery. In several embodiments, a battery pack comprises a second battery and is electrically coupled to the doorbell. A battery charging system can electrically couple the second battery to the first battery such that the second battery is configured to recharge the first battery.