The longest battery life for the dedicated products in our review is the Levana Lila, which ran for 12.75 hours in full use mode. The manufacturer claims this unit will work up to 72 hours in power saving mode, but we only tested the monitors in full use. The Infant Optics DXR-8 came in second place with a shorter run time of closer to 11.5 hours. The Motorola MBP36S earned the lowest score for battery life with a runtime just under 7 hours. While not necessarily a deal breaker, there are plenty of other reasons to dislike the Motorola MBP36S, and the battery life is just a small part of a disappointing overall picture (no pun intended).
Think about the size of your home and your daily routine when deciding which brand/model to buy. If you'll be making calls during nap time, for example, look for monitors with lights that let you know when your baby is awake. Of course you can accomplish the same thing by turning down the sound on a video monitor, but lights are more likely to catch your eye.
Battery: We wanted a monitor battery that could last overnight, or at least eight hours, without being plugged in. We thought the ideal product would automatically cut off an idle display screen to conserve battery, work at least a few hours unplugged with the screen on, and recharge fairly efficiently. We made a rechargeable battery a requirement. We preferred units designed to connect to power via a standard USB connector, and looked for reports that the baby monitors could reliably charge, recharge, and hold a charge long-term—a disappointingly rare ability in baby monitors.