Let’s take you through the battery replacement process to help you do it safely and correctly. http://PrecisionDoor.net shows you how to change the battery in your Liftmaster remote and keypad. If incoming power is inadequate, regardless of battery … Check batteries disconnected: Disconnect batteries from the board, and meter the harness'. LiftMaster Battery Back Up; LiftMaster MyQ; LiftMaster Parking Assist; LiftMaster Disconnects; LiftMaster Other Accessories; LiftMaster Radio Controls . If a battery reads less than 11.5vdc sitting, replace the battery it will never fully recharge. New LiftMaster 485LM Battery Backup for Garage Door Openers 3840 3850 8360 8550. Each battery should read 12vdc individually. Disconnect the batteries from the main board and meter each battery for DC voltage. Batteries typically last around 2 … FREE Shipping. 4.8 out of 5 stars 11. It would be best if you replaced your backup battery every two years, but when its time for replacement, the opener will beep, and LED light will turn red to indicate. Each battery should read within 10% of 12v. Tip: It is also helpful to ask the age of the batteries. For maximum battery life and prevent damage, disconnect the battery when the garage door opener is unplugged for an extended period of time. How to change battery in a LiftMaster garage door opener. 34. In battery backup mode, the Automatic Garage Door Lock will unlock when the garage door is opened, and will remain disabled until power is restored. During a power outage the battery supplies power for up to 24 hours of operation. If either battery is lower than 11v, replace the battery; this will effect functionality of the gate operator. Checking and replacing your Ghost Controls gate opener system battery. $53.34 $ 53. LiftMaster 9 Switch 390 MHz ( Up to 1993) LiftMaster Green Learn Button (1993 - 1995) LiftMaster Red Learn Button (1996 - 2005) LiftMaster Purple Learn Button (2006 - Current) LiftMaster Yellow Learn Button (2011 - Current) Commercial.