How long will the batteries actually last in a particular lock installed into a door? This can be determined by figuring out the number of times access is gained through the door. This can be the actual (or a rough guess) of how many times a year a particular lock will operate. Counters can be installed at the top of the door for a given period of time. Then multiply the number of days, weeks, etc. to come to one year.
Another option is to use a set of calculations to determine the average usage. High Traffic can be considered 100-200 openings per day; Medium Traffic can be considered 50 openings per day and Low Traffic (residential or limited operation) can be considered 25 openings per day.
To round out the traffic level numbers, the high, medium and low openings are for 365 days. Therefore, a 100- opening High Traffic door will have approximately 36,500 to 73,000 openings in a year. The Medium Traffic door will have 18,250 and the Low will have 9,125.
Using these numbers is a good way to gain an idea of the time a set of batteries will last in a particular lock once you know an average number of cycles. For example, according to Securitron, the six AA battery equipped SABL® has been tested for over 100,000 cycles, two year average battery life. Using 36,500 openings in a year provides a comfortable excess to insure two years of operation.
I have not included doors that are in very high usage such as a large department store, office/manufacturing facility or entry door for a commercial building as most of these doors are operated using high energy operators with sensors. For these applications, the number of openings will probably range from 1,000 cycles per day and up.
Note: The ANSI/BHMA Standard A156.2: Locks and Latches, Series 4000 Bored Lever Handle and Knob Sets Cycle Test for Grade 1 cylindrical locks is 800,000 cycles.
Most standalone, electromechanical door locks are powered using AA Alkaline batteries. A notable exception and possibly a look into the future is the Alarm Lock Networx Lock. Alarm Lock has increased the battery size for the Networx Locks to operate using four “C” alkaline batteries. As a result, the Alarm Lock Networx locks have a stated five-year plus battery life.
OK, so what about the batteries themselves? When we purchase batteries, is there a particular company you prefer? There are Eveready, Energizer, Ray-O-Vac, Duracell to name a few, as well as custom brands including Sanyo, Maxwell or Motorola. Most brands have reasonable quality batteries.
Most alkaline batteries are considered dead when the voltage drops from fully charged at ~ 1.5 volts to 0.8 volts.
Choosing The Right Battery
All batteries are not the same. They vary by manufacturer, models and individual batteries. AA alkaline batteries are the recommended battery power for most electromechanical locks. Alkaline batteries, developed in the 1950s, have a higher energy density and a longer shelf life than the standard or heavy duty batteries. The difference between standard, alkaline and lithium batteries is the composition and the way the stored chemical energy is converted into electrical energy.
Points to consider:
- Batteries (cells) still in their packaging can lose upwards of 10 percent of their original charge every year. Some battery packages have a date stamp.
- Putting batteries in the refrigerator or freezer can slow this discharge rate. Not all batteries operate properly after they are frozen.
- Do not install a refrigerated (cold) battery until it is warmed to room temperature.
- When replacing batteries, make sure that all of the batteries are the same type, strength and age. Do not mix alkaline and nickel oxide or any other batteries. Batteries that have been on the shelf for more than one year should not be mixed with new batteries or used batteries in a lock.
- Do not mix rechargeable batteries with non-rechargeable batteries as rechargeable batteries have less voltage (approximately 1.2 volts instead of 1.5 volts).
- Do not use rechargeable batteries in electromechanical locks unless approved by the lock manufacturer. The lower (fully charged) voltage may cause problems as a four battery lock will have only 4-8 volts instead of 6 volts.
- Batteries wear out faster in warmer climates or if the lock is installed onto a hollow metal door facing east.