Keyless entry battery backup

ACCESS CONTROL INFORMATION

Know how long your maglock doors will stay locked after a power outage happens.

If you have your access control system through a different company contact them to find out this information rather than waiting for a power outage to happen.

Typical battery backup holds a door for 3 hours or less. If you need more contact your security contractor for a quote.

I did an example calculation for one door with 2 maglocks, one reader, one request to exit motion and one request to exit button on a PDK controller with 2amps of power.

Example equipment list on one door:

2 Maglocks at 505mA each = 1010mA or 1 amp

Reader 100mA

RTE button 75-100 depending on light on the button etc...

RTE motion 50mA depending on model

Controller 100-150

Total current draw is 1410mA or 1.4 amps and the PDK controller has 2amps (The below numbers are figured using the SDCsecurity.com calculator using 1.5amps)

Typically, we put a 7amp hour battery as the backup battery and this will only hold the doors for about 3 hours. Without a specific access control specification this is the norm in the industry so when you need more then make sure you ask your alarm company to design the system to your specifications.

If anything else is going on like people reading their cards and people coming in and out the door then that 3 hours will be less.

To hold the door for 6 hours you would need a 12amp hour battery

To hold the door for 12 hours you need 21 amp hours of battery power

To hold the door for 24 hours you need a 36 amp hour battery (The PDK panel will charge the 36 amp hour battery or 2 - 18 amp hour batteries but it will take time)

To hold the door for 48 hours you need a 59 amp hour battery or a combination of batteries

Tol hold the door for 72 hours or over the weekend you will need an 80 amp hour battery or combination of batteries

Batteries need to be replaced every 3 to 5 years so when you replace them label them with the replacement date. If you are in an area like Park City Utah that has brown outs then your batteries may need to be replaced more often. Make sure when you do replace them to hook up the positive and negative in the exact way that it was before you took the batteries out so take a picture or even better just have your alarm company provide this service.

At the point after 24 hours of backup it may be best to consider putting these systems on your emergency backup generator if you have one or buy a UPS that is typically several thousand dollars because we would need battery cans and special charging circuits or larger power supplies if we put battery backup. Most power supplies have limits to how large of batteries they can charge. The PDK controllers can charge a 36 amp hour battery (Or 2 of the 18 amp hour batteries) although it will take quite a bit of time..

FYI the PDK power supply will only power 12 VDC locks not 24 VDC 

When it is possible I personally like to use Electronic Strikes because they allow free egress without any prior knowledge so someone inside does not need to know where the button is (hence the request to exit motion) and if there is a fire people can get out easily.

Many companies will tell you that you don’t need a request to exit motion if you have electronic door strikes and depending on what you want your system to accomplish you may not.

If you want to get a door forced open notification then you would need both a door status switch (Door Contact) and a request to exit motion. When someone reads their card they enter and the door status switch opens and then closes. If someone forces the door open without a valid card read then you would get a door forced open as long as you have a request to exist motion. This allows people to leave and shunts the door switch but will notify you if someone come in.

Some of my customers tell me that they don’t need a security system because they have their keyless entry access control system.

If they have a power failure then their building is UNLOCKED if they have maglocks about 2 to 3 hours after the power loss. When they have a security system that system has battery backup and secures the building even if there is a power loss because when someone comes into the building the alarm will activate.

Some customers want us to set the system up to open their doors and disarm their system with one card read or when the first person presents their card rather than having to disarm with a code or with their smart phone.

This is not a prudent move because if someone finds a lost card in the parking lot or takes it from someone now they are in the building and the system is disarmed. It is best to keep this separate so you have to present your card or fob or Bluetooth on your phone and then you need to disarm the security system separately.

Most access control systems are not tied to a central station so you need a separate security system. If we install a combination DMP system we can do that.

Another thing that many companies don’t do is install door status switches (Contacts) so the access control system will open the door but if someone props the door open or forces it open nothing happens and if your access system is completely separate from your security system then you may have 2 door status switches, one for the access control system and one for the security system or a DPDT switch that connects to both although it is best to do 2 separate switches.

Another item to be aware of is ELECTRONIC DOOR STRIKES that do allow free egress come in different types. They can be FAIL SECURE which means they stay locked in the even of a power failure or they can be FAIL SAFE meaning that they unlock in the event of power failure so even with door strikes you still may want to increase your battery backup on the door power supplies or make sure they are FAIL SECURE strikes. I did one 6 story building where the fire marshal had me install fail safe strikes on all the outside doors so if there was a fire all the doors would release so firemen could get in from any side of the building without a key. Discuss these variables before the system is wired or installed so you get the proper equipment from the start.

Larry.Love@jci.com 801 898 6003