Can I Use More Than One Battery Pack in a Honeywell L5210?

No, you cannot use more than one battery pack in a Honeywell L5210. This might be surprising considering that the system actually has two separate battery connector ports. But these are actually used for two different battery types. Only one battery pack can be safely used at a time.

When an alarm system loses is AC power source, it will switch over to its battery backup. This will allow it to send outbound communication signals at all times so that active monitoring service can be maintained. Some users might think that installing multiple backup batteries is a good idea so that the system can run longer on backup power. But using multiple backup batteries with an L5210 could actually damage the system.

The L5210 System actually includes two battery ports. The smaller battery port can support either a LYNX Standard Capacity Battery or a LYNX High Capacity Battery. The larger battery port can support a LYNX Super High Capacity Battery. One might think that they could simply use a standard or high capacity battery alongside a super high capacity battery by installing the two battery packs in separate ports. But that practice can result in serious problems.

On the L5210 board in the picture, the smaller battery connector is being used, while the larger battery connector is open:

Trying to use multiple batteries in an L5210 would result in multiple problems. For one, you would't be able to fit two battery packs inside the panel. One battery would be forced to remain outside. While some users might be okay with this, it certainly isn't best practice. The bigger issue is that it may cause longterm damage to the system's board. It can also prevent the panel from getting enough AC power, and an AC power loss condition might always be present.

To keep your system running as long as possible, the super-high capacity battery option should be used. The system can remain running for up to 24 hours with this as the backup power source. If a user needs a solution for longer power outages, they might consider getting a power generator. This will keep the system powered on for an extended period of time