ELK M1 Low Battery

I purchased my system in 2011 and today I'm seeing a Low Battery indication on the keypad screen.  Should I expect just a few years service from the backup battery on the M1?  If all I have to do is replace it to remove the message, does anyone have a suggestion where the best place is to buy a replacement?

Looks like, all you need just battery replacement.

Its probably smart to replace the battery every two years. By the time you get a message on the console, the battery is pretty gone.

Normal lifetime for a SLA battery is 3-5 years, so yours is right on schedule.
 
I have had good experiences with Power Sonic batteries.  The M1's original battery is a 8 Ah battery, but you can replace it with a 9 Ah battery
which is the same physical size, and will give you a little extra standby time.
 
Note that batteries are available with connectors of 2 different sizes, F1 and F2.  The M1 uses F1 connectors
 
9 Ah: www.amazon.com/dp/B00FA602DY
8 Ah: www.amazon.com/dp/B00FA602DY/

Here is a good resource for replacement batteries. http://www.lowvoltagesupply.com/category-s/1824.htm