Conclusion: It is critical that if using the FACP to provide primary power to the AES radio, you allocate 6 amp hours of the FACP battery bank to the FIRE radio.
Here is why:
AES Fire Radios used by Security Solutions NW are recommended by AES to use a 12 Amp/hr battery. The graphic below illustrates the power consumption based on a 12-volt battery.
When powering the AES radio from the FACP you need to calculate the current draw expected at 24 volts and adjust the FACP batteries to accommodate the AES Fire Radio.
Since all the AES values are based on a 12-volt battery, we can easily deduce that at 24 volts the amp-hour is 1/2 the 12-volt value.
Standby Current (amps) .400 x 12 volts = 4.8 Watts. 4.8 Watts / 24 volts = .200 amps @ 24 volts.
Alarm Transmit Current (amps) 1.55 x 12 = 18.6 Watts. 18.6 Watts / 24 Volts = .775 amps @ 24 volts.
24 Hours standby @ .200 amps = 4.8 amp hour + (Alarm transmit current .775 X .25 (15 minutes) = .193 Amp hour) = 5 Amp Hour @ 24 volts.
AES uses a safety factor of 120%. 5 amp hour x 120% = 6 amp hour.
Even though the AES radio has its own backup battery, the AES Fire Radio will affect the FACP backup battery bank by using 6 Amp hours of the FACP battery bank. Then when the FACP batteries are depleted, the AES radio battery will continue to operate the AES radio. However, the FACP is no longer functional.
It is critical that if using the FACP to provide primary power to the AES radio, you allocate 6 amp hours of the FACP battery bank to the FIRE radio.