Power supplies, backup power supply Security device 18.07.2022 15:07 18.07.2022 15:07

The example provides an approximate calculation of the required battery capacity for backup power supply of the basic Foxtrot module.

The typical power consumption of the CP-2005 basic module, with the relays open, is approx. 3W (each closed relay adds approx. 0.2W).

The quiescent power of the LTE part of the CP is approx. 0.1 W, the peak maximum power during transmission is 10 W (usually only around 2 ÷ 4 W, but in extreme cases up to 10 W for a short time).

With the estimated LTE activity (5 messages sent per hour, a total of max. 10 s of activity), the percentage time of LTE operation comes to about 3%.

The connection of the DC/DC converter with the power supply and the accumulator is presented in this article.


Tab. 1. calculation of the required battery capacity

module active peak percentage utilization   consumption in 24 hours:
LTE část 0,10 W 10,00 W     3,00%   10 Wh
CP-2005 bez LTE 3,00 W       100,00%   72 Wh
            total consumption in 24 hours 82 Wh
            capacity 24 V battery 3,4 Ah
            capacity 12 V accumulator 6,8 Ah
            converter efficiency 12/24 V (DDR-15G-24) 85 %
            resulting capacity 12 V accumulator 8,0 Ah


  1. the data in the table are informative, they are based on typical power consumption values and times, the example shows approximate times and backup battery requirements
  2. The actual backup time is also affected by ambient temperature, aging effects, etc.