may i ask where u intend to go with this alarm system 20 °C ?!
Well, there are two variations of this system. The existing one is for indoor conditions and its counterpart is for the automotive setting. To cover all the climates in this region, it needs to tolerate -20C for hours at a time (worst case). This battery is used when external power is removed or sabotaged, so it absolutely, positively must be self-contained.
Optikon said:
Is the battery your only power source for your design? If it is NOT, consider warming the battery. A low cost temperature controller can be made to warm the battery if the ambient gets too cold. This way you dont have to buy some exotic (read expensive) grade battery.
Okay this sounds like a good strategy. I have at least one lead acid cell that can fit the spec without major changes to the system. Perhaps I could use some kind of a thermister to activate this heater in a certain temperature range. What is a good method for this kind of low-power heating (special wire?)