Safe voltage for battery modules


#1

What voltage can be considered safe for Kits powered by mini or standard battery modules? For the case where an outage is not acceptable so the batteries have to replaced in good time.

Any experiences or expectations for the standard kits?

Push Button Kit
Climate Monitor Kit
Motion Detector Kit
Flood Detector Kit
LCD Thermostat Kit

CO2 Monitor Kit


How to know that battery is needed to be replaced?
#2

Hi,
did you mean minimal voltage?

It depends on the module. E.g.: core has (according to specification), minimal operating voltage 2V.

* Operating voltage range: 2.0 V to 3.6 V

Of course some modules needs higher voltage. E.g. CO2, LCD. So it depends on sets of modules you are using.


#3

yes, the minimum voltage. Or to be more precise, searching for the really safe moment when to replace the batteries. For example, with CO2 module I can see in the measurement history that when the voltage reached 3,2V then it was very fast, within 6 hours the voltage was below 3 and it was disconnected from the network. In this case, I would consider 3,5V as such safe value.

I know there are more factors, the batteries can vary, the temperature can be also the factor, so probably I have to collect my own data, analyze and then set some alerts.


#4

Hi, it’s little bit more complex.

For AAA Alkaline or NiMh battery cell you can follow this rule: When the battery voltage is is under 1.2 V it is almost empty (good time to replace it). When battery voltage is under 1.0 V it it is completely dead. And it is nod good condition for some types of Alkaline cells (like Duracell, Varta is better), it can cause electrolyte leak.

About minimal voltage for BigClown Modules using Mini Battery and Battery Modules:

Mini Battery Module (2 x AA) is equipped with Step Up regulator, regulating output voltage to 3.1V When the voltage of two AAA batteries falls under this voltage, it can still boost it to 3.1V and all modules will works fine. Theoretically the minimum input voltage is 0.7 V (0.35 V per cell ). But when the battery cell has les than 1.0 V the voltage falls very rapidly after load.

Battery Module (4 x AAA) is equipped with Step Down regulator regulating output voltage to 3.1 V. When the voltage is less than 3.2V (0.8 V per cell) the regulator disconnect the output. It matches your comment.

In booth cases Battery or Mini Battery module, battery cells under 1.0 V is not stable condition, and it can cause for example reset of MCU during measuring CO2 or turning on LED on Core module :slight_smile:


#5

Practical example with long usage of module (about 6 months) :
module (green colors in graph) : 4x sensors (tags) + 1x CO2 - standard battery module 4x 1.5V
About 14 days to change battery when reach limit about 4.0V (i think it is safe limit - change battery)
About 2 days only to change battery when limit 3.5V
… when change batery - immediatelly about 6.5V


#6


Second battery change another node …


#7

and for Battery Mini