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Carbon monoxide alarm battery power consumption

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Modern battery power supply systems have struggled with power usage for a long time. In the initial design, estimating the battery capacity is a very difficult task. In fact, battery consumption is almost dependent on device performance, which includes hardware, firmware, features, and software. Today we will discuss the battery design for a Carbon Monoxide Alarm

1. Determining factors affecting the power consumption of carbon monoxide batteries

The consumption of battery power is mainly based on two factors: function and software.

Whether the carbon monoxide detector passes EN 50291 shall also be taken into account.

Function:

  • (1)Hardware: The sensor shall be the main hardware of the carbon monoxide alarm. In this section, I will discuss the power consumption of a typical CO sensor.  

Take Semiconductor CO Sensors as example. Assume loop voltage Vc=5V,VRL=5V, load resistance RL=10K。Rs =(Vc/VRL -1)*RL=8,So the power consumption of the sensor

These values are listed in the product manual. The sensor’s power consumption is absolute, but the specific power consumption is dependent on the peripheral circuit’s load.

Electrochemical CO Sensor:

Normal operating mode: 46.2 mW

Shut down mode: 3.3 µW

Sleep mode: 1.2 mW

The remaining 2 common sensors power consumption are as follows:  

Opto-Chemical CO Sensor:0.3 ~ 1W

Biomimetic CO Sensor: ≤2W

(2)Basic standard functions: low voltage alarm, sound and light alarm.

When the carbon monoxide alarm is in a low voltage state, the 85dB buzzer current (including the static current) of our products is 0.01412mah.

The power consumption of the sound alarm is slightly higher, 0.24 MA/min. While the power consumption of the LED is so low that it is negligible.

Of course, different products will have different working currents and quiescent currents.

If it meets EN:50291, the difference should be minimal. Excessive quiescent current can significantly reduce battery life.

Extra functions:EN50291 has additional functions. For example, LCD displays and product interconnectivity.

If we only consider the problem of power consumption, the backlight consumes 99 percent of the power consumed by the LCD.

So LCD power consumption is simple to calculate, typically based on the number of LED beads in the backlight. For example, a single LED consumes 15mA, three LEDs consume 45mA.

Product interconnectivity: If the requirements aren’t too stringent, we can simply calculate.

Zigbee: Sleep time consumption/day = 1.5uA * 24h = 0.036mAh

( Zigbee sends data every 20 minutes for one second each time ), then the total power consumption of a day is 12.036mah.

WiFi:This formula can be used to calculate the power consumption of WiFi when products are interconnected.

Sleep Power × Sleep Time + Active Power × Active Time = Total Energy

Example: Figure 1, it consumes approximately 5uA current while sleeping. It is ready to transmit, send data, and go back to sleep after waking up. This process takes only 2-3ms and raises the average current to 5mA.

We also need to know how the device instantly wakes up to send or collect data (see table 1 below).  

Assume the device sends data every two seconds and is powered by a 3V battery.

Since power = current x voltage, the energy formula would be:

3V x 0.005 mA x 2 seconds + 3V x 5mA x .003 seconds = 0.075mW•s per 2 seconds

24 hours, will consume:

0.075mW•s / 2 s x 3600 s/h x 24 hours = 3240 mW•s of energy

Convert to MWH (more commonly used units) :

3240 mW•s / 3600 seconds per hour =0.9 mWh per day

Convert to MAH:  

0.9mWh / 3V =0.3 mAh per day

TX CurrentTX DurationSleep CurrentRang(m)Throughput
BLE     5     0.03      1  10-100 Low-high
table 1

Z-Wave: Z-wave smart home products using AC power consume less than 1W in standby state, generally around 0.3W.

Software:In fact, artificial intelligence can be used to reduce the power consumption of battery.

For example, set a sleep mode for the product. In a certain period of time, the alarm will automatically enter hibernation if there is no action value. This will reduce the power consumption of other components, which in turn reduce the power consumption of the battery.  

Let me show you an example and you’ll know that auto sleep is really energy efficient.

In standby state, the current is 1mAh/month and the current is only 12mAh/year.

If there is no auto sleep mode, the operating current is assumed to be 50mAh/month, which consumes 60mAh/year.

2. Calculation of battery power consumption

Speaking of which, do you know how to calculate battery life?  The specific power consumption is mainly related to the capacity and load current of the product. 

Take the battery of carbon monoxide alarm as an example (passed EN:50291).  

Assume your battery has a capacity of 1208mAh, the annual static current is 68.95mah, and the minimum operating voltage is 2.55V (i.e. 1085mAh).

The battery allows 10 years of self-discharge at 1.096% per year.  

Other products’ battery life is estimated using the same formula.

To learn more about your product’s battery life, please contact us so that we can assist you in estimating it.

3. Several common carbon monoxide batteries

According to the data in the table and our experience, combined with the existing alarm design characteristics, you should choose the battery with small volume, large capacity and within your budget.

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