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battery capacity is 2xAA because of boost converter

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Glyn Hudson 2016-10-04 18:32:15 +01:00
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docs/power_consumption.md
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@ -12,7 +12,7 @@ Here is a scope trace illustrating the emonTH power consumption during a sensor
1. Atmega328 wakes up, starts sensors and takes readings: 17.5ms @ 8.4mA
2. Atmega328 goes back to watchdog sleep but leaves SPI initialised waiting for wait for RFM to initialise: 100ms @ 2mA
2. Atmega328 goes back to watchdog sleep but leaves SPI initialised waiting for wait for RFM to initialise: 100ms @ 2mA - \*now reduced ([see code](https://github.com/openenergymonitor/emonth2/blob/master/firmware/src/src.ino#L331))
3. RFM69CW transmission: 4ms @ 44mA
@ -37,19 +37,25 @@ To summarise:
- Off current = 0.06mA
- Off time = 59774.5 ms
[Oregon Embedded online battery life calculator tool](http://oregonembedded.com/batterycalc.htm) can now be used to calculate battery live. Assuming using 2 x AA alkaline batteries @ 2700 mAhr each = 5400
[Oregon Embedded online battery life calculator tool](http://oregonembedded.com/batterycalc.htm) can now be used to calculate battery live. Assuming using 2 x AA alkaline batteries @ 2700 mAhr each = 5400\*
\* *The 2 x AA batteries are connected in series but since uses emonTH uses a DC-DC converter capacity is effectivly 2xAA capacity (mius losses), [see forum post](https://community.openenergymonitor.org/t/emonth-v2/1696/18?u=glyn.hudson)*
![emonth V2 estimated battery life](emonth2_batterylife_estimate.png)
Given the measured power consumption the emonTh2 is estimated to have a battery life of 7.6 years!
Plugging in the [power consumption figures from the emonTh V1](http://blog.openenergymonitor.org/2013/10/emonth-update-software-power/) (with DHT22) into the calculator a 1.4 year battery life is estimated.
Plugging in the [power consumption figures from the emonTh V1](http://blog.openenergymonitor.org/2013/10/emonth-update-software-power/) (with DHT22) into the calculator a 1.4 year battery life is estimated.
![emonth V1 estimated battery life](emonth_V1_estimated_batterylife.png)
From [real world testing](http://blog.openenergymonitor.org/2015/02/real-world-emonth-battery-life) is been established that the emonTh V1 actually achieves a 8 month battery life. This is 57% less than the estimated figure.
Assuming the battery life calculator is overestimating by the same amount for the emonTH V2 we can **expect a real world battery life of just over 5 years**, which is not too bad :-p
Assuming the battery life calculator is overestimating by the same amount for the emonTH V2 we can **expect a real world battery life of just over 5 years**, which is not too bad :-p
I have setup a battery life test with the emonTh V2 with Si7021 sensor, I will report back in a couple of years :-)
***
See [forum topic discussion](https://community.openenergymonitor.org/t/emonth-v2/1696/18)