# Battery life

The battery life of a device depends on many factors and it is not easy to build a model that will precisely determine this time. Efento NB-IoT loggers battery life time is up to 10 years or 195,000 transmissions (standard battery pack: 3 x AA batteries, 6300 mAh).

The main factors affecting battery life are:

* **Signal quality** - the worse the signal quality, the greater the number of retransmissions is necessary to send data to the server. The number of retransmissions is represented by the ECL parameter and battery life is significantly reduced at higher ECL values ​​(1 or 2)
* **Transmission period** - the more frequent the transmissions, the shorter the battery life of the device. With brand new battery pack, the device should send data about 195 000 times (assumptions: room temperature, ECL = 0, 20 measurements / transmission, transmission period small enough to make 195,000 transmissions within 10 years)
* **Ambient temperature** - in lower temperatures the batteries discharge faster. Lithium-ion batteries used in Efento loggers should not operate beyond the range specified in the device's technical card

The table below presents expected battery life time and monthly data usage depending on the settings and signal conditions (ECL). The values below are values for a temperature and humidity logger.

{% hint style="warning" %}
**Efento recommends to treat the battery life time calculations indicatively, and always assume that the real battery life time will be shorter due to many factors, which could not be included in the model.**
{% endhint %}

| **Measurement interval \[min]** | **Transmission interval \[min]** | **ACK period (every N messages)** | **Bluetooth interface** | **Battery lifetime \[years]**\*\* | **Data usage(up + down)**\* |
| ------------------------------- | -------------------------------- | --------------------------------- | ----------------------- | --------------------------------- | --------------------------- |
| **ECL = 0**                     | **ECL = 1**                      | **ECL = 2**                       |                         |                                   |                             |
| 15                              | 60                               | 24                                | OFF                     | 11                                | 5.7                         |
| ON                              | 11                               | 2.3                               | 1.1                     |                                   |                             |
| 3                               | 30                               | 12                                | OFF                     | 11                                | 3.1                         |
| ON                              | 8.6                              | 1.7                               | 0.9                     |                                   |                             |
| 3                               | 180                              | 8                                 | OFF                     | 11                                | 9                           |
| ON                              | 11                               | 2.7                               | 1.3                     |                                   |                             |
| 5                               | 60                               | 1                                 | OFF                     | 9.8                               | 1.9                         |
| ON                              | 6.5                              | 1.3                               | 0.7                     |                                   |                             |
| 5                               | 60                               | 24                                | OFF                     | 11                                | 5.7                         |
| ON                              | 11                               | 2.3                               | 1.2                     |                                   |                             |

* Table above presents maximum uplink data usage.
* Due to a compression algorithm, real data uplink data may be up to 25% lower compared to the values from the table above
* Downlink data does not take into the account configuration changes sent to the logger from the server and FOTA updates

{% hint style="warning" %}
Battery consumption is indicative. Battery lifetime is affected by many factors including:

* temperature, in which the device operates
* signal conditions
* type of sensors installed in the device
* number of BLE connections (i.e. to download the data from devcie's memory)
* number of user / threshold triggered transmissions
* number of new configurations sent from the server to the logger
* number of network registrations (if device changes its location, resets, there are some network issues, device needs to register to the network again what consumes a lot of battery)
* number of FOTA updates (not included in the model)
* complex physics of Li-ion batteries (in the model a simplified calculation is used). Due to physical processes which happen in the battery, maximum battery life time is 11 years. After that time, the battery will discharge, even if it is not used
  {% endhint %}


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