The enDAQ sensors have an embedded Li-ion Polymer battery. Many factors go into the expected battery life of a given device as this article explains along with providing some ways to approximate the expected battery life. The sensors can have their battery life extended with different trigger settings and/or by powering while plugged into an external USB power source.
In this Article
Both of these batteries are rechargeable Lithium-Ion Polymer.
Configuration Specific Battery Life Estimator
We have built a tool to estimate battery life depending on configuration and battery capacity (to estimate life by using a larger power supply).
Please note that this tool is only meant for estimation purposes. Battery life is dependent on many factors as detailed below, so use this tool only for estimation.
The triggers can be used to significantly increase battery life. The article on battery specifications includes a calculator that estimates battery life. Here are some examples that highlight battery life with different trigger settings (and these are estimates and assume a brand new 250 mAh battery):
- 12 hours: Standard sample rates, full recording (5 kHz main accelerometer, 400 Hz DC, 100 Hz orientation, 10 Hz pressure and temperature)
- 16 hours: high-power acceleration trigger mode that guarantees pre-trigger samples in sleep mode 90% of the time
- 46 hours: low-power acceleration trigger mode that uses the low-power accelerometer (no pre-trigger samples) when in sleep mode 90% of the time
- 64 hours: low-power acceleration trigger mode that uses the low-power accelerometer (no pre-trigger samples) when in sleep mode 99% of the time
- 116 hours: when using a time based/periodic trigger with sleeping 90% of the time
- 1136 hours (47 days): when using a time based/periodic trigger with sleeping 99% of the time
For more on setting triggers, visit the trigger article.
External Power Source
When powering the device over USB while in operation, be certain to strain relief the USB cable to prevent putting too much force on the USB receptacle. This can cause damage to the electrical connection between the USB receptacle and the PC board.
Recommended Portable USB Source
The device can be powered with a standard USB power source. But some portable USB chargers have "features" that detect the current draw and shut off charging to preserve battery capacity. This will result in charging the device to a full charge, then turning off, and not starting charging again as the sensor slowly looks to consume current.
We recommend Voltaic's batteries that have an "Always On" feature to directly address this issue. These batteries will always provide power and so they can be used to significantly extend battery life.
Configuration for External Power Source
In order to be powered over USB, the device must be configured with the "Plug-in Action" as "Ignore: Stop recording when the button is pressed." For more, visit the article on configuration settings.
Battery Life Factors
There are many variables that influence the expected life of a lithium-ion polymer battery. All rechargeable batteries are consumables and have a limited lifespan - eventually their capacity and performance decline significantly. The major factors that contribute to this aging process are:
- Age measured in charge cycles
- Age measured in time
- Temperature exposure
About lithium-ion batteries
The recorders use lithium-ion battery technology. Compared with older generations of battery technology, lithium-ion batteries charge faster, last longer, and have a higher power density for more battery life in a lighter package. Rechargeable lithium-ion technology currently provides the best technology for most applications.
How to maximize battery performance
“Battery life” is the amount of time a device runs before it needs to be recharged. “Battery lifespan” is the amount of time a battery lasts until it needs to be replaced. One factor affecting battery life and lifespan is the mix of things you do with your device. No matter how you use it, there are ways to help. A battery’s lifespan is related to its “chemical age,” which is more than just the passage of time. It includes different factors, such as the number of charge cycles and how it was cared for. Extended periods of time at low or high temperatures will significantly decrease the battery capacity over time. Another way to improve battery capacity over time is to store the battery at about a 50% charge for long periods of time, and periodically charge it (again to 50%) once every 4 to 6 months.
We recommend charging the sensor once it is received. Connect the Micro-USB cable provided with each device to a power source and the sensor itself as shown in Figure 5. The power source can be a computer, AC wall adapter, or portable phone charger as long as the power source does not exceed 5 volts of supplied power.
We recognize the need for longer battery life and have begun developing a new recorder that will utilize the Saft MP 174565 xtd battery. This battery has a 4,000 mAh capacity and a much more stable low-temperature performance than the existing batteries. The datasheet of this battery is available here.
When the battery is about to die and the device shuts down, will it save the data?
Yes. The recorder has a lot of protections and checks in place to sense the battery voltage dropping and will then close out the file beforehand. That being said, there are occasions where the battery voltage will drop too quickly and the file may not get closed out. This can result in a corrupt file that often can be fixed by Mide if need be. To help mitigate this, we recommend using recording limits and re-trigger mode to be continually closing files and creating new ones through a particularly long test.
Can the battery be replaced?
No. The bottom volume of the recorder is potted with an epoxy to mechanically stiffen the assembly and directly couple the accelerometers with the bottom of the enclosure. This potting extends into the volume where the battery is located, so it can not be replaced. All units can operate while plugged into power so the device will not be completely useless. But do keep in mind that depending on use, charge cycles, temperature etc. the battery lifetime is 2 to 3 years.