Vibration anomaly detection device with solar LTO batteries

In the previous Hackster post, we dealt with the development of a vibration-anomaly detection circuit board. The IIS3DWB vibrometer from ST Microelectronics is an impressive piece of hardware, but it is quite power-hungry if we log the data at full speed. Moreover, if we want to add other monitoring elements such as a camera, we will need to obtain more energy from our batteries. In addition, I wanted to test Lithium Titanate Oxide (LTO) batteries that claim > 20, 000 charging cycles, which makes them ideal for long-term monitoring. So, let us look.

🔋 LTO batteries

The LTO is a rechargeable battery based on or modified from the lithium-ion (Li-ion) battery technology. Li-titanate oxide (LTO) replaces graphite in the anode of a typical Li-ion battery and forms the materials into a spinel 3D crystal structure. With a nominal cell voltage of 2.40V, it releases a high current discharge current that is 10 times the capacity of other types of lithium batteries. Instead of using carbon particles on its surface as in other lithium batteries, Lithium Titanate utilizes lithium-titanate nanocrystals.

The effect and benefit of this alteration and the inclusion of lithium-titanate nanocrystals is that the surface area of the anode is approximately 100 square meters per gram, in contrast to only 3 square meters per gram of Li-ion batteries. The result of the lithium-titanate nanocrystals with their enlarged surface area is that electrons are able to enter and leave the anode much more rapidly, leading to fast recharging and an enhanced battery lifetime.

Given the basic scientific advantages of high-tech nanotechnology involved in producing Lithium Titanate (LTO) batteries, the benefits for the IoT range from long lifetime to enhanced safety and low-temperature performance.

-Extremely Long Lifetime 🛰️

As discussed above, advanced nanotechnology consisting of lithium-titanate nanocrystals and their increased surface area is especially designed to enhance the lifetime of these batteries. As a result, the cycle count of a Lithium Titanate battery is 20,000 in comparison with only 2,000 in a regular lithium battery, marking a revolutionary approach to energy storage for very long-term IoT monitoring.

-Low-Temperature Performance ❄️

Another advantage of using Lithium Titanate batteries is that, owing to the nanotechnology employed, these batteries have a much better low-temperature performance than other battery technologies.

Owing to these low-temperature discharge characteristics, it is possible to obtain up to 80% of its full capacity at a mere -30°C. This is of particular benefit to companies that employ Lithium Titanate technologies at lower temperatures in regions with cold winters.

☀️ Solar charging circuit

The solar LTO battery charging circuit uses SPV1040 step-up from ST Microelectronics for the solar panel´s power MPPT, BQ34Z100 from Texas Instruments as a battery fuel gauge, and a TPS63060 Buck/Boost converter from ST for battery power output. A portion of the schematic is shown below:

The device can therefore work in outdoor conditions all year round. It´s features include:

• LTO batteries (4x LTO1865) cells
• 1.3 Ah (per cell)
• MPPT tracker for LTO batteries charging from solar cell
• Battery gauge for battery charge state measurement
• I2C interface
• LED indication
• Output switching voltage regulator
• Standard output voltage 3v3