Solar charged Li-Ion capacitors developed jointly by E-peas and Voltaic

Date: 17/10/2022
Lithium Ion Capacitors (LICs) are great alternative to traditional lithium ion batteries in many LPWAN applications. While less power dense, they have a very broad temperature range and a very high amount of rated cycles (50,000+). Combined with the right panel, they can easily last 10+ years and dramatically reduce the costs of battery replacements.[

We have designed two solar chargers based on Lithium Ion Capacitors. The latest is in collaboration with e-peas, a leader in PMICs for energy harvesting.

E-peas, the leader in PMICs for energy harvesting, and Voltaic Systems, the leader in solar systems for IoT, combine their unique value propositions of high-performance power management Ics (PMICs) and photovoltaic cells to offer hardware an ultra-compact, lightweight, long-lifetime energy supply solution for heavy-duty applications. This Lithium-Ion Capacitor (LiC) based solar charging solution eliminates battery replacements and ensures performance across a broad range of operating temperatures.

The solution is intended to power outdoor IoT sensing applications including those like the Generic Node running on The Things Industries LoRaWAN network. Customers are expected to use the solar charger for applications across agriculture agriculture data collection, environmental monitoring and asset tracking.

The collaboration focuses on the e-peas AEM10941 highly efficient MPPT-based DC/DC converters, together with Voltaic System P121 high-current high-energy photovoltaic cell. The combination of high energy production PV (up to 300mW @1SUN) + High current PMIC (110mA) + High-capacity Storage element (250F) makes it extremely well suited for majority of heavy-duty systems like LPWAN connected nodes using LoRa and of the latest generation LTE CAT-M, NB-IoT.

Voltaic System 0.3-Watt, 2 Volt P121 solar panel combines a small form factor (5×5 cm2), high current, and a UV-resistant and waterproof construction. This design has been thoroughly qualified for long-term outdoor exposure, temperature cycling and vibration.

The e-peas AEM10941 is configured with it’s popular “custom mode” to extend the Overcharge / Charge ready / Over-discharge to the following values: 3,6V/2,7V/2,5V, ensuring maximum longevity of the storage element without compromising on readiness of supply for the application.

The Vinatech LiC hybrid capacitor provides 250F, charged up to 3.6V, of energy storage. The available energy from this LiC is approximately 900 Joules. The is rated for 50,000 cycles and operates between -20°C and 70°C. The module is designed to protect the LiC against over-discharge and over-and under-temperature situations.

The Voltaic photovoltaic cell and e-peas PMIC charge the Lithium-Ion Capacitor quickly. Even if completely discharged, it can be fully charged in about 2 hours at 1SUN.

The large storage of the PV + PMIC means the module can also survive for periods of extended darkness. Assuming the end device consumed the average current consumption of a popular LPWAN chipset (as low as 28µA.), the module would run for three months without any sun.

The energy harvesting system (PCB + LiC + connectors) is packed into a compact design of ~2cmx6cm including all featured capabilities. The LiC storage element is tightly fixed to the PCB with a mini strap. Power input from the solar panel and power output from the PMIC are via standard JST connectors.

Samples can be provided upon request:

News Source: e-peas

Author: Srinivasa Reddy N
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