Solar + Li-Ion Power Supply Unit
This week we started testing our brand new solar charger PSU design. The solar PSU powers a WiSense WSN1120L node operating in full function device (FFD) mode. FFDs are involved in mesh routing and therefore need to keep their radio on at all times. The WSN1120L’s current consumption in this mode is around 31 mA in normal receive mode and around 50 mA when transmitting at +13 dBm.
The solar PSU also supports continuous measurement of the panel voltage and current as well as the battery voltage and current. This data is being sent every 5 minutes to the cloud. See the graphs at the end.
The PSU supports panels with voltage output up to 10.5V. The PSU allows charge current of up to 2 A which allows high capacity Li-Ion batteries to be charged by high wattage panels.
Test Panel Specs
- Peak power: 3 Watts
- Voltage output at peak power point: 8.5V
- Current output at peak power point: 300 mA
Test Battery Specs
- Chemistry: Single cell Lithium-Ion Battery
- Capacity: 1100 mAh
- Output voltage: 3.7 V (nominal), 4.2 V (full charge)
Charger PSU Board Specs
- Max input voltage: 10.5 V
- Max charge current: 2 A
- Max battery discharge current: 4 A
- Li-Ion battery charged in 3 phases (trickle charge, pre-charge, constant current and constant voltage).
- Battery under-voltage lockout supported as load is not connected directly to battery.
- Charger IC can power the load and charge the battery simultaneously.
- Multiple output voltages
- 3.3V (Max 1 A)
- 4.9V (Max 50 mA)
- Li-Ion battery output (Max 4A). This supply is gated by a load switch which can be controlled by a signal external to the PSU (for example – by an external micro-controller).
- On board current and voltage sensors which measure the following parameters:
- Solar panel output voltage (Available over I2C)
- Solar panel output current (Available over I2C)
- Battery voltage (Available over I2C)
- Battery current (Available over I2C)
- PCB specs
- Layers: 4
- Dimensions: 53 mm x 48 mm
- Mounting holes: 4
- Finish: ENIG
Here is a pic of the setup. You can see the 3W panel lying flat and connected to a weather proof enclosure containing the PSU, battery and an WSN1120L. This location is not the best with tall structures/buildings in the vicinity.
Snapshot of battery voltage and current (captured from WiSight running on AWS).
For more information on our products, please visit wisense.in.