Solar Power Manager Series

Introduction

The DFRobot Solar Power Manager series are designed for IoT and renewable energy projects, providing safe and high-efficiency embedded solar power management modules for makers and application engineers. All modules in this series have MPPT (Maximum Power Point Tracking) to maximize solar energy conversion efficiency under various sunlight. A complete battery and power protection provides reliable power management for different types of solar projects.

Selection Guide

Name Solar Power Manager Solar Power Manager 5V
SKU DFR0535 DFR0559
Solar Power Management IC LTC3652 CN3065
Solar Input Voltage 7V ~ 30V 4.4V ~ 6V
Maximum Charge Current 2A 900mA
Topology DC-DC Buck Linear Regulator
Battery 3.7V Lithium Battery 3.7V Lithium Battery
MPPT Yes (9V/12V/18V Optional) Yes(Fixed 5V)
Battery Protections Over Charge/Over Discharge/Over Current/Reverse Connection Protections Over Charge/Reverse Connection Protections
Output Protections Short Circuit/Over Current/Over Heat Protections Short Circuit/Over Current Protections
USB Charge IN Yes Yes
USB OUT 5V 1.5A 5V 1A
Regulated OUT Three Regulated Outputs (3.3V 1A;5V 1.5V;9V/12V 0.5A) One Regulated Output (5V 1A)
Dimension 78.0mm×68.0mm 33.0mm×63.0mm
Features A complete multifunction solar power management module.
Applications: Small Solar Street Lamp, Solar Powered Robots
For 9V/12V/18V Solar Panels within 20W
A small and easy-to-use 5V solar power management module.
Applications: Solar Power Bank, Solar Environment Monitors
For 5V Solar Panels within 10W

Introduction

DFRobot Sunflower is a new series focusing on high-efficiency small power solar energy harvesting and management for makers, low-power applications and IoT projects. Solar Power Manager 5V is a small power and high-efficiency solar power management module designed for 5V solar panel. It features as MPPT (Maximum Power Point Tracking) function, maximizing the efficiency of the solar panel. Apart from serving as a solar charger, the module can provide up to 900mA charging current to 3.7V Li battery with USB charger. The ON/OFF controllable DC-DC converters with 5V 1A output satisfies the needs of various solar power projects and low-power applications. The module also employs various protection functions, such as battery/solar panel reverse connection protection, output over temperature and over current/short circuit protection, which greatly improves the stability and safety of the system.

Features

Specifications

Applications

Board Overview

DFR0559_overview(EN).png

Quick Start

Build a solar powered system

warning_yellow.png NOTE: This module DOES NOT has over-discharge protection. We highly recommend users to use a lipo with protection circuits to prevent over-discharge problem. Over discharging LiPo batteries will lead to permanent damage and the build up of gasses inside. If the battery is then charged, the compounds in the battery become reactive and combustible. This may finally cause the battery to explode or on fire.

Attention

Solar powered system

Detailed Description

Maximum Power Point Tracking, MPPT

The MPPT (Maximum Power Point Tracking) can ensure the solar panel output power maintains at its maximum under different loads and sunlight, maximizing the conversion efficiency. We can identify the short circuit current ISC and the open circuit voltage VOC from the cross points of the I/V curve (green) with x and y axis respectively. The ISC and VOC grow larger with the illumination increasing. With the output voltage VPANEL growing, the output current IPANEL gradually decreases and then jumps down after crosses a special point VMP, the maximum power voltage. By multiplying the voltage and current, which obviously results in power, and take the output voltage as the x axis, we obtain the P/V curve (blue). The output power PPANEL reaches its peak when the output voltage is at VMP. Although the maximum power increases with illumination, the VMP changes little. Therefore, we may approximately take the VMP as a constant for a specific solar panel under different illumination. IV/PV characteristic curve of a typical solar panel (picture from Linear Technology)

Inspired by the observation above, the CN3065 solar power management IC (employed by this module) maximizes the output power by keeping the output voltage at the vicinity of VMP, which is also called constant voltage MPPT algorithm. Benefited from this feature, the module has a better conversion efficiency compared to common linear battery charger.

Solar Panel Selection

The module is designed for 5V (nominal/maximum power voltage) solar panel. Any kinds of panel (monocrystal, polycrystal, thin flim) can be employed as long as the open circuit voltage is less than 6.5V. Taking the size, weight, price of the panel and the 900mA maximum charge current of the module all these factors into consideration, it is recommended to connect a solar panel with no more than 10W to the SOLAR IN terminal.

warning_yellow.png NOTE: The input voltage of SOLAR IN SHOULD NOT exceed 6.5V, or the module may be permanently damaged.

Battery Selection

The battery input BAT IN provides two connectors JST PH2.0 and KF396 3.96mm 2P terminal, which directly connect each other internally. Usually, connect one 3.7V Li-polymer/Li-ion battery (4.2V when fully charged) to one of the connectors. The maximum charge current can be up to 900mA for both USB IN or SOLAR IN. Safety issue may arise if the charging current exceeds the nominal charge current of the battery, which is often determined by the capacity and charge rate of a battery. The maximum allowable charge current of a battery can be calculated with the equation: Maximum charge current(mA) = Capacity(mAH) * Charge rate(C). Use this equation to check whether the battery is suitable. For commonly used 1C (charge rate) Li battery, the capacity should be at less 900mAh. For higher charge rate battery, smaller capacity can be used. Some Li batteries are packed with battery protection circuit to automatically limit the charge/discharge current. For such batteries, users are free of worrying about the charge current issue stated above.

warning_yellow.png NOTE: DO NOT use nonchargeable battery or chargeable battery not described above.

USB Charge Requirement

The USB IN is only used for battery charging. It is recommended to use at less a 5V 1A AC adapter for battery charging.
USB IN charge input

USB/SOLAR IN Automatic Switching

Both the USB IN and SOLAR IN are capable of deliver 900mA max charge current. To prevent charge conflict caused by using both inputs, the USB charge has a higher priority. When the USB IN is powered on by AC adapter, the SOLAR IN will be automatically cut off. When the USB IN is powered down, the SOLAR IN resumes charging.

Regulated Power Supply

The module provides a ON/OFF controllable 5V 1A regulated output. The 5V outputs of the header and USB OUT share the same output voltage and maximum current, however, USB OUT CAN NOT be shutdown.

Most of the power banks available on the market has the automatic shutdown function to reduce the quiescent power under light loads. However, the automatic shutdown threshold is usually higher than many low power controllers, some even higher than the classical Arduino UNO (around 50mA). Such power banks will automatically shut itself down when the output current continues lower than some preset threshold after several seconds, which fails to apply to low power applications. The USB OUT employs the low quiescent power DC-DC boost converter and always remains ON to provide continuous power to low power controller.

5V USB OUT

Except from USB OUT, the header 5V output can be turned ON/OFF by all 3.3V and 5V controllers (such as Arduino, FireBeetle or Raspberry Pi etc.). Pull out the jumper on the blue header, the output will be shutdown (LED indicator ON turns dark). Connect any IO and GND pin of the controller to the EN and GND pin of the blue header. When the IO pin is driven HIGH, the regulated output turns on. When driven LOW, the output turns OFF. This function is extremely useful in low power application. For example, connect all VCC and GND pins of the peripherals (sensors or other modules) to the 5V and GND pins. Turn on the regulated output and read all the data from the sensors. Turn off the output and put the controller into sleep mode for 1s (for example) until next wake up. By cycling the system into such discontinuous (or pulse) operation pattern, the average power consumption can be greatly reduced. Average power consumption and data acquisition interval are the trade off under such situation.

Attention

5V header output

LED Indicators

There are three types of LED indicators indicating the operation status of different parts of the module:

DFR0559_REV_BAT.png

DFR0559_REV_SOLAR.png

DFR0559_CHG_LED.png

DFR0559_ON_LED.png

Cooling Fin installation

If an USB AC adapter or a 10W (or above) solar panel is used, the solar power management IC CN3065 may run into full-load. The chip has over-temperature protection function, which will automatically limit the charge current, trying to protect the chip. To improve cooling and maximize charge current, which results in longer life-span and better performance, it is highly recommended to stick the Aluminum cooling fin with the blue thermal conductive silica pad to the bottom of the module, where the label “Cooling Fin” is located. Cooling fin install location

Protection Functions

Application Examples

Use the USB to charge battery Ultilize the USB charge function, the user can build a USB/solar power bank for outdoor sport application. Charge the battery with solar panel by daytime and USB at night with cell phone charger (if it is available). User can also charge small charge current, low power devices, such as smart band or Bluetooth headset with the USB OUT. Use USB charger to charge Li battery Build a low power environment monitor station This application example use the BME280 environmental sensor to record temperature, humidity and atmospheric pressure, VEML7700 ambient light sensor to record the the ambient illumination, and DS1307 RTC module to record time. Use the analog input A1 to monitor the battery voltage (equivalently the battery capacity). To achieve lower power consumption, use one Arduino digital IO pin to turn ON the power supply, read all the data from the sensors and turn them OFF. Cycle this pattern for a proper interval T to reduce the average power consumption. This can completely get rid of the quiescent power of the peripheral modules. Although single peripheral may consume little power, it can be considerable large for a number of them. This module provides users with effective methods to drive the peripheral modules into discontinuous (pulse) mode to achieve low power operation. Low power environment monitor station

FAQ

Some general Arduino Problems/FAQ/Tips
Q Can I connect two battery to each of the BAT IN connectors?
A Yes. But pay attention that these two batteries are in direct parallel connection. It is required that these two batteries are of the same (or near) specifications. The two connectors are designed to be compatible with more battery interfaces. Usually, pick one to connect a single Li battery.
Q Can I charge the battery while using the regulated output?
A Yes
Q Is there any overdischarge protection on BAT IN ? What is the overdischarge cutoff voltage?
A No, but the equivalent overdischarge cutoff voltage is 2V. We recommend users to use a lithium battery with a battery protection circuit. Although there is no battery overdischarge circuit on the module, but the internal DC-DC boost circuit input cut-off voltage is 2V, that is, when the battery voltage is lower than 2V, the boost circuit stops working. This equivalently avoids further discharging the battery. Usually, the 3.7V lithium battery overdischarge cutoff voltage is 2.7V or 3V (some of the IC manufacturers' lithium battery protection IC can be as low as 2.4V). However, 2V equivalent overdischarge cutoff voltage is too low for the general 3.7V lithium battery. The battery has already been in an overdischarged state when discharged itself to 2V, which causes some damage to the battery. Therefore, users are advised to use a 3.7V lithium battery with a battery protection circuit.
A For any questions, advice or cool ideas to share, please visit the DFRobot Forum.

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