Raspberry Pi Lithium Battery Power Pack
The power module is designed for the Raspberry Pi 3 Model B specially, allowing the master board to work offline for up to 9 hours. It's not only supplying for Raspberry Pi; this board has 2 USB type-A ports – one supplies power for the Raspberry Pi and the other for the embedded LCD screen.
The module integrates a Li-ion battery charger IC, a boost management chip. And it is developed in strict accordance with the size of the international Raspberry Pi expansion board HAT, using only simple copper standoffs to install multi-layer Raspberry Pi boards.
A charging/boost integrated chip lies under the heat sink on the extension board, which is the center of the whole board.
Let’s learn about the principle of the extension board:
1. When connected to power, the working charging/boost chip can work under either the charging mode or step-up mode at one time.
2. If the USB type-A power output ports do not have any external load connected (like RPi), just input 5V to the Micro USB charging port, then the charging/boost chip enters the charging mode. Since the chip has already integrated a current-limiting resistor by default, the voltage will charge the Li-ion battery and output around 4.6-4.7V via the USB type-A port. (The ON LED will light up, no matter whether the power output switch is on or off.)
3. The chip will enter the step-up mode without the 5V voltage input (namely, not charging). In this mode, turn on the switch for boosting, each USB type-A port can output a maximum 5V voltage, and two ports can output a maximum 1.8A current in total. The chip comes with the current-limiting protection, for example - e.g., it will be shorted and shut when the output current is 1.9A or larger.
Battery capacity: 3800mAH
Maximum discharge current: 1.8A
No-load output voltage: 5.1V ± 0.1V
Standard charging current/voltage: 1.0A/5.0V
Cut-off voltage of fully charging the Li-ion battery: 4.18V - 4.2V
Q1: How long can this power pack work for RPI 3?
A: The duration depends on the loads. If you just connect a RPI 3 with timing program running in the background, it can last 9 hours. If you connect a small 2.2 inch, or 3.5 inch LCD screen, it can last 6 hours on average. Well, a smaller size LCD will last longer. The time is 2.5 hours for an HDMI 5 inch or 7 inch display.
Q2: How long does the power pack need to be fully charged?
A: It depends on the input current into the 5V Micro USB input port. Usually we suggest charging with 5V 1A. It can also be 5V 0.5A or 5V 2.5A, because the chip will adjust the charging current itself. The max current required is 1A, but the actual current in constant charging will be 0.7A-0.8A, while the current in floating charging is 0.1-0.3A. When fully discharged, if charged with 5V 1A, it needs around 3 hours.
Q3: How to tell when the battery is fully charged?
A: You can check the CHG LED (Charge LED). When the red LED lights up, it means the battery is in charging. When the red LED dims, it means the battery has been charged to 95% capacity. It can be full after one more hour of float charging, normally.
Q4: Can the board power the RPi 3 when charging the battery at the meantime?
A: In principle, no. But the charging/boost chip can output 4.6-4.7V voltage via the USB Type-A port to power an RPI 3. Under this circumstance, please note that the chip is in charging mode, so it’s the voltage after flowing current-limiting resistor that powers the RPI 3. It can't be used to power RPi 3 and other large-power devices at the same time, for it will result in unstable use. It'd better be applied only when it just powers one RPi 3 which remotely connects with other devices via SSH.
Q5: What if the CHG red LED blinks, and the charging/boost chip fails to enter charging mode?
A: When you connect the RPI 3 to the USB type-A port and power the Micro-USB with 5V at the same time, the chip will not enter either mode, and the Charge LED will flash. The solution is to remove the RPI 3 and turn off the power output switch. Then input 5V voltage to the Micro USB port, so the chip will enter the charging mode, and the red LED will light up constantly (indicating the battery is in charging).
Q6: Can users replace the Li-ion battery?
A: Of course they can. One thing to mention, the replaced battery must be 3.7V for one cell, and you can choose the capacity you want, like 5000-10000mAH. The larger capacity you use, the larger dimension (L, W, H) the battery will have. And make sure the battery polarity (anode and cathode) of the new battery should match that of the old one, or the chip will get burnt!