The 134N3P is an excellent solution to add battery power to portable devices (like microcontroller projects): it supports LiIon/LiPo batteries and can both charge them as well as boost the battery voltage to a stable 5V USB output.
134N3P refers to both a power management chip and the breakout board that is using it. There is no dedicated *134N3P datasheet available, nor can you order this chip separately. The chip on the board has no markings.
Overview
Technically, 134N3P boards combine battery charging logic (similar to a TP4056), and a boost converter that steps up the battery voltage (3.0-4.7V) to USB 5V Output.
Dedicated chargers (like TP4056) typically have no coil on the board (which is part of the boost converter that pure chargers lack).
Supported Batteries
You can connect any single LiIon or LiPo battery to the board. Other chemistries, especially LiFePo4, are not supported and must not be used.
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Check Charging Current: Since the board charges with a maximum of 1A, the connected battery needs to support this charge current. 1A may be too much for very small batteries (<1000mAh). Check the battery specs.
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Add More Batteries in Parallel: To increase battery capacity, you can connect multiple cells in parallel (never in series!). This can also help with batteries that require less than 1A charging current.
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No BMS Required: Since the board comes with BMS functionality like over-charge protection and over-discharge protection, a separate BMS is not required. Once you connect multiple batteries in parallel, though, you should add your own balanced BMS.
USB 5V Output
The board provides an output of 5V with a peak current of 1A (500mA continuously is a safe assumption). That is perfect for supplying power to microcontroller projects.
Output power is available on both USB connectors, and there is overload protection and short-circuit protection built-in.
Charging Current
The board charges a LiIon/LiPo cell with a maximum current of 1A.
It accepts USB power at its USB-C/Micro-USB connector. The USB-A connector is output-only and cannot be used for charging.
Portable Power Supply for DIY Projects
The maximum charging current of 1A is perfect for many portable DIY solutions:
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Low-Capacity Batteries: Since portable DIY projects aim to be small in size, and typically do not require excessive power, small LiIon or LiPo batteries are used, with limited capacity (1.500 mAh or less).
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Preventing Over-Charging: Even at 1C charging rate, a charging current of 1A is often already close to the upper range of what these batteries can accept.
Most comparable boards use much higher charging currents. They are unsuitable and sometimes even dangerous to use with small batteries (for example, boards based on IP5306 with >2A charging current).
Power Bank
If you intend to use this board to build a generic power bank to charge your USB devices, this is perfectly fine: you can charge up to two devices (one on USB-A, and the other one on USB-C/Micro-USB).
Just be aware that the 1A output current allows for charging your devices at a maximum of 5W. There are no sophisticated “quick charge” modes either (most dedicated smartphone chargers charge with 10-20W).
Specifications
| Specification | Value |
|---|---|
| Input Voltage | 3.7 V – 5.5 V |
| Output Voltage | 5 V |
| Charging Current (max) | 1 A |
| Output Current (max) | 1 A |
| Charging Voltage (preset) | 4.2 V (±1%) |
| BAT Discharging Stop Voltage | 2.9 V |
| Discharging Efficiency | 85% (input 3.7 V, output 5 V/1 A) |
| BMS | - Output overvoltage protection - Short-circuit protection - Overload protection - Over-charging protection - Over-discharging protection |
| Reverse Polarity Protection | no |
| Trickle-Mode | supported |
| Zero-Voltage Charging | supported |
| LED | red: on=load connected, blinking=charging, off=standby |
| Standby Current | 8 μA (max) |
| Operating Temperature Range | -30°C to +85°C |
| Module Size | 23 mm × 17.5 mm × 12 mm |
| Weight | ~3 g |
The board has no reverse polarity protection: always make sure you connect the battery in correct polarity, especially when using a battery holder.
Board Differences
When you google for 134N3P, you quickly find a vast number of offers. Buying the board in quantities drops the price to €0.30 or even lower.
Boards differ primarily in the USB connectors: blue boards use an old Micro-USB connector whereas green boards use a modern USB-C connector. Both boards come with an additional USB-A connector.
- USB-A: output only.
- USB-C/Micro-USB: input and output, can be used for charging
Use Cases
By adding a single LiIon/LiPo battery to this board, you essentially create a simple power bank.
Power Bank
Turn any single LiIon/LiPo cell into a (very) simple power bank that can be used to charge USB devices.
Since the board outputs a maximum of 5V 1A, such a power bank can charge USB devices at a maximum of 5W (which is much less than “real” power banks or USB chargers can do). Charging USB devices will therefore be relatively slow.
If you need more battery capacity, connect multiple batteries in parallel (not in series). This will improve the energy your power bank can store, but it will not affect the speed in which it can charge USB devices.
Powering Microcontrollers
A much more rewarding use case for the 134N3P is acting as power supply for portable microcontroller projects.
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For this, you could de-solder the clumsy output-only USB-A connector and just keep the USB-C/Micro-USB connector for charging.
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Wire the 5V output from the de-soldered USB-A connector directly to the 5V input of your microcontroller board.
Wiring
Wiring is simple: just solder a battery holder to the B+ and B- solder pads.
- Power Switch: You may want to add a switch to the battery holder wiring so you can turn off the battery. Else, the 134n3p board draws a constant 8uA quiescent current.
- Missing Reverse Polarity Protection:
- If the battery in your device is non-servicable, you just need to be careful once when you assemble your device.
- If your device allows users to change/replace the battery, add a ideal diode board to protect the user from reverse polarity which can destroy the board in a split second.
- BMS: 134N3P comes with over-discharge, over-charge and short circuit protection. No additional BMS board required.
Operation
Once you connect the board to a battery, it immediately switches to standby mode. In this mode, power consumption is minimal (8 μA). The built-in red LED is off.
With a USB tester you can already detect 5V. However, the output is instable, and your USB tester will reboot in intervals of a few seconds.
In Standby mode, 134N3P just monitors the outputs. The boost converter is not fully running.
Connecting Load
Once you connect a load to either one of the boards USB connectors, the 134N3P detects it and switches to full operation: a red LED lights up, and it provides a stable power source now.
Output power is available on both USB connectors.
Note the current direction in the USB tester display: energy is flowing from the USB-C connector to the load.
Charging
To charge the battery, connect a USB power source to the USB-C/Micro-USB connector.
Note the current direction in the USB tester display: now energy is flowing from external USB to the board.
The red LED is blinking during charging.
When you connect a USB power source to the board, it may take a few seconds until the charging process starts. The built-in red LED is a valuable indicator: it starts blinking after a few seconds, indicating that charging has begun.
Trickle-Charging
This board supports trickle-charging and zero-voltage charging, which means you can use it to try and recover dead cells.
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Deep-Discharged Batteries: Many chargers start charging only when the battery cell has a minimum voltage of around 2.5V. If a battery cell has accidentally been deep-discharged (i.e. due to natural self-discharging over some time), its voltage may no longer be above 2.5V, or even 0V.
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Normal Charging Impossible: Charging such a cell with normal currents is dangerous because at such low voltages, batteries cannot accept high currents. That’s why some chargers refuse to charge at all at these voltages.
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Trickle-Charge at 0V Battery Voltage: 134N3P automatically switches to trickle charging under such conditions: a very low charging current is applied in intervals until the battery voltage has recovered.
So if you have dead LiIon/LiPo cells that your normal charger wouldn’t charge, you may try to charge them with 134N3P boards. Chances are that they may recover.
Discharging While Charging
You can discharge (power a device) while charging:
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No Interruption When Adding Charger: Connect a device to the USB-A connector. It will be supplied by the battery, and when you insert a USB-C charging cable, there is no interruption, and you can continue to use the device while charging.
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Interruption When Removing Charger: However, when you remove the USB-C charging cable, there will be a short interruption, and your connected USB-A device will lose power for a short moment.
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(content created Jun 06, 2025)