The USB LiPo Charger provides a convenient way to charge 3.7V Li-Poly cells (or parallel matched sets of cells at 3.7V) from a 5V USB source such as a computer or a mobile phone charger.

Setting The Current Limit

The USB LiPo Charger uses an onboard charge management chip that monitors the state of the battery and adjusts the charge current accordingly. If the battery needs significant charging it will supply current up to the maximum rate set by the current limit jumpers on the bottom of the PCB. Both jumpers are open by default, setting the current limit to 100mA.

Check the specifications for your battery to determine the maximum charge current. If you battery can sustain higher charge rates you can place solder bridges across one or both current limit jumpers to change the settings as follows.

SJ1 SJ2 Charge Rate
Open Open 100mA
Open Closed 200mA
Closed Open 300mA
Closed Closed 500mA


Fitting The Battery Connection

Because different batteries use different connections, the USB LiPo Charger does not come with a battery connector but does include two pairs of pads for you to fit the specific connector to suit your battery.

The smaller, inner pads suit typical 2mm JST connectors used on many batteries, while the outer, 0.1" pads suit larger connectors, headers, flying leads, or even small screw terminals.

Pay very careful attention to the polarity of the connections. The PCB has "+" and "-" marked on both the top and bottom of the PCB. Fit the connector for your battery on either the top or the bottom of the PCB, depending on how it should be polarised.

Note: When soldering the connector be very careful not to leave a solder bridge between the output pads. Doing so will short circuit both the output of the charger and any batteries you connect to it.


1. Connect your battery to the output of the charger.

2. Connect a micro USB cable to the input of the charger and connect to a computer USB port, or connect a mobile phone charger with a micro USB connector.

3. While charging, the orange "Charge" LED will illuminate and the charger will supply up to the maximum current configured by the current limit jumpers. As the battery approaches full charge the charger will automatically decrease the current until full charge is reached.

4. When charging is complete, the green "Standby" LED will illuminate and the charger will stop supplying current to the battery.