Introduction: BETAFPV 1S BT2.0 Battery Charger 4.2V Mod

This simple reversible mod change charge voltage from 4.35V down to 4.2V, thus reducing battery wear

Supplies

  1. BT2.0 Battery Charger and Voltage Tester V2 (Link)
  2. Soldering iron
  3. Solder
  4. [Optional] Thin wire

Step 1: Split the Case

Split the case by hand or use a knife to pry open

Step 2: Take Out PCB

PCB is just tightly fitted in the plastic case an can be removed by hand

Step 3: Find Voltage Set Resistors

According to documentation voltage set resistor is connected to FB pin. To be sure you can measure resistor value with multimeter without desoldering it. It should be around 40kΩ - 50kΩ

Step 4: Bridge Resistor to Make 0Ω Connection

Max charge voltage can be changed by changing resistor value.

Manufacturer set it to 4.2V + 0.15V = 4.35V which according to the formula requires Rx = 0.15V / 3.01 / 10^(-6) = ~50kΩ resistor.

But to set it to lowest possible voltage 4.2V resistor should be 0Ω aka no resistor.

This can be achieved 2 ways:

  1. Solder thin wire to both sides of the resistor to short it (recommended because it can be easily undone)
  2. Desolder resistor and bridge the pads with solder

Step 5: Test

Now it should charge to roughly 4.2V