2s Li-ion battery (bicycle light) charger for cars

I made this for charging my bicycle light battery pack in the car.

1. A TP5100 charging module (ebay) has been used

2. Cut the cord and solder the wire on the charger module.

3. Packaging in a plastic enclosure

Because the charging indicator LED would not be seen with the case closed, I drilled a hole on the case lid and plugged a clear acrylic screw.

3. The test was successful and it charged my battery pack like a charm.

Multi-purpose variable voltage DC power supply for cars

Intended use: charging laptops and smartphones in cars, for example, at a campsite without an electricity hook-up.

Features:

USB PD 18W

QC 3.0

Low input voltage (car battery) alarm

Variable DC output

Left slot: USB PD and QC 3.0 charging ports
Middle slot: Voltage meter for the DC port on the right slot
Right slot: DC output port

For the DC output, I used a SEPIC converter module, which purchased on ebay. This converter module provides 5A output currents with 1V-30V voltage range.

To avoid over-draining the car battery, a low battery alarm module from aliexpress has also been added.

On the back, there are vent holes for cooling, power switch, and voltage adjusting knob.

LED turn signal relay MOD

1. Remove turn-signal relay from the car (TOYOTA 81980-02030)

2. The stock relay comes with a 0.03 Ohm current-sensing resistor, which detects over or under-load conditions. The most typical case for the under-load condition is that a turn signal bulb is out. Upon detection of this condition, the blinking frequency is doubled (a.k.a., hyper flash). On the other hand, when the over-load condition is detected, the blinking stops after a single blinking.

In my case, the replacement LED bulbs consumes approximately one third the power of the original Halogen bulbs. Thus, I decided to replace the current sensing resistor with a 0.1 Ohm resistor.

 3. Resistor replacement is done!