IOT123 - Solar 18650 Charge Controller

Originally devised for the SOLAR TRACKER (Rig and Controller), it is fairly generic and will be used for the upcoming CYCLING HELMET SOLAR PANELS.

The controller screws directly onto the battery holder, minimizing the footprint and lead lengths.

Step 1: Materials and Tools

There is now a full Bill of Materials and Sources list.

• 3D Printed parts

• Protoboard (1)

• TP4056 (1)

• JST XH Connectors (5 or 6)

• 1N5817 Diodes (3)

• SPDT PCB Switch (0 or 1)

• 18650 Battery (1)

• 18650 Battery Holder (1)

• Strong Cyanoacrylate glue (1)

• Hookup wire

• Solder and Iron

• Tinned wire (or diode lead cutoffs)

• 4G x 6mm stainless pan head self tapping screws (4)

• Male header pins (6)

• Sharp straight pick

Step 2: Building the Circuit

The curcuit has 2 variations: onboard PCB switch and a breakout for an external switch.

• Cut the protoboard to 71mm x 17mm with 28 x 6 holes showing

• Solder 2P (2) and 1P (2) male headers to undersind of TP4056

• Bend pins slightly to center of TP4056 so they match the protoboard spacing.

• Insert USB side of TP4056 into holes 12 from end of protoboard, ensuring pushed in to plastic collars on pins and solder off

• Solder JST XH sockets: 5 for onboard switch, 6 for external switch.

• Solder SPDT PCB switch (if using onboard switch)

• Place diodes on topside through holes, with cathode line closest to TP4056

• On underside, solder anode end of diodes to + on JST XH pins, and cathode end to IN+ on TP4056

• On underside, trace and solder - on JST XH (IN) pins to IN- on TP4056

• On underside, trace and solder B- and B+ on TP4056 to the edge of the protoboard

• On underside, trace and solder - on JST XH (OUT) pins to OUT- on TP4056

• On underside, trace and solder OUT+ on TP4056 to centerping on SPDT.

• On underside, trace and solder outer SPDT pin to + on JST XH (OUT) pins.

• If not using SPDT (alternative external switch breakout) solder to replacement JST XH pins instead (polarity observation not necessary).

Its been noted that the onboard USB charger on the TP4056 is not accessible with this layout; that will be addressed in the PCB version of this project.

Step 3: Assembling the Pieces

Before starting I suggest you verify the TP4056 and switch are working.

• Take the battery holder and route both wires through base hole on one end

• Then route those wires throgh the matching hole on the 3D printed base

• Align both bases, flats touching, and create pilot holes with sharp straight pick into battery holder through 4 corner holes

• Fix bases together with 4G x 6mm pan head screws (4)

• DRY RUN: place circuit into 3D printed base, and fit appropriate 3D printed lid; make minor mods fo a good fit and remove lid and circuit

• Solder battery + and - to B+ and B- rails on circuit with wires trimmed to good length for final assembly

• Place a good dob of hot glue in 3D printed base and place in circuit; whilst glue is hot dry fit lid moving the circuit to align with lid voids

• Allow glue to dry and remove lid

• Put drops of Cyanoacrylate on sides of lid where they will tough inside walls of base

• Fit lid aligning top surface with base walls top

• Add the appropriate label to fit the lid you have used

• Fit 18650 battery.

Step 4: Integrating Into Your Project

• Up to 3 solar panel circuits can be connected to the charge controller

• Ensure the voltage of each solar panel circuit is ~5V, and the total current of all circuits is 200mA to 300mA

• Estimate the power consumption of your needs and only use the second power output if is within range.

• If the power supply is concealed and not within easy reach, use the external switch breakout and place your own switch; be mindful to keep leads as short as possible.

Step 5: Next Steps

Look for the upcoming CYCLING HELMET SOLAR PANELS.

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