This is an Atmega 32U4 based Synchronous MPPT Buck Solar Charge Controller
Features:
- Programmable with Arduino IDE
- Input voltage 12 - 22V (36 cell solar panel)
- Output voltage 2.5 - 14.4V (single cell lithium up to 6 cell lead acid batteries can be directly charged)
- Simple MPPT (Maximum Power Point Tracking) solar charge controller for 18V solar panels
- Proper buck converter topology, which increases the current on the output side, not just PWM
- Sparkfun Pro Micro 5V, 16MHz or 3.3V, 8MHz (3.3v recommended, more efficient)
- ACS712 current sensor (5A version) on the output side
- Voltage dividers for voltage measurement on panel and output side
- Two N-channel mosfets, driven by IR2104 half bridge driver, inductor (synchronous buck converter, D5 increases efficiency)
- Third N-channel mosfet as efficient anti backfeed protection without the use of a lossy diode
- Supplied by the panel voltage, so it can't drain your battery during the night
- Working frequency 31.5kHz
- WARNING! This device is not intended to drive 5V USB devices directly. Do it at your own risk!
- Always use a regulated 5V USB adapter on the output! Otherwise, voltage glichtes may damage your USB device!
- This controller is COMMON NEGATIVE
- 4 operation modes: MPPT, CV, CC, Idle
- SD card data logger for time, voltage and current. You can import the txt files in Excel
- WARNING! Always adjust output voltage and output current limits according to your battery type, before you connect the battery
- Efficiency between 72% and 92%
New in V 1.0:
- Initial commit, tested with my 10W and 20W solar panels, charging my DIY USB power bank with 8 18650 cells in parallel. Two TP4056 lithium charger modules in paralel on the output
- An anti backfeed diode on the output is required, if you charge batteries directly! Otherwise, your low side mosfet may blow up!!
New in V 1.1:
- Anti backfeed diode is not required anymore, MOSFET Q1 added as anti backfeed protection. It is driven with 16V by a separate charge pump circuit (D3, D4, D6, C8)
- Direct charging tested with 6.6Ah, 12V Lead Acid battery and 4 18650 cells in parallel, charge current up to 3.8A
- Software changed: MOSFET Q3 protection (this is very critical, because it can short the battery to GND!)
- Freewheel diode D5 added to improve efficiency
- LM317T regulator replaced with a more efficient MP1584EN step down module
New in V 1.2:
- Optimized for 4.2V 1S LiPo 18650 direct charging
New in V 1.3:
- Display now using u8x8 instead of u8g2 in order to save flash memory
- Ah is displayed as well, not just Wh.
- Splash screen shows SW version
- Switchable display content, using Menu button
- Pot is used for manual / automatic MPPT tracking instead of output voltage adjustment
- tested with my 10W and 20W solar panels, charging my DIY USB power bank with 8 18650 cells in parallel. The TP4056 board is not used as chrarger anymore, just as BMS (overcharging, overdischarging, overcurrent). The 18650 cells are connected to the B+ and B- terminals, the charger and the USB aoutput stepup modules to the OUT+ and OUT- terminals. The output voltage is 4.2v , which is the maximum charge voltage of an 18650 cell.
To do:
- Adding a configuration menu, using the buttons
- Changing the inductor to allow 5A charge current
- Designing a proper PCB
Usage
See pictures
Also have a look at the pdf schematic.
(c) 2018 TheDIYGuy999