Charge Controller for 12 cell Lifepo4 batteries
Output voltage can be adjusted between 0 and 110% with voltage between TRM and -S on CN1: Output Voltage = (Voltage between TMR and -S / 2.5) * 5V
Output current can be measured between CB adn -S on either CN1 or CN2. Ouput current: 1Vcb = 0A, 0Vcb = 50A, -1Vcb = 100A Iout = 50 * (-Vcb + 1) Required input impedance > 500kOh Max current 120A ???
Circuit: Set TRM to default ouput of 4.2V, allow output range of 0 to 4.2V Invert and shift current sense from -1 to 2V, to 0V to 2.4V Over current feedback, with max current and trickle current Isolated signalling, either capacitive or dedicated IC
TESTING: * Double check default output voltage of 4.2V * Double check current graph/equation
Results: With 0 current, CB measuers 1.221V 1A , 1.5V 2A, 1.13 3A, 1.098 4A, 1.069 5A, 1.04 SHOULD REQUIRE DIRECT TURN OFF?
BOARD REVISION:
- ADD 3.3V test point
- ADD potentiometer for adjusting current and voltage set points
- change plus and minus inputs on op-amp B (because CB voltage decreases as voltage rises)
- add reverse input protection diode
- make sure trickle disable is pulled low
- add some leds for signalling
HOW FLASH EFM8 MCU:
https://www.silabs.com/community/mcu/8-bit/knowledge-base.entry.html/2015/06/08/how_to_use_efm8_star-8aHu https://www.allaboutcircuits.com/projects/custom-pcb-design-with-an-efm8-microcontroller/