The Basic equalizer schematic is built around a PIC 16F876 microcontroller. The microcontroller check the adjustement key, controls the LCD display and switch on the single cell discharge. The power supply (12VDC typical) is filtered and reduced to 5V using a 7805 general purpose linear regulator. From the 5VDC is created, using a small DC/DC converter a 15VDC power supply for mosfet gates biasing, in order to turn on the gate of the "last" cell discharger is necessary at least a potential of 3-4 volts above the last cell voltage or 10V+4V=14/15V. If the user connects a power supply of 15VDC the small DC/DC converter can be not mounted, but the user must shorts the LM7805 pin 1 (input) to the DC/DC converter pin 3 (output) in order to replace the DC/DC converter. A supply voltage above 20V can over-bias the mosfets gates with possible transistor damage.
The voltage from the cell pack is routed to the PIC A/D converter using an ADG508 analog multiplexer and 6 buffers (OP290 or LM358). The PIC calculates the differences from each battery tap to the following for single cell voltage controlling and for cut off voltage checking.
The discharge process is controlled by the PIC microcontroller using a series of mosfet driven by an individual optocoupler for gate voltage shifting (this barrier of optocoupler is not strictly necessary, the voltage shifting can be also achieved with a bjt transistor...).
The discharge current is controlled by the 6.8 Ohm resistor that give a (1.2/7=0.17A) typical current that decrease with the cell voltage decreasing. The LCD display plus the leds are for cell voltage visualization and for cell discharge status observing.