This is a Battery Management System (BMS) board designed as an Arduino Uno shield. The BMS can handle up to 12 sieries connected cell modules and is fully programmable for any battery chemistry. The Arduino Uno is programmed to control an Linear Technologies LTC6804 Battery Monitor IC through the 4-wire SPI interface at pins 41-44. The arduino reads the data collected by the LTC6804, such as cell voltages, current and cell temperatures and also controls peripheral circuitry such as charge cutoff and discharge cutoff relays. R-C filters are provided for each cell monitoring input.

The schematic is provided in the figures. Analog inputs A2 - A5 are connected to the corresponding Arduino analog input pins, with +5 and ground also routed to each connector. A0 connects to a LEM hall effect sensor which outputs approximately Vin/2 at zero current where Vin is nominally 12 volts. A separate voltage divider connects to A1 which monitors the true Vin as a reference. Vin may vary depending on the state of charge of the external 12V supply. The relay drivers are controlled by the Arduino's digital pins 8 and 9. Drivers can handle up to 9 Amps, however mose relay coils will draw less than 1 Amp.

The BMS board is designed to be connected to an Arduino UNO as a standard shield. It draws power directly from the Arduino, which should be plugged in to a 12V supply.   The BMS board has input connectors for two temperature sensors and a LEM Hall effect current sensor. The board uses  TE/APM 5-103634-2  three position right angle header connectors for these sensor inputs. The sensor cables should mate to these headers with the pin definitions (gnd, +5v and signal) indicated on the circuitboard. There are optional slots on the circuitboard for two additional temperature sensor inputs and two general purpose input/outputs (GPIO). Temperature sensors are MPC9700 3-pin Thermistor ICs or similar: Datasheet The arduino code is calibrated for a  50 amp LEM HTB 50-P/SP5 current sensor.  Other current sensors can be used, but the code may need modification if the sensor has a different nominal current rating.  There are two relay control outputs which use TE/APM 103635-1 two position headers.  One relay header is for the charge relay and the other is for the discharge relay.  These can be repurposed for other uses in the arduino code.  The board supplies power to the relay coils with a maximum rated current of 9 amps, but this may be limited by your arduino power supply.  Note: powering the Arduino from USB cable will probably not provide enough current to keep the relay coils energized.  Battery sense wires plug into the top row of the 13 pin, 0.1 pin spacing header. Respect the indicated polarity when connecting the battery sense wires.  Reversing the polarity may cause permanent damage to the BMS board.

LTC6804 datasheet: 

http://cds.linear.com/docs/en/datasheet/680412fc.pdf

The Arduino BMS sketch and more detail can be found here: http://caditz.us/PowerElectronics/BMS_LTC6804

There is an optional passive balance board which will be posted separately. Cell voltages, current and temperatures can be monitored wirelessly using XBEE modules.