Lithiumate Lite Overview

General description of the digital BMS for EVs

back to top Block diagram

The BMS is powered:

  • By the 12 V from the ignition, when the EV is on
  • By the AC power whenever the EV is plugged into the wall

The BMS is connected to

  • The traction pack
  • The charger
  • The motor controller
Block diagram of a BMS in an EV Click picture to enlarge
Overall block diagram

back to top Battery Management


  • Measures and reports the cell voltages and temperatures in up to 8 banks of cells in a battery pack
  • Measures and reports the battery pack current (bidirectional load current up to 900 A; charger current up to 30 A)


  • Calculates and reports the State Of Charge of the battery pack


  • Balances the pack
    • Dissipative (passive) balancing
    • Top balance, voltage based
Battery pack Click picture to enlarge
BMS in an application


  • Turns off charger if any cell voltage exceeds a maximum, or the charging current is excessive
  • Requests a reduction of motor drive if the battery is nearly empty
  • Requests that motor controller be turned off if any cell voltage drops below a minimum, or the discharging current is excessive
  • Disables charging and/or discharging if any cell's temperature is outside a range
  • Disables charging and discharging if any cell board or bank stops reporting
  • Prevents driving off when the vehicle is still plugged into the AC outlet

back to top Charger interface

AC power connector

  • AC Line input from the vehicle's AC plug (85 to 260 Vac)
  • LED to indicate that AC power is present

Charger current sensor

  • 30 Adc, charger DC output current sensor

No connector assembly required:

  • AC power connector is 2-piece, screw clamp, terminal block
  • Charger current sensor uses ring terminals mounted on screw terminals
AC interface block diagram Click picture to enlarge
Charger interface

back to top Vehicle traction interface

Ignition power input

  • 12 V nominal, 50 mA nominal (no external loads)
  • LED to indicate that Ignition power is present

Cable mounted current sensor

  • Ready to plug-in
  • Bidirectional, 900 A max

"Discharge OK" line, normally at 12 V, open when battery cannot deliver current

  • Wire to the key input of the motor controller, or use to drive the main contactor
  • Wire to a "Ready" lamp on dashboard
Vehicle traction interface Click picture to enlarge
Vehicle traction interface

"Low Battery" line, normally at 12 V, open when battery charge is low

  • Wire to the "Valet" input of the motor controller, to reduce available drive
  • Wire to a relay to add resistance to the throttle, to reduce its range
  • Wire to a "Reserve" lamp on dashboard

"Throttle Reduce" output, to reduce throttle range (2 or 3-wire pot, not HEPA)

  • Insert in the "Wiper" line, between throttle and motor driver (for 3-wire throttle, a resistor must ve added)
  • Wire to a relay to add resistance to the throttle, to reduce its range
  • Isolated, for compatibility with motor drivers with pack referenced throttle

"Charge OK" line, normally at 12 V, open when battery cannot accept current

  • Wire to the "Regen Enable" input of the motor controller, to disable regen
  • Wire to brake pedal pot, to disable regen

"Fault" line, normally open, grounded when a fault is detected

  • Wire to a "BMS fault" lamp on dashboard
  • LED to indicate that there is a fault

No connector assembly required:

  • Load current sensor comes with a connector
  • Control connector is 2-piece, screw clamp, terminal block

back to top Traction pack interface

The BMS uses cell boards mounted directly on prismatic cells

  • Up to 200 cells in series in a pack
  • Divided into banks
  • Each bank betweem 2 to 20 cells in series, recommended (users have used up to 25 cells)
  • Cells directly in parallel count as one cell and use just inbe cell board
  • Each bank has one positive end cell board, one negative end, and the rest are mid bank cell boards
  • Each cell board measures its cell's voltage and temperature
  • Posive end and negative end cell boards include an isolator, to isolate the high voltage of the pack from the 12 V supply
Cell connections Click picture to enlarge
Block diagram of cell connections

Bank connectors

  • Uses up to 4 each, RJ45 cables
  • Each RJ45 cable connects the master to a breakout
  • Each RJ45 cable and breakout handles 1 or 2 banks
  • A breakout has 4 cables: two for positive end cell boards, 2 for negative end cell boards

No connector assembly required:

  • Bank connections use off-the-shelf shielded RJ45 modular Ethernet cables (0.5 to 4 meters, as appropriate for the application)
  • Complete modular cables are readily available from numerous sources
  • Breakout at other end of modular cable is fully assembled
Traction pack interface Click picture to enlarge
Traction pack interface

back to top Monitoring and configuration

17 status LEDs on master

  • "AC Power in": lit if powered by the AC line
  • "Ignition power": lit if powered by the Ignition line
  • "Charge OK": lit if charging is enabled
  • "Discharge OK": lit if discharging is enabled
  • "Warning": lit if the battery is nearly empty
  • "Fault": lit if a fault was detected
  • "Status": normally fully lit; in case of fault it flashes a code for the fault
  • An LED for each bank indicates the satus of the communications for that bank
  • Two LEDs by the USB connector flash when data is transmitted and received
Status LEDs Click picture to enlarge
Status LEDs

Three gauges on dashboard

  • Drives standard fuel gauges (emulates fuel tank "sender")
    • Configurable to match sender's characteristics (min and max resistance, direction)
    • May be configured to drive a 5 V full scale meter
  • Drives meters: battery current and voltage
    • For 5 V full scale meters
    • Full scale value configurable to match full scale on meter's face plate
    • Designed to operate with popular Westach gauges
  • Every controller LED function may be duplicated on dashboard with 12 V lamps
Ammeter, voltmeter, SOC meter Click picture to enlarge
Ammeter, voltmeter, SOC meter

Graphics User Interface

  • Computer based monitoring and configuration
  • USB port for easy interface to the computer
    • Uses a standard USB cable (no adapter dongle is required)
  • Windows™ user interface
    • Basic configuration takes only 4 steps
    • One screen displays the complete status of the battery and the BMS
GUI screen shot Click picture to enlarge
GUI application screen

back to top Front panel

AC power connector:

  • AC power in, 85 to 265 Vac

USB connector:

  • For connection to PC, during set-up and for troubleshooting

Current sensor connectors:

  • Battery current sensor screw terminals, 30 A max
  • Connector for prewired 900 A bidirectional load current sensor
Front panel Click picture to enlarge
Front panel

Bank connectors:

  • 4 connectors, each for 2 banks
  • Each connector has 2 LEDs, one for ach bank, to indicate its status
  • Uses standard shielded RJ45 modular cables

Control connector: (clockwise from top)
Two-piece terminal block, screw clamps

  • Meter outputs:
    • Pack voltage meter, configurable range, for 5 Vfs voltmeter
    • Pack current meter, configurable range (may go negative), for 5 Vfs voltmeter (may be bidirectional)
    • Pack SOC meter, emulates fuel gauge sender, configurable resistance, or for 5 Vfs voltmeter
  • Power outputs:
    • 12 V when powered by the AC line (0.3 A max)
    • 12 V when powered either way (1 A max if powered from the Ignition line, 0.3 A max if powered by the AC line)
    • 5 V when powered either way (50 mA max)
  • Power input:
    • 12 V from the Ignition line
  • Control outputs:
    • Charge OK: normally 12 V, open if charging is not allowed
    • Discharge OK: normally 12 V, open if discharging is not allowed
    • Fault: normally open, 12 V in case of fault
    • OK: normally 12 V, open in case of fault
    • Warning: normally open, 12 V at the end of battery charge
    • Throttle: normally open, gradually lower resistance at the end of battery charge


In this page:
Block diagram
Battery Management
Charger interface
Vehicle traction interface
Traction pack interface
Monitoring and configuration
Front panel
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