System wiring

Tips on connecting an Elithion Lithiumate™ BMS to other components

These sample schematics may offer suggestions on how to use an Elithion BMS in your application.

In general, the Lithiumate BMS is compatible with DC motor controllers and AC motor inverters.

The most basic way of allowing the BMS to control a motor driver is by havimg it drive a contactor that is connected between the battery and the motor driver. This, however, results in a sudden loss of power when the battery is discharged, which in a vehicle is not desirable, and downright dangerous.

The better approach is a two step one:

1. Make the motor controller abide to the BMS's request to reduce battery current as the battery is near depletion
2. Finally, when the battery is empty, make the motor controller do an orderly shut down upon the BMS's request

There are 3 ways to reduce the motor drive as the battery is near depletion:

• Human intervention (unreliable): let the driver see a display or hear a sound controlled by the BMS, and rely on the driver to slow down the vehicle
• Step reduction: when the battery reaches a certain state of depletion, engage a low power mode, to make the driver suddenly aware of the conditions, and not allow excessive battery drain
• Gradual reduction: as the battery becomes more and more depleted, gradually reduce the battery current that the motor driver is able to use

Very few motor drivers have the provisions to enable such control.

In most cases, the way to let the BMS control the motor driver is by reducing the range of the throttle pot, electrically:

• For step control, let the BMS control the addition of a resistor across a 2-wire pot when the battery is nearly empty.
• For gradual control, power a 3-wire throttle pot from the DCL ouput, which is normally at 5 V, but is reduced at the end of the battery charge.

• Azure DMOC

The most basic way of allowing the BMS to control a charger is with an AC relay on the charger's input, driven by the HLIM output of the BMS. The HLIM output polarity must be set so that the HLIM is normally grounded.

This method works with any charger.

The relay must have the following specifications:

• Coil voltage: DC rated, equal to the available supply voltage, which must not exceed the BMS controller's Absolute maximum ratings
• Coil resistance: such that the resulting current does not exceed the BMS controller's Absolute maximum ratings
• Contact voltage rating: AC rated for the AC line voltage
• Contact current rating: rated for carrying and braking the maximum input AC current of the charger at full power
• Regulatory rating: for the location of its use

You must decide which relay works in your application.
Questions to ask are:

• The load that the charger will place on the line supply: resistive or inductive? start up current? continuous current? voltage range? does it have a control input with which you will shut it down before you turn off the AC power?
• How you want to mount the relay: soldered? socket? PCB? surface mount? chassis mount? DIN rail mount?
• What kind of environment the relay will be in: dry? wet? spray? any corrosive gases? ambient temperature range? any unusual atmospheric pressure?
• What supply voltage is available to drive the relay: 12 Vdc? 24 Vdc? 48 Vdc?
• Where will the system be used: what local and national regulations must it meet?

Only after those questions are answered can an appropriate relay be recommended.

As you can see, there are hundreds of permutations. We are not able to offer suggestions for all those permutations.

Here is just one example, with a system with the following specifications:

• 12 V supply
• 115 Vac line voltage
• 1500 W Power Factor Corrected charger
• Used in the US
• Automotive environment, in the passenger cabin

Then the requirements for the relay are:

• Coil voltage: 12 Vdc
• Coil resistance: >= 10 Ohm
• Contact voltage rating: 125 Vac rated
• Contact current rating: 15 Aac resistive load, carrying, braking
• Regulatory rating: UL
• -40 to +85 °C
• Sealed not necessary

WARNING The suggestions below are for the particular example system described above; they are believed to be correct, but not guaranteed to be so.

Examples of parts that will meet those ratings include:

• Panasonic HL1-H-DC12V-F, socket mounted relay, 20 SPDT, 125 Vac 15 Aac
• Tyco T9AP5D52-12, chassis mounted relay, SPDT, 240 Vac, 20 Aac
• TT Electronics OSSRD0002A, chassis mounted solid state relay, SPST-NO, 250 Vac, 15 Aac

Many other methods of connecting a charger to the BMS exist, based on the specifications of the charger and the user's preference.

Here are six examples, which emphasize the method to power the BMS whenever the AC source is present, even during those times that the BMS is turning off the charger.
They all show a single pole relay. You may repolace the relay with an SSR (Solid State Relay). In some cases a 2 pole relay would be required.

The first and last example above use a a power supply to power the BMS whenever plugged in for charging.
The requirements for such a supply are:

• Input voltage same as all possible AC input voltages; for example, a 90 Vac to 265 Vac switching supply can handle both 110 and 220 V line inputs
• 12 Vdc output
• At least 150 mA out

For example, this universal input, 12 V output, switching power supply meets the above requirements: ST Micro's SPAC265BC12P0.30

WARNING These are just examples. You must decide what circuit is appropriate in your application.

• Brusa NLG5 series
• Delta Q charger
• Manzanita Micro PFC series
• Zivan NGx series

For electric vehicles, it is best to warn the driver as the battery gets low, before totally shutting down the drive.

One way of doing so is to reduce the range of the throttle gradually as the battery nears the end of its charge.

For a 3-wire throttle, this can be done by wiring one of the leads to the BMS controller instead of to the motor controller.

The resistor values may have to be changed to match the voltages at the 2 ends of the throttle pot when it's connected normally to the motor controller.

For EV conversions, you may be able to have the BMS controller drive the vehicle's fuel gauge directly.

• The BMS controller has an SOC output
• Many vehicles have a fuel gauge that is connected to 12 V at one end, and through a resistive sensor ("sender") in the fuel tank, to ground

Gauge:

• 127 Ohm
• 90 mA to show full
• 35 mA to show empty

Sender:

• 4 Ohm when full
• 107 Ohm when empty

BMS controller's SOC output (Control connector, pin 15):

• 5 V when full
• 0 V when empty

You can use this circuit to adapt between the two.

• Sample schematic 1 (pdf):
  • CAN bus, but analog throttle
  • Battery: 72S1P Li-Ion cells in 6 banks; 12 V aux battery
  • charger: Brusa NLG5
  • Motor: Azure DMOC motor inverter and AC motor (included contactors
  • RM Michaelides RM1001 CAN display
  • Small DC fan, cable mounted current sensor, loss of isolation test