3.10 Inputs and Outputs

This page explains what each input and output function of the BMS does, when to use it, and how many inputs and outputs each board has. The contactor outputs and their wiring layouts are described in 3.8 Power Path.

Applies to

Boards: BMS1820, BMS3610, BCU2002, BMS1601, BMS1810.

3.10.1 How It Works

Fig.3.10.1: Input and Output Functions by What They Do

Inputs: INPUT n Assignment Outputs: OUT n Assignment Disable a path the input holds a path OFF Battery Output Disable DCHG Power Path Disable CHG Power Path Interlock Feed back a contact checked against the contactor state Main Contactor Auxiliary CHG Contactor Auxiliary DCHG Contactor Auxiliary Switch a path follow the charge and discharge path Main Contactor Output Pre Charge Contactor Output Charge Contactor Output Discharge Contactor Output Report a state signal only; no path changes Low SOC Limit-1 (≤15) Low SOC Limit-2 (≤5) Over Temperature Warning Cell Over Voltage Warning Cell Under Voltage Warning DCHG Under Temp Warning CHG Under Temp Warning External Led Functionality Always ON BMS controls the charge path and the discharge path Charge Power Path Control Discharge Power Path Control override controls: for testing only An input is active while its pin is pulled to ground. An active output is High (BMS1810: see Table.3.10.4); a relay connects COM to N.O. CHG and DCHG Contactor Auxiliary: BMS1810 only. DCHG Power Path Interlock is TBD. Blue labels are LiMon™ names.

  • Assignment: each output and each input has one function, set on the LiMon™ Peripheral tab with OUT n Assignment and INPUT n Assignment. Several outputs can have the same function.
  • Active input: an input is active while its pin is pulled to the ground of its port, on an isolated input the GND of that isolated port, for example by a closed switch or contact. An open input is inactive.
  • Active output: an active TTL or high-side output is High. An active relay connects COM to N.O. BMS1810 differs; see the note under Table.3.10.4.

3.10.2 Output Functions

Table.3.10.1: Output Functions

Function What it does How to use it
No Function The output stays inactive. Every output that is not used.
Main Contactor Output, Pre Charge Contactor Output, Charge Contactor Output, Discharge Contactor Output Switch the contactors of the power path. Choose them with the wiring layout in 3.8 Power Path.
Low SOC Limit-1 (≤15) Active while the SoC is at or below 15 %. Inactive as soon as the SoC is above 15 %. A low-battery lamp, or a signal that asks the system to reduce the load.
Low SOC Limit-2 (≤5) Active while the SoC is at or below 5 %. Inactive as soon as the SoC is above 5 %. A last signal that asks the system to stop in an orderly way.
Over Temperature Warning Active while the warning set by Over Temp. Warning is present (3.5 Temperature Limits). A cooling fan or a warning lamp.
Cell Over Voltage Warning Active while the warning set by O.V. Warning is present (3.3 Cell Voltage Limits). A signal that asks the charger to reduce the current.
Cell Under Voltage Warning Active while the warning set by U.V. Warning is present (3.3 Cell Voltage Limits). A signal that asks the system to reduce the load.
DCHG Under Temp Warning Active while the warning set by DCHG. U.T. Warning is present (3.5 Temperature Limits). A heater or a warning lamp.
CHG Under Temp Warning Active while the warning set by CHG. U.T. Warning is present (3.5 Temperature Limits). A heater, or a signal that asks the charger to wait.
External Led Functionality Flashes with the status LEDs of the board: one flash about every 2 s in normal operation; 3, 4 or 5 flashes while a long, mid or short button press waits for its confirmation. A lamp on the front panel of the system.
Always ON Active while the BMS runs; inactive after a shutdown. A signal that the BMS is running, or the supply of a small accessory.

Except for the contactor outputs, these functions only give a signal: they do not switch a path. The limits of 15 % and 5 % are not LiMon™ settings.

3.10.3 Input Functions

Table.3.10.2: Input Functions

Function What it does How to use it
No Function The input is ignored. Every input that is not used.
Battery Output Disable While the input is active, both paths are OFF, except that an active CHG Power Path Interlock keeps the charge path ON. The paths follow the BMS again as soon as the input is inactive. A stop signal from the system controller or a maintenance switch that must stop the whole battery.
DCHG Power Path Disable When the input has been active for 5 s, the discharge path is OFF. The charge path is not affected. The discharge path follows the BMS again as soon as the input is inactive. A signal that must stop the load but still allow charging, for example a key switch.
CHG Power Path Interlock Inactive: the charge path stays OFF. Active for 5 s: the charge path can switch ON and the discharge path stays OFF. The sense contact of the charge socket; see layout C in 3.8 Power Path.
Main Contactor Auxiliary Compares the auxiliary contact with the main contactor state and sets Main Contactor Malfunction when they disagree. A main contactor with an auxiliary contact; see 3.8 Power Path.
CHG Contactor Auxiliary, DCHG Contactor Auxiliary BMS1810 only. The same check for the charge or the discharge contactor; they set Charge Contactor Malfunction or Discharge Contactor Malfunction. A charge or discharge contactor with an auxiliary contact on BMS1810.
DCHG Power Path Interlock TBD. TBD.

When a disabling input releases the discharge path, the precharge runs again (3.9 Precharge). A disabling input does not count as a trip for Error Recovery Attempts.

3.10.4 Settings

Table.3.10.3: Input and Output Settings (LiMon™ Peripheral tab)

Setting What it does How to choose Unit Range Default
OUT n Assignment Output function per output. Table.3.10.1, on an output the board has (Table.3.10.4). list Table.3.10.1 No Function
INPUT n Assignment Input function per input. Table.3.10.2, on an input the board has (Table.3.10.4). list Table.3.10.2 No Function
Charge Power Path Control Override of the charge path: Automatic Control, Path Always ON or Path Always OFF. Automatic Control in service. list — Automatic Control
Discharge Power Path Control Override of the discharge path: Automatic Control, Path Always ON or Path Always OFF. Automatic Control in service. list — Automatic Control

The LiMon™ reference describes every field of the screen: 7.5 Peripheral Settings.

Override controls: these two settings are for testing, for example to check a contactor and its wiring on a bench.

  • Path Always ON: the path is ON whatever the protections, the faults and the input functions say. The events are still reported, and the precharge still runs on the discharge path.
  • Path Always OFF: the path is OFF whatever the BMS and the input functions say.
  • The setting stays: it is saved in the BMS and still applies after a restart.

Path Always ON overrides the protections

With Path Always ON nothing protects the path from over-voltage, over-current or over-temperature. Use it only on a test bench under supervision, and set Automatic Control again before the battery goes into service.

3.10.5 Inputs and Outputs per Board

The numbers in LiMon™ do not always follow the order of the names on the board. Use this table to find the pin. The values come from the schematics, the board pages and the firmware and have not been checked on a board. For an output, assign Always ON and measure which pin changes; for an input, pull a pin to the ground of its port and see which INPUT mark comes ON in Events › Pack Status.

Table.3.10.4: LiMon™ Numbers and Physical Inputs and Outputs per Board

Board LiMon™ name Board signal Connector · pin Type
BMS1820 OUT 1 High-side output (OUTPUT_0) P7 · 7 high-side switch
OUT 2 High-side output (OUTPUT_1) P7 · 8 high-side switch
OUT 3 High-side output (OUTPUT_2) P7 · 9 high-side switch
OUT 4 High-side output (OUTPUT_3) P7 · 6 high-side switch
OUT 5 Isolated output 1 (ISO_Filtered_OUT_1) P6 · 9 isolated TTL
OUT 6 Isolated output 2 (ISO_Filtered_OUT_2) P6 · 8 isolated TTL
OUT 7 Relay P12 · 1, 2 COM; 3 N.O.; 4 N.C. relay
INPUT 1 Isolated input 1 (ISO_Filtered_IN_1) P6 · 6 isolated logic input
INPUT 2 Isolated input 2 (ISO_Filtered_IN_2) P6 · 7 isolated logic input
INPUT 3 Isolated input 3 (ISO_Filtered_IN_3) P6 · 10 isolated logic input
BMS3610 OUT 1 High-side output (OUTPUT_2) P7 · 9 high-side switch
OUT 2 High-side output (OUTPUT_1) P7 · 8 high-side switch
OUT 3 High-side output (OUTPUT_0) P7 · 7 high-side switch
OUT 4 High-side output (OUTPUT_3) P7 · 6 high-side switch
OUT 5 Isolated output 1 (ISO_Filtered_OUT_1) P6 · 9 isolated TTL
OUT 6 Isolated output 2 (ISO_Filtered_OUT_2) P6 · 8 isolated TTL
OUT 7 Relay P12 · 1, 2 COM; 3 N.O.; 4 N.C. relay
INPUT 1 Isolated input 1 (ISO_Filtered_IN_1) P6 · 6 isolated logic input
INPUT 2 Isolated input 2 (ISO_Filtered_IN_2) P6 · 7 isolated logic input
INPUT 3 Isolated input 3 (ISO_Filtered_IN_3) P6 · 10 isolated logic input
BCU2002 OUT 1 Isolated Output 1 (OUT-1) 3 · 6 isolated TTL
OUT 2 High-Side Switch Output 1 (HSSO-1) 17 · 8 high-side switch
OUT 3 High-Side Switch Output 0 (HSSO-0) 17 · 7 high-side switch
OUT 4 High-Side Switch Output 2 (HSSO-2) 17 · 9 high-side switch
OUT 5 High-Side Switch Output 3 (HSSO-3) 17 · 6 high-side switch
OUT 6 Relay Output 18 · 1, 2 COM; 3 N.O.; 4 N.C. relay
INPUT 1 Isolated Input 1 (IN-1) 3 · 4 isolated logic input
INPUT 2 Isolated Input 2 (IN-2) 3 · 5 isolated logic input
BMS1601 OUT 1 ISO TTL Output 2 3 · 8 isolated TTL
OUT 2 ISO TTL Output 1 3 · 9 isolated TTL
OUT 3 Onboard relay No#1 6 · 3 COM; 5 N.O.; 4 N.C. relay
OUT 4 Onboard relay No#2 6 · 6 COM; 2 N.O.; 1 N.C. relay
INPUT 1 ISO TTL Input 1 3 · 7 isolated logic input
INPUT 2 ISO TTL Input 2 3 · 6 isolated logic input
INPUT 3 ISO TTL Input 3 3 · 10 isolated logic input
BMS1810 OUT 1 High-side output 1 (HP_OUT1) 9 · 3 high-side switch, 12 V
OUT 2 High-side output 2 (HP_OUT2) 9 · 2 high-side switch, 12 V
OUT 3 Output 1 (OUT-1) 10 · 9 open collector, 12 V pull-up
OUT 4 Output 2 (OUT-2) 10 · 8 open collector, 12 V pull-up
OUT 5 Relay 1 9 · 1 COM; 5 N.O.; 4 N.C. relay
OUT 6 Relay 2 17 · 1 or 2 COM; 3 N.O.; 4 N.C. relay
INPUT 1 Input 1 (IN-1) 10 · 6 optocoupler input
INPUT 2 Input 2 (IN-2) 10 · 7 optocoupler input

LiMon™ shows OUT 1–8 and INPUT 1–3 for every board. An assignment on a number that the board does not have does nothing.

This manual gives no current rating for the outputs. Check the load current with LiBat™ before you connect a contactor coil or another large load straight to an output.

The BMS1820 rows are for hardware v2.3, the BMS3610 rows for v1.1 the BCU2002 rows for v2.2 and the BMS1601 rows follow its pinout page. BMS1820 and BMS3610 have no pinout page yet, so their connectors are given by the P number of the schematic. OUT 1 and OUT 3 sit on swapped pins between BMS1820 and BMS3610.

The BMS1810 rows are for hardware v1.4.1. Their connector numbers are those of the pinout page: connector 9 is P12, connector 10 is P13 and connector 17 is P10 on the schematic. OUT 1–2 switch the 12 V of the board to the output. OUT 3–4 are open-collector outputs with a 10 kΩ pull-up to 12 V: an active output is Low and an inactive one is at 12 V. An input comes ON when its pin is connected to the ground pins of the same connector (10 · 1 to 4).

3.10.6 Checking the Result

  • Events › Pack Status shows INPUT-1 to INPUT-3 and OUT-1 to OUT-8. Close the contact on an input and check that its INPUT mark comes ON.
  • With DCHG Power Path Disable active for 5 s, Events › Pack Status shows DCHG Force OFF and the discharge contactor is open.
  • An OUT mark shows what the BMS commands, not what the wiring does. Check a status output with a multimeter or on the device it drives.
  • Charge Power Path Control and Discharge Power Path Control read Automatic Control before the battery goes into service.

3.10.7 Common Mistakes

  • The same input function on two inputs: only the input with the highest number counts, and the other one is ignored. Assign an input function to one input only.
  • An input function changed without a restart: the state of the old function can stay in effect, for example paths that stay OFF after Battery Output Disable was removed. Restart the BMS after you change an input function.
  • A normally closed contact on a disabling input: a closed contact is active, so the path stays OFF until the contact opens. Use a normally open contact.
  • Battery Output Disable expected to stop the charging with the charge cable plugged in: an active CHG Power Path Interlock keeps the charge path ON.
  • A Low SOC output expected to stop the discharge: it only gives a signal. The discharge path switches OFF at U.V. Protection (3.3 Cell Voltage Limits).
  • Path Always ON or Path Always OFF left set after a test: the setting stays after a restart. A path that never reacts to the system points to this setting.