Wiring & installPin-outs SizingInteractive

Orion BMS 2 · Wiring & Installation

Everything you need at the bench: how to size and order the BMS, the interactive Main I/O pin-out, output electrical limits, and the safety-critical voltage-tap rules - distilled from Ewert's wiring manual. This is a companion; follow the full manual for every safety-critical detail.

Read firstNever wire or alter battery/tap wiring while the tap connectors are plugged into the BMS - remaining wires can become live through the internal diodes, risking injury, fire and (uncovered) BMS damage. Keep taps disconnected until wiring is complete and verified.

Cell range

24-180

With remotes

324

Max pack

800 V

Main I/O pins

CAN interfaces

Tap wire

22 AWG

Safety - read this first

The essentials from the manual's safety section. Integration must be carried out by a qualified person familiar with lithium-battery safety.

Sizing & ordering

Order for the number of cell-tap positions, not just cells. Fuses, safety disconnects and high-impedance busbars mid-pack may force you to skip positions - so size up when unsure. Available in 12-cell increments.

How many cells in your pack?

–

Enter a cell count for a starting BMS size.

A larger unit can run fewer cells (a 108-cell unit works with as few as 4), giving wiring flexibility. Confirm the exact size against the manual and your fuse/disconnect layout.

Connectors & pin-outs

The pin-out sheet shows the wire side of each connector. Search or filter the Main I/O pins; tap a row for detail. Click any diagram to enlarge.

Connector locations on the 180-cell Orion BMS 2 unit - Thermistor, Main I/O, status LED, five cell-tap group ports and ground lug — Connector locations on the 180-cell Orion BMS 2 - Thermistor & Main I/O connectors, status LED, five cell-tap group ports (1-3 … 13-15) and ground lug. Click to enlarge.

Orion BMS 2 pin-out diagrams — Full pin-out sheet · wire side · © Ewert Energy. Click to enlarge.

Output electrical limits

Enable / safety outputs are watchdog-backed and can drive a contactor; multi-purpose outputs are signal-level only. * via an external relay/driver.

Wiring the voltage taps

The highest-risk part of the install. Read the full "Wiring Voltage Taps" section of the manual before you start.

WarningNever alter any battery wiring - including tightening cell terminals - while the BMS is connected. Disconnect the cell-tap connectors first, and do not reconnect until all wiring is complete and the harnesses have been tested.

Harness & colour codeOrion 2 must use gold-plated tap harnesses (never mix with tinned contacts). Cell group 1 = orange, group 2 = red, group 3 = yellow; cell-group ground wires are black. Cells are numbered from pack-negative upward, one tap per cell plus one negative tap per 12-cell group.

Orion BMS 2 · 23-cell battery tap connections23S lithium pack · tap wiring map, balance-connector pinout & voltage reference

Legend

Pack positive (+)

Balance taps 1–11

Balance taps 12–23

Pack negative (−)

⊖Current sensor

Notes

Taps are measured relative to Pack Negative (Pack−).
Connect each tap wire to the corresponding point between cells as shown.
Pack− must go through the current sensor.
Do not connect anything to unused tap inputs.

Voltage reference (vs Pack−)

Tap 0 (Pack−)0 V

Tap 11 × Vcell

Tap 22 × Vcell

……

Tap 23 (Pack+)23 × Vcell

Vcell = nominal cell voltage · e.g. 3.2 V for LiFePO₄

Orion BMS balance connector (24-pin)

PinTapConnects to

1Tap 0 (Pack−)Pack negative (through current sensor)

2Tap 1Between Cell 1 (+) and Cell 2 (+)

3Tap 2Between Cell 2 (+) and Cell 3 (+)

4Tap 3Between Cell 3 (+) and Cell 4 (+)

5Tap 4Between Cell 4 (+) and Cell 5 (+)

6Tap 5Between Cell 5 (+) and Cell 6 (+)

7Tap 6Between Cell 6 (+) and Cell 7 (+)

8Tap 7Between Cell 7 (+) and Cell 8 (+)

9Tap 8Between Cell 8 (+) and Cell 9 (+)

10Tap 9Between Cell 9 (+) and Cell 10 (+)

11Tap 10Between Cell 10 (+) and Cell 11 (+)

12Tap 11Between Cell 11 (+) and Cell 12 (+)

13Tap 12Between Cell 12 (+) and Cell 13 (+)

14Tap 13Between Cell 13 (+) and Cell 14 (+)

15Tap 14Between Cell 14 (+) and Cell 15 (+)

16Tap 15Between Cell 15 (+) and Cell 16 (+)

17Tap 16Between Cell 16 (+) and Cell 17 (+)

18Tap 17Between Cell 17 (+) and Cell 18 (+)

19Tap 18Between Cell 18 (+) and Cell 19 (+)

20Tap 19Between Cell 19 (+) and Cell 20 (+)

21Tap 20Between Cell 20 (+) and Cell 21 (+)

22Tap 21Between Cell 21 (+) and Cell 22 (+)

23Tap 22Between Cell 22 (+) and Cell 23 (+)

24Tap 23 (Pack+)Pack positive (+)

Example · LiFePO₄

Nominal cell (Vcell)

3.2 V

Full pack (23S)

73.6 V

Tap 1

3.2 V

Tap 11

35.2 V

Tap 12

38.4 V

Tap 23 (Pack+)

73.6 V

Always verify tap wiring before powering the BMS. Incorrect wiring can permanently damage the BMS.

Connecting an open-drain output to a relaySample schematic · drive a contactor or relay from a BMS enable output

Open-drain output sinks current to ground when active (ON). Maximum sink current per output: 175 mA.

Outputs

To Load / System (Switched, N.O.)

To Load / System (Common)

The BMS open-drain output turns the relay ON by sinking current through the coil to ground.
Use a flyback diode (D1) across the coil to protect the BMS output from voltage spikes.
Ensure the relay coil voltage matches your supply (+5 V to +24 V).
Maximum coil current (and BMS output sink current) must not exceed 175 mA.

Recommended diode

1N4148, 1N5819 or similar · cathode (stripe) to +V

Fusing the tapsInternal BMS fuses protect against over-/reverse-voltage but not tap-to-tap shorts. If external cell-tap fuses are used, place them as close to the cell terminal as possible, rate them ≤ 5 A and for the full DC working voltage. Series resistors are not permitted as tap current-limiters. Verify every tap with the validation tool or a multimeter before connecting the BMS.

Reference topics

Condensed guidance on the concepts you'll meet while wiring. Search to filter.

Documents & downloads

The full manuals and related interactive guides. Links open in a new tab.

SOFTWAREOrion BMS 2 UtilityConfigure & program the BMS · needs a CANdapterWindows Linux ZIP Beta

PDFWiring & installationThis guide (original PDF)Download GUIDEOperations guideTheory · limits · fault codesOpen GUIDEQuick-start guide8-step interactive setupOpen PDFOperations manualFull BMS operationDownload PDFPurchasing guideSize & specify the BMSDownload GUIDEOrion BMS 2 guideInteractive system builderOpen