# EVMG: Chevy Volt 16S Module & 48S Pack BMS Tap Pinout Specification

## 1. Overview & Connector Identification
Each Gen 1 Chevrolet Volt (LG Chem) lithium module contains 16 series-connected lithium pouch cell pairs ($16\text{S}$). 
The module top cover houses a recessed **16-pin dual-row rectangular connector socket** (formerly connecting to GM OEM BICM boards). 
Uninsulated cell tabs run directly to these connector pins, providing access to individual cell voltages without dismantling the physical cassette.

```
          OEM 16-PIN RECESSED CONNECTOR SOCKET (TOP VIEW)
          ┌───┬───┬───┬───┬───┬───┬───┬───┐
  ROW B   │ 9 │ 10│ 11│ 12│ 13│ 14│ 15│ 16│  (Pins 9 to 16)
          ├───┼───┼───┼───┼───┼───┼───┼───┤
  ROW A   │ 1 │ 2 │ 3 │ 4 │ 5 │ 6 │ 7 │ 8 │  (Pins 1 to 8)
          └───┴───┴───┴───┴───┴───┴───┴───┘
               ▲ Key Notch / Latch Tab
```

---

## 2. 16S Cell Tap Sequence & Voltage Mapping (Per Module)

> [!CAUTION]
> Always verify sequential potential with a digital multimeter referenced to Module Negative ($C_0$) **before** connecting an aftermarket BMS.
> Nominal cell voltage is $3.65\text{V}$; fully charged cell voltage is $4.15\text{V}$.

| Header Pin | Signal Name | Cell Monitored | Nominal Voltage (vs. B-) | Full Charge Voltage (vs. B-) | Wire Color Standard |
| :--- | :--- | :--- | :--- | :--- | :--- |
| **Pin 1** | **$C_0$ (B-)** | Module Negative Stud | $0.00\text{V}$ (Reference) | $0.00\text{V}$ | Black |
| **Pin 2** | **$C_1$** | Cell 1 Positive Tap | $+3.65\text{V}$ | $+4.15\text{V}$ | Brown |
| **Pin 3** | **$C_2$** | Cell 2 Positive Tap | $+7.30\text{V}$ | $+8.30\text{V}$ | Red |
| **Pin 4** | **$C_3$** | Cell 3 Positive Tap | $+10.95\text{V}$ | $+12.45\text{V}$ | Orange |
| **Pin 5** | **$C_4$** | Cell 4 Positive Tap | $+14.60\text{V}$ | $+16.60\text{V}$ | Yellow |
| **Pin 6** | **$C_5$** | Cell 5 Positive Tap | $+18.25\text{V}$ | $+20.75\text{V}$ | Green |
| **Pin 7** | **$C_6$** | Cell 6 Positive Tap | $+21.90\text{V}$ | $+24.90\text{V}$ | Blue |
| **Pin 8** | **$C_7$** | Cell 7 Positive Tap | $+25.55\text{V}$ | $+29.05\text{V}$ | Violet |
| **Pin 9** | **$C_8$** | Cell 8 Positive Tap | $+29.20\text{V}$ | $+33.20\text{V}$ | Gray |
| **Pin 10**| **$C_9$** | Cell 9 Positive Tap | $+32.85\text{V}$ | $+37.35\text{V}$ | White |
| **Pin 11**| **$C_{10}$**| Cell 10 Positive Tap | $+36.50\text{V}$ | $+41.50\text{V}$ | Pink |
| **Pin 12**| **$C_{11}$**| Cell 11 Positive Tap | $+40.15\text{V}$ | $+45.65\text{V}$ | Light Blue |
| **Pin 13**| **$C_{12}$**| Cell 12 Positive Tap | $+43.80\text{V}$ | $+49.80\text{V}$ | Light Green |
| **Pin 14**| **$C_{13}$**| Cell 13 Positive Tap | $+47.45\text{V}$ | $+53.95\text{V}$ | Tan |
| **Pin 15**| **$C_{14}$**| Cell 14 Positive Tap | $+51.10\text{V}$ | $+58.10\text{V}$ | Purple/White |
| **Pin 16**| **$C_{15}$**| Cell 15 Positive Tap | $+54.75\text{V}$ | $+62.25\text{V}$ | Red/White |
| **M6 Stud**| **$C_{16}$ (B+)**| Module Positive Stud | $+58.40\text{V}$ | $+66.40\text{V}$ | Orange/White |

*(Note: In some Volt sub-assembly revisions, thermistor lines $T_1$ and $T_2$ are placed on Pins 15–16 with $C_{15}$–$C_{16}$ routed directly through the external busbar lugs. Validate pin voltages with a multimeter prior to final pinning).*

---

## 3. 48S Total Traction Pack Interconnection

When the three modules are connected in series inside the luggage boot:
* **Module 1 (Ground Potential):** Cells 1 to 16 ($0.0\text{V}$ to $65.6\text{V}$)
* **Module 2 (Mid-Pack Potential):** Cells 17 to 32 ($65.6\text{V}$ to $131.2\text{V}$)
* **Module 3 (High-Side Potential):** Cells 33 to 48 ($131.2\text{V}$ to $196.8\text{V}$)

```
[PACK NEGATIVE - 0V]
        │
   ┌────┴───────────────────────────┐
   │ MODULE 1 (16S: 0V to 65.6V)    │ ─── Harness 1 (Taps 1–16)  ───┐
   └────┬───────────────────────────┘                                │
        │ (Series Busbar Link)                                       │
   ┌────┴───────────────────────────┐                                │
   │ MODULE 2 (16S: 65.6V to 131.2V)│ ─── Harness 2 (Taps 17–32) ───┼──> [ ORION BMS 2 ]
   └────┬───────────────────────────┘                                │    (48-Channel Master)
        │ (Series Busbar Link)                                       │
   ┌────┴───────────────────────────┐                                │
   │ MODULE 3 (16S: 131.2V to 196.8V│ ─── Harness 3 (Taps 33–48) ───┘
   └────┬───────────────────────────┘
        │
[PACK POSITIVE - 196.8V MAX] ───> [ NEMA Disconnect Switch ] ───> [ 300A Fuse ] ───> [ Contactor ]
```

---

## 4. BMS Hardware Safety Interlock Wiring

```
                         [ BMS SAFETY SHUTDOWN LOOPS ]

 1. CHARGE OVERVOLTAGE CUTOFF (Elcon 2kW Charger Interlock):
    BMS Charge Enable Pin (Relay NO)
         │
         ├───> [+12V Aux] ───> [BMS Internal Relay] ───> [Elcon Enable Pin #3]
                                                            │
    (If any cell > 4.15V, BMS drops relay -> Elcon charger stops instantly)

 2. LOW-VOLTAGE / OVER-TEMP DISCHARGE CUTOFF (Albright SW180 Contactor):
    BMS Discharge Enable Pin
         │
         ├───> [Ignition 12V Switch] ───> [BMS Enable Relay] ───> [Albright Contactor Coil]
                                                                     │
    (If any cell < 3.10V or Temp > 48°C, contactor opens -> motor power removed)
```