BMS · 5 min

Dilithium BMSC vs a wrecked OEM pack BMS

The BMS you buy for a conversion is not the factory board that came on the wrecked pack.

What the BMSC is

Dilithium Design’s BMSC is a standalone 24-cell BMS: processor and measurement board in one box. Each measurement board has two LTC6811s (up to 24 cells, 10 thermistors). Up to three BMSS satellites add 24 cells each — 48, 72, or 96. Multiple systems can watch larger packs.

Manual v3.1 (Jan 2024) and the Thunderstruck shop: cells about 8 times a second, LVC/HVC alerts on CAN or a cell loop (LP1/LP2, 200 mA, dry contact or open collector). Passive balance: 24 Ω / 1 W resistors, about 170 mA at 4 V, only above a configurable voltage. Default CAN is 250 kbps, 29-bit. Serial for setup. Firmware v3.1.2+ can command a single TSM2500 over CAN. That path does not speak J1772.

Catalog: https://evengineeringlab.com/parts

What the factory pack BMS is

Tesla Model S/X modules ship with a factory BMS board on the module. Shops sell replacement tap boards so your BMS can read the cells. Stealth EV: some modules have tap wires soldered to those boards and will not take the replacement. Thunderstruck’s Leaf VCU does not control the Nissan BMS or PDU — they point you at a separate BMS.

The BMSC CAN dictionary is Dilithium’s (0x01dd0001 and friends), not Tesla or Leaf OEM CAN. Do not expect the factory computer to run a TSM2500.

What you actually do

  1. Count series cells. One BMSC is 24. Over that, add satellites.
  2. Wire the tap harnesses (or Tesla tap boards + Dilithium harness). Test them before you put HV on the pack. Thunderstruck includes a 12-cell test board with the BMSC.
  3. Set LVC, HVC, balance, thermistors. Lock the config.
  4. Put it on the same CAN as the charger (or the EVCC). Alerts are how charging stops.

This page does not invent Tesla module counts or drop-in wiring for a specific wrecked pack. The Tesla module diagrams on EV West’s BMSC page are shop docs, not this site’s spec.

What people get stuck on

A complete Tesla S pack BMS is not drop-in. To keep the factory pack happy you would have to simulate a pile of CAN and other inputs. Forum advice is an external BMS after you open the pack. https://www.diyelectriccar.com/threads/experience-with-the-simp-bms-for-tesla-modules.204808/

Do not run HV cell-tap wires front to back. Dilithium satellites keep that as a comms cable. Tesla modules are 6s; some BMS tap groups are 12. https://www.diyelectriccar.com/threads/sanity-check-for-orion-bms-cell-taps-and-tesla-batteries.207703/ Unused taps on a 12-pin loom are a first-build failure: 0 V readings, then dead modules. https://www.diyelectriccar.com/threads/dilithium-bms-and-5-tesla-model-s-module-troubleshooting.211006/ Thunderstruck: taps have to be in ascending voltage order. https://www.diyelectriccar.com/threads/thunderstruck-mcu-for-bms.208316/

LVC/HVC is not set-and-forget. HVC is a message to the charger to stop. The charger has to listen. BMS HVC is the backstop. https://www.diyelectriccar.com/threads/thunderstruck-bms-settings-help.202255/

Sources

  • https://www.thunderstruck-ev.com/images/companies/1/BMS/BMSC-Manual.pdf
  • https://www.thunderstruck-ev.com/bms-controller.html
  • https://evwest.com/dilithium-bms-controller-thunderstruck-bmsc
  • https://evwest.com/support/BMS_2-2_Quick_Start_Guide.pdf
  • https://evwest.com/tesla-model-sx-battery-module-bms-connectivity-and-fuse-protection-pcb-boards
  • https://stealthev.com/product/tesla-model-s-x-battery-module-bms-cell-tap-board/
  • https://www.thunderstruck-ev.com/dilithium-vcu.html