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Tesla Model 3 Battery for Home Energy Storage

A complete Tesla Model 3 (or shared Model Y) battery pack is one of the most widely available high-voltage second-life storage options in Europe. This page documents the pack architecture, CAN protocol, contactor sequence, and the exact hybrid inverters we support through the BMS-EV controller.

Can a Tesla Model 3 battery be used for home storage?

Yes. Tesla Model 3 packs are structurally well suited to stationary second life. The pack is a sealed, liquid-cooled aluminium enclosure with four (Standard Range) or four (Long Range) internal modules of 21-70 or 2170 cylindrical cells, an internal HV junction with contactors and precharge, and a dedicated Battery Management Board (BMB) per module reporting to a central Battery Management System (BMS) computer on the top of the pack. All safety functions — cell overvoltage, undervoltage, overtemperature, isolation loss detection, contactor control — remain executed by the factory Tesla BMS. The BMS-EV controller does not attempt to replace those functions; it observes the CAN traffic that the BMS already produces, wakes the BMS by asserting the "vehicle is present" signals, and re-encodes the read-out values for the inverter. This approach preserves the OEM-engineered safety architecture end-to-end, which is a key structural difference from DIY BMS retrofits that require validating a new safety envelope.

Typical remaining state of health for a Model 3 pack aged 4–7 years is reported at 88–94% in independent Tesla fleet studies (Recurrent, Geotab, EV Health / Battery.io datasets). LFP packs from 2021 onwards have shown SoH above 95% after 200 000 km of vehicle use in the same datasets. Individual pack behaviour varies with charging history, ambient temperature and cycle depth — always verify SoH before purchase. For a residential energy budget of 10–18 kWh per day, one Model 3 pack covers 3–6 days of autonomy.

Supported Tesla Model 3 battery packs

The BMS-EV firmware covers every Model 3 pack variant sold in Europe and North America, plus the shared Model Y platform which uses the same electrical architecture.

• Model 3 Long Range (LR) 2018–2022, NCA chemistry — 75 kWh gross / 74 kWh usable, 355 V nominal (Tesla spec), 96S46P (4 416 cells of 21-70 format). Operating range: 270–410 V. This is the classic long-range pack, the most abundant on the used market.
• Model 3 Standard Range Plus (SR+) 2019–2020, NCA chemistry — 55 kWh gross / 50 kWh usable, 355 V nominal (Tesla spec), 96S31P. Operating range: 270–410 V.
• Model 3 SR+ LFP (Made in China) 2021+ — 60 kWh gross / 55 kWh usable, ~340 V nominal (LFP 3.2 V/cell × 106s, per batterydesign.net teardown; Tesla '400 V architecture' spec). Operating range: 265–387 V (2.5–3.65 V/cell). Higher cycle life (~4 000–6 000 full cycles), less capacity per volume.
• Model 3 Performance — same 75 kWh LR pack, identical electrical interface, different motor pairing (irrelevant for stationary reuse).
• Model 3 Highland (2023 refresh) LR — updated 78 kWh pack, same 96S topology, refined BMS firmware. Supported from BMS-EV firmware 9.3.0 onwards.
• Model Y AWD / LR / Performance — shares the Model 3 LR 75 kWh pack casing dimensions and electrical interface. Fully compatible.
• Model Y LFP RWD — shares the SR+ LFP pack architecture.

Battery specifications table

Original Tesla BMS: what is retained

Inside the pack there are four Battery Management Boards (BMB), one bonded to each of the internal modules, and one central Battery Management System (BMS) computer bolted on the top plate near the HV junction box. This assembly is left intact.

• Cell voltage measurement. Each BMB measures the voltage of every cell group in its module and reports over an internal isolated bus to the central BMS. Sampling rate: ~10 Hz.
• Temperature measurement. 12 NTC thermistors are distributed across the modules, plus additional sensors on the busbars. Read at 1 Hz.
• Passive balancing. Each cell group has a bleed resistor controlled by the BMB. Balancing runs whenever the pack is above ~90% SoC and cell delta exceeds 30 mV.
• Contactor control. Two main contactors (+ and −) plus a precharge contactor with a precharge resistor. The BMS decides when to close them based on isolation check, cell voltages, temperature and HVIL loop continuity.
• Isolation monitoring. A high-impedance measurement continuously checks that neither HV rail is bonded to the pack case. Isolation loss below the OEM threshold opens the contactors.
• HVIL (High Voltage Interlock Loop). A low-voltage series loop through every HV connector cover. Breaking the loop (e.g. someone unplugs a connector) immediately opens the contactors.

The BMS-EV controller never commands cell balancing, current limits or contactor closure directly. It only observes the CAN traffic and injects the wake / heartbeat frames the pack expects from the rest of the vehicle.

CAN communication

The Model 3 pack exposes an internal CAN bus on the low-voltage connector on the top of the pack. Electrical parameters:

• Bit rate: 500 kbit/s standard CAN 2.0B.
• Termination: 120 Ω at each end of the twisted pair. In the vehicle, one termination is inside the pack and the other in the vehicle harness. When redeploying, add one 120 Ω terminator at the BMS-EV controller side.
• Protocol: Tesla proprietary CAN, publicly reverse-engineered by the open-source EV battery reuse community (Battery-Emulator, SimpBMS, TeslaJs) and independently reimplemented in the BMS-EV controller firmware. Key message IDs read by BMS-EV controller include: 0x212 (BMS state, isolation, contactor state, HV status), 0x229 (BMS heartbeat with checksum), 0x252 (regen/discharge power limits), 0x292 (SoC min/max/average/UI, temperature %), 0x2D2 (min/max cell voltage, charge/discharge current limits), 0x312 (thermal management, pack temperatures), 0x332 (brick voltage extremes, temperature sensor bricks), 0x352 (energy metrics: nominal full pack energy, remaining, ideal, charge-to-complete), 0x392 (module type, pack mass, platform max bus voltage), 0x3D2 (lifetime energy counters), 0x20A (contactor states), 0x2B4 (DCDC LV/HV bus voltages). Full frame set reference: dalathegreat Battery-Emulator TESLA-BATTERY.cpp.
• Wake sequence. The pack expects a 12 V wake signal on a dedicated pin plus periodic CAN traffic from the "vehicle control" node. The BMS-EV controller applies the wake and then heartbeats every 100 ms.
• Contactor close request. After wake, the BMS performs its own self-test (typically 3–6 seconds). Once ready, it accepts a contactor close command over CAN. The precharge relay closes first, waits for the DC-link capacitors on the inverter side to charge to within 3% of pack voltage, then the main contactors close.

Contactors, precharge, HVIL and isolation

The Model 3 pack contains its own precharge network — this is important because most hybrid inverters expect the battery to arrive already at HV, without external precharge circuitry. Sequence during a normal power-up:

1. BMS-EV controller receives 12 V auxiliary power and starts its firmware.
2. Controller asserts the pack wake signal and begins CAN heartbeat.
3. Pack BMS boots, self-tests, verifies HVIL continuity and isolation.
4. Controller sends "contactor close" request over CAN.
5. Pack closes negative contactor, then precharge relay. HV rises to inverter DC-link over ~500 ms.
6. Pack closes positive contactor, opens precharge relay. Full HV available.
7. Controller starts publishing normalised battery data on the inverter-side CAN.

Any single failure — HVIL break, isolation drop, cell overvoltage, overtemperature, communication timeout — causes the pack to open its contactors within <100 ms without needing controller intervention.

Compatible hybrid inverters

BMS-EV controller compatibility

The Tesla Model 3 firmware profile is one of the earliest and most stable in the BMS-EV firmware family. Every controller shipped since April 2024 supports Model 3 LR NCA by default; LFP support was added in firmware 8.6.0 (September 2024); Highland refresh support in firmware 9.3.0 (June 2026). Every unit is flashed at the shop with the specific inverter profile the customer selected — the same physical hardware ships with SOFAR firmware, Deye firmware, GoodWe firmware, etc., differing only by the encoding layer.

Hardware highlights: ESP32-S3 dual-core MCU with Flash Encryption enabled, isolated dual CAN transceivers (TCAN1042 or MCP2562FD), 12 V wake output rated 500 mA, opto-isolated HVIL passthrough, aluminium enclosure 150 × 100 × 40 mm, DIN-rail or wall mount.

Known limitations

• LFP packs have a different cell count (106S vs 96S). Voltage window is lower (212–383 V) — some inverters with a hard 350 V minimum will not start from a deeply discharged LFP pack. Bring the pack to at least 20% SoC before first commissioning.
• Highland (2023+) refresh uses a slightly updated CAN dictionary. Firmware older than 9.3.0 will connect but will not report the "hot-swap ready" and "reserve capacity" fields correctly. Always update the controller before installing a Highland pack.
• Structural pack (Model Y made in Texas/Berlin, 4680 cells) is not yet supported by BMS-EV — the internal architecture is different (structural cell-to-pack) and the CAN dictionary has not been fully mapped. Follow the changelog for updates.
• No fast-charge input. The pack's Supercharging DC input is disconnected during stationary use. Charge and discharge always go through the main HV terminals via the inverter, with power limited by the inverter, not by the pack.
• Coolant. The pack's cooling loop must be filled and pressurised even in stationary use if operating above 20 kW average or in ambient temperatures above 30 °C. A simple 12 V pump plus a passive radiator is sufficient.
• Weight. 478 kg concentrated in a 2.1 × 1.5 m footprint. Floor loading must be verified — a slab or concrete garage floor is fine, but suspended wood floors in older buildings may not be.

Installation example — typical residential 75 kWh setup

The reference residential installation shipped by BMS-EV partners in Poland, Germany and the Netherlands. Engineering values below are examples — final cable, fuse and disconnect sizing must be calculated for the actual pack, inverter, cable length and applicable local standards:

• Battery: Tesla Model 3 LR NCA 75 kWh, 2020 salvage, 92% SoH verified with UDS diagnostic.
• Controller: BMS-EV pre-configured for SOFAR HYD 10KTL-3PH.
• Inverter: SOFAR HYD 10KTL-3PH three-phase hybrid, 10 kW AC, DC input 180–800 V.
• PV: 12 kWp roof array on two MPPT strings.
• HV DC cabling: 25 mm² fine-strand copper, DIN VDE 0100-712 compliant, orange sheath, HV warning labels every 500 mm.
• Enclosure: IP54 metal cabinet, floor mounted in unheated garage, class A fire barrier between cabinet and house wall.
• Ventilation: passive louvres top and bottom of cabinet; 12 V axial fan on 30 °C thermostat.
• Fusing (example values): 200 A DC fuse in the positive rail immediately at the pack (sized for the Tesla pack's own maximum continuous discharge current of ~350 A), plus a separate fuse rated for the specific inverter's DC input at the inverter side (e.g. SOFAR HYD-3PH accepts 50 A max continuous per its datasheet — a 63 A gPV fuse is typical there). HRC gPV type. Final fusing must be calculated for the specific pack, inverter, cable length, ambient temperature and applicable local standards (IEC 60364-7-712, VDE-AR-N 4105, NEC 690).

Typical daily behaviour: PV covers ~90% of annual household demand of 14 kWh/day. Pack cycles at ~15% DoD daily, projecting well over 20 years of calendar life before hitting the 80% SoH end-of-life criterion.

System architecture diagram

Frequently asked questions