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Tesla Model 3 Battery with SOFAR HYD Inverter

SOFAR HYD 5KTL–20KTL-3PH three-phase hybrid inverters are one of the most economical and well-supported ways to reuse a Tesla Model 3 or Model Y battery pack for residential and small-commercial energy storage. This page documents the exact firmware, wiring, CAN protocol translation and commissioning procedure used in a BMS-EV deployment.

What works, at a glance

• All four Model 3 pack variants: LR NCA 75 kWh, SR+ NCA 55 kWh, SR+ LFP 60 kWh, Highland LR 78 kWh.
• Model Y AWD / LR / Performance (shared pack).
• SOFAR HYD 5KTL-3PH, 6KTL-3PH, 8KTL-3PH, 10KTL-3PH, 15KTL-3PH, 20KTL-3PH.
• Grid codes: VDE-AR-N 4105, VDE 0126-1-1, EN 50549-1, CEI 0-21, G99, NC RfG.
• Backup operation (island mode) fully supported on HYD-3PH via the built-in EPS output.
• Time-of-use scheduling, peak shaving, self-consumption optimisation — controlled by the inverter, not the controller.

Supported SOFAR models and power ranges

Minimum SOFAR firmware required: ARM V010 / DSP V010 (June 2024 or later). Older firmware treats the BYD HVS protocol as v1.0 and will refuse to start the battery if it reports more than 60 kWh nominal.

Per-variant compatibility (BMS-EV firmware profile detail)

Pack revisions are grouped for firmware-selection purposes. Specify the exact vehicle year and pack part number at ordering so BMS-EV can flash the correct firmware branch and set chemistry-specific limits (NCA vs LFP taper points, cell voltage windows).

Battery voltage range — Tesla 270–410 V vs SOFAR HYD 180–800 V DC absolute

Two ranges to distinguish per SOFAR HYD 5–20KTL-3PH datasheet:

Important distinction: the absolute range is the voltage window at which the inverter will charge or discharge at all. The full-power range is the voltage window at which the inverter delivers its nameplate AC power. Below the full-power voltage lower bound, power derates linearly with battery voltage. Confirm the exact derate curve for your specific firmware revision by requesting the current SOFAR HYD datasheet from the local SOFAR distributor.

A Tesla Model 3 LR NCA pack (270–410 V operating) sits within the absolute range of every HYD model, but only within the full-power range of HYD 5KTL, 6KTL, 8KTL and 10KTL variants. For HYD 15KTL, Tesla NCA at low SoC (~300 V) is at the low edge of the full-power window. For HYD 20KTL, Tesla NCA below ~400 V (roughly 50 % SoC) will run derated — practically meaning less peak grid-injection headroom during morning solar spikes when the pack is partially charged.

Practical Tesla LR NCA behaviour: the pack sits at ~350 V nominal, ~278 V at OEM-defined 0 % SoC and ~410 V at 100 % SoC. Practically:

• The Tesla BMS never lets the pack fall below 3.0 V/cell → 288 V pack — but the BMS-EV controller enforces a stationary lower limit of 3.4 V/cell → 326 V pack, then reserves the 326–350 V band as a "reserve tank" that only the inverter's forced discharge for a self-consumption event can touch.
• Working window (BMS-EV default): 350 V (0% usable) to 400 V (100% usable). This maps to 30%–95% of the pack's raw voltage window, avoiding the aggressive top and bottom that accelerate degradation.
• LFP variant (212–383 V range) is narrower — SOFAR HYD accepts the full LFP pack voltage window (212–383 V) since it starts at 180 V. Usable capacity is limited by the OEM BMS's deep-discharge protection, not by the inverter. In practice, BMS-EV limits usable capacity to ~55 kWh out of the 60 kWh nominal, cycling between OEM-defined minimum SoC (~2.9 V/cell) and 100% SoC (3.65 V/cell max charge for LFP). LFP flat voltage curve means SoC and pack voltage are only weakly correlated — coulomb counting is used instead.

CAN protocol mapping — Tesla native to BYD Battery-Box HVS

The BMS-EV controller subscribes to Tesla's internal CAN messages and re-emits them on the inverter-side bus using the BYD Battery-Box HVS dictionary, which SOFAR HYD implements. Selected mappings:

Charge and discharge current limits are computed by the BMS-EV controller from the Tesla-reported cell voltage headroom and temperature. Rule of thumb defaults, adjustable via the controller's serial console:

• Charge current derates linearly from full rate (SOFAR HYD-3PH input: 50 A max at 355 V nominal, ~17.5 kW) at 3.9 V/cell to 0 A at 4.10 V/cell.
• Discharge current derates from full rate (SOFAR HYD-3PH battery input: 25 A per channel × 2 channels = 50 A max total continuous DC current per SOFAR datasheet, ≈ 17.5 kW at 355 V nominal) to 0 A between 3.4 V/cell and 3.2 V/cell. The SOFAR HYD 5-20KTL-3PH has two independent battery input channels (each rated 25 A / ~10 kW) that can be paralleled or used with two separate battery banks; the BMS-EV controller feeds both channels from a single Tesla pack via a common bus bar.
• Both limits are clamped to zero if any temperature sensor reads < 0 °C (charging blocked) or > 55 °C (both blocked).

Wiring architecture

Installation requirements

• HV DC cabling. 25 mm² fine-strand copper (H1Z2Z2-K solar cable or IEC 62930/EN 50618 equivalent) for HYD 5–10KTL; 35 mm² for 15–20KTL. Orange sheath, temperature rating 105 °C, UV-stable if any run is outdoors. PV1-F (older cable standard) may not meet 1500 V DC insulation and is not recommended for new installations.
• DC disconnect and fusing (example values). A DC isolator (Santon, Kraus & Naimer, ABB OTDC160) plus HRC gPV fuses sized for maximum inverter current. Final conductor and fuse sizing must be calculated for the actual pack, maximum current, cable length, installation method, ambient temperature and applicable local standards (IEC 60364-7-712, VDE-AR-N 4105, NEC 690.).
• Grounding. Pack case bonded to the main equipotential bar with 16 mm² green/yellow. Inverter chassis grounded independently.
• Communication cabling. Twisted pair CAT6 or dedicated CAN cable, maximum length 5 m between pack and controller, 3 m between controller and inverter. 120 Ω terminator at the controller side.
• Auxiliary 12 V supply. A small 230 V AC → 12 V DC 3 A power supply (Meanwell HDR-15-12 or similar), UPS-backed. Loss of 12 V opens the pack contactors.
• Enclosure and clearances. The SOFAR HYD needs 300 mm clearance on all sides and 500 mm above for heat dissipation. Keep the Tesla pack at least 1 m from the inverter to prevent EMI coupling.
• Coolant. If sustained discharge above 15 kW is expected, connect the pack's factory coolant ports to a small 12 V pump and a passive radiator. Below 15 kW average, the pack's thermal mass is sufficient without active cooling for residential duty cycles.

Commissioning sequence

1. With DC isolator OPEN, verify HVIL loop closed (multimeter continuity through the LV connector), verify pack terminal voltage is within 280–410 V.
2. Power on the BMS-EV controller (12 V aux). Wait ~5 s for boot. Green LED should blink at 1 Hz indicating CAN traffic on the pack side.
3. Configure the SOFAR HYD via SolarMAN app: Settings → Battery → Type = "BYD HVS", Capacity = value shown by the controller's config screen (typically 130 Ah for LR NCA, 170 Ah for LFP).
4. Close the DC isolator. The controller will command precharge, then main contactors. Full HV should appear at the inverter DC terminals within 6 s.
5. Trigger a self-consumption cycle: cover the PV panels, force a load. Verify AC output tracks the battery discharge, SoC decreases smoothly, no CAN error codes on the inverter display.
6. Charge from grid (SolarMAN → Force charge) to 100% SoC. Verify the charge current tapers correctly above the upper voltage threshold applicable to your pack chemistry: ~4.05 V/cell for NCA/NMC (Model 3/Y LR NCA, Model S/X NCA); ~3.45 V/cell for LFP (Model 3 SR+ LFP; upper OEM charge limit is 3.65 V/cell, so tapering should be visible well before that). Applying an NCA taper point to an LFP pack under-utilises the pack; applying an LFP taper point to an NCA pack risks over-charge.

Known limitations

• SOFAR firmware older than ARM V010 refuses the BYD HVS profile for > 60 kWh nominal capacity. Update firmware first via USB stick, not via SolarMAN OTA (which is unreliable for HYD-3PH).
• Backup / EPS output is limited to unbalanced single-phase loads on some HYD firmware. Confirm the EPS certification for your inverter serial before relying on it.
• Battery calibration is one-shot at commissioning. If the Tesla pack is deeply discharged before SOFAR sees it, SoC display can be off by up to 5 percentage points until a full charge–discharge cycle completes. Start at > 40% SoC when commissioning.
• Cold weather. Below 0 °C the pack refuses to charge, and BMS-EV mirrors this to SOFAR as CCL = 0. If your installation regularly sees pack temperatures below 0 °C, install pack heaters or increase enclosure insulation.
• Grid outage and precharge. After a grid outage in island mode, the SOFAR HYD holds its DC link partially charged. Re-precharge is handled transparently, but a full grid restore + island transition sequence can take up to 15 s.
• No dual-battery aggregation. SOFAR HYD-3PH accepts one battery bank per inverter. To combine two Tesla packs, use two inverters on the same three-phase busbar with parallel-mode enabled.

Frequently asked questions