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Pairing a used BMW i3 22, 33 or 42 kWh HV pack with the SOFAR HYD 5-20KTL-3PH three-phase hybrid inverter series using BYD Battery-Box protocol emulation.
Direct answer. A complete BMW i3 HV pack (all generations: 22, 33 and 42 kWh; 260–395 V operating range) is compatible with the SOFAR HYD 5-20KTL-3PH three-phase hybrid inverter series, which accepts a battery DC input of 180–800 V. The lower end of the BMW i3 discharge curve (260 V at deep discharge) falls below the SOFAR minimum, so the BMS-EV controller applies a conservative discharge cut-off at 300 V — this must be verified against the specific SOFAR firmware revision before commissioning. Communication is via BYD Battery-Box HV protocol emulation on the SOFAR CAN port.
| Component | Status | Notes |
|---|---|---|
| BMW i3 22 kWh (60 Ah) pack | Yes | NMC, 260–395 V; usable capacity ~18 kWh |
| BMW i3 33 kWh (94 Ah) pack | Yes | NMC, 260–395 V; usable capacity ~28 kWh |
| BMW i3 42 kWh (120 Ah) pack | Yes | NMC, 260–395 V; usable capacity ~36 kWh |
| SOFAR HYD 5-20KTL-3PH | Yes | 180–800 V DC; requires firmware verification of low-voltage cutoff |
| SOFAR HYD 3-6K-EP (single-phase) | No | LV battery only (~48 V) |
| SOFAR HYD ESI (all-in-one) | No | Integrated LV battery, no HV external interface |
| Model | AC power | Phase | DC battery range | MPPT |
|---|---|---|---|---|
| HYD 5KTL-3PH | 5.0 kW | 3-phase | 180–800 V | 2 |
| HYD 6KTL-3PH | 6.0 kW | 3-phase | 180–800 V | 2 |
| HYD 8KTL-3PH | 8.0 kW | 3-phase | 180–800 V | 2 |
| HYD 10KTL-3PH | 10.0 kW | 3-phase | 180–800 V | 2 |
| HYD 15KTL-3PH | 15.0 kW | 3-phase | 180–800 V | 2 |
| HYD 20KTL-3PH | 20.0 kW | 3-phase | 180–800 V | 2 |
The BMW i3 pack operates between 260 V (0 % SoC, deep discharge) and 395 V (100 % SoC). Nominal voltage is approximately 350 V. The SOFAR HYD-3PH battery input specifies 180–800 V — the BMW i3 sits at the very bottom of this window.
Practical operation: the BMS-EV controller reports a discharge cut-off SoC that keeps pack voltage above 320 V, which corresponds to approximately 15 % SoC on a 33 kWh pack. This preserves battery health and stays comfortably inside the SOFAR window. At the top end, 395 V full charge is well below the 800 V inverter maximum, so no over-voltage risk exists.
SOFAR HYD-3PH firmware supports the BYD Battery-Box HV protocol on its dedicated battery CAN port. The BMS-EV controller emulates a BYD HVS module stack:
| Data | Source (BMW i3 BMS) | Target (BYD HV frame) |
|---|---|---|
| Pack voltage | 0x112 byte 0–1 | 0x110 byte 0–1 |
| Pack current | 0x112 byte 2–3 | 0x110 byte 2–3 |
| SoC | 0x1F0 byte 4 | 0x150 byte 0 |
| Max cell voltage | 0x2A2 byte 0–1 | 0x210 byte 0–1 |
| Min cell voltage | 0x2A2 byte 2–3 | 0x210 byte 2–3 |
| Max temperature | 0x2FC byte 3 | 0x220 byte 0 |
| Charge current limit | Computed by BMS-EV (chemistry + T) | 0x130 byte 4–5 |
| Discharge current limit | Computed by BMS-EV (chemistry + T) | 0x130 byte 6–7 |
| Alarm flags | 0x2C0 bit-mapped | 0x360 byte 0–3 |
Engineering values below are examples. Final conductor cross-section and protective-device 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).
The 42 kWh (2018+) pack offers the best capacity-to-price ratio and has better cell chemistry (Samsung SDI 120 Ah). The 33 kWh (2016–2018) is a close second and is currently more available on the used market. The 22 kWh (2013–2016) is functional but usable capacity after aging is often below 15 kWh.
No. BMS-EV supplies configured controllers for packs bought as complete units from EV recyclers. Mechanical extraction requires a certified HV workshop.
Not on a single DC input. The HYD-3PH commercial models support one battery bank. For two packs, either use two separate inverters (one per pack) or wire them in parallel on the DC bus with strict SoC matching and a single BMS-EV controller in master/slave configuration.
The SOFAR opens its battery contactor when battery voltage drops below its lower limit and reports a fault. The BMS-EV controller anticipates this and stops requesting discharge current before the SOFAR trips — provided the "Battery Cutoff SoC" is set to at least 15 % in the SOFAR installer menu.
Yes. SolarMAN shows pack V, I, SoC, and daily energy correctly. The pack appears as "BYD Battery-Box HVS" — cosmetic mismatch only.
No. The BMS-EV controller drives the BMW i3's original precharge resistor and main contactors. The SOFAR inverter's role is limited to DC bus current control after the pack has been closed.
On a HYD 10KTL-3PH with a 33 kWh BMW i3 pack, measured round-trip AC-in to AC-out is approximately 88–90 %. The BMW pack itself is highly efficient (~97 %); most of the loss is inverter conversion.