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The pack is kept whole. Its original BMS stays in place. A BMS-EV controller reads the pack's CAN bus, translates it, and hands the data to a hybrid solar inverter.
The short version. A complete EV battery pack, with its original BMS retained, is connected to a hybrid solar inverter through a BMS-EV controller that translates the pack's CAN bus into the inverter's protocol. The original safety architecture — cell balancing, over/undervoltage cutoff, over-temperature cutoff, contactor control — remains under the manufacturer's BMS. The inverter sees a "battery" that speaks a familiar protocol (Pylontech, BYD, or similar) and charges or discharges it based on PV, house load and grid conditions.
The inverter's MPPT tracks the PV array. Surplus power (PV minus house load) flows into the battery. The pack BMS reports SoC and charge-current limit; the controller relays these to the inverter, which throttles when the pack asks it to.
House load exceeds PV output. The inverter draws from the battery until the pack's SoC reaches a configured floor (typically 10–20% depending on chemistry) or the BMS signals discharge cutoff.
The controller sends periodic keep-alive frames on the vehicle CAN bus so the pack BMS does not enter deep sleep. Contactors may be open (isolated) or held closed at trickle current, depending on the setup.
Hybrid inverters with backup capability disconnect from the grid on outage and continue supplying the house from battery. This requires an ATS or the inverter's built-in EPS output.
The controller exposes pack state through several channels:
bms/<device_uid>/status, bms/<device_uid>/spec_data, bms/<device_uid>/balancing_data. Integrates with any MQTT-aware system.Full pack-specific wiring diagrams are on each battery's dedicated page — Tesla Model 3, BMW i3, Nissan Leaf, VW MEB, and others.
No. The complete pack is used as-is. The controller connects to the pack's external CAN bus and control pins — the same pins the vehicle used.
The controller detects loss of pack heartbeat, opens contactors, and signals fault to the inverter. The inverter stops charge/discharge. This is the intended safety response.
Yes, if the vehicle BMS publishes per-cell voltages on CAN (most do). The controller relays those to the Web UI and MQTT. Some vehicles group cells into module summaries only.
No — the controller impersonates whatever battery protocol the inverter already supports (Pylontech is the most common target). No inverter firmware change is needed.
Two packs of the same voltage can be paralleled through their contactors, but each pack must have its own BMS-EV controller or one controller with a multi-pack firmware build. Contact us for multi-pack builds.
Yes — a small standby load (typically under 5 W) keeps the vehicle BMS awake. If the system is fully idled for extended periods (weeks) the controller can be configured to power down the pack.
If the hybrid inverter is a backup-capable model (EPS output or ATS), the inverter isolates from the grid and continues to supply the house from the battery until SoC reaches the configured floor.
Yes, with an off-grid or hybrid inverter configured in off-grid mode. Some inverters (Deye, Sol-Ark) support both modes; others (SMA Sunny Boy Storage) are grid-tied only.