Comprehensive reference tables and technical definitions for bidirectional energy (V2H, V2X, V2L), automotive BMS units, communication protocols, and solar storage integration.
Two ways EV batteries power homes:
1. In-Vehicle V2H: The car remains parked on your drive and feeds power backwards through a bidirectional wall charger (via CHAdeMO or CCS ISO 15118-20) into your house consumer unit.
2. Second-Life Stationary Storage: A salvaged traction battery pack (e.g. from an i3, Leaf, Bolt, or VW ID) is permanently installed in an outbuilding. An open-source Battery-Emulator speaks the car's native CAN bus to wake the battery and commands standard domestic hybrid inverters (Deye, Solis, Victron) to cycle the pack.
How electrical energy flows between the electric car battery, home appliances, consumer unit, and the national grid.
| Acronym | Full Name | Power Flow | Typical Power | Standards & Hardware | Primary Application & Second-Life Role |
|---|---|---|---|---|---|
| V2H# | Vehicle-to-Home | Car → House | 5 kW – 11.5 kW | CHAdeMO DC / CCS ISO 15118-20 / Hybrid Inverter |
Powers the residential distribution board (consumer unit) to run household circuits during peak rate hours or power outages.
Second-life: The primary goal of running salvaged 40–80 kWh EV packs with Battery-Emulator and hybrid inverters.
|
| V2L# | Vehicle-to-Load | Car → Device | 1.8 kW – 3.6 kW | Onboard 230V/120V socket or Type 2 charge port adapter |
Powers standalone electrical appliances (tools, camping gear, kettles, emergency freezer).
Limitation: Operates as an independent islanded socket; cannot safely connect to home wiring without a manual transfer switch.
|
| V2G# | Vehicle-to-Grid | Car → Grid | 5 kW – 22 kW | G98/G99 grid-certified inverter + Smart export meter |
Synchronized power export back into the public electricity network to support grid stability.
Financials: Generates revenue by selling stored off-peak energy during evening wholesale price spikes.
|
| V2X# | Vehicle-to-Everything | Umbrella | Flexible | ISO 15118-20 / CHAdeMO protocols |
The collective industry standard that encompasses V2H, V2L, V2G, V2B (Building), and V2V (Vehicle).
Protocols: Requires bidirectional vehicle firmware, bi-directional charger, and smart communication.
|
| V2B# | Vehicle-to-Building | Car → Facility | 10 kW – 50+ kW | 3-Phase Commercial Inverter + Building Management System | Commercial peak-shaving for offices and factories using company fleet vehicles to reduce maximum demand tariffs. |
| V2V# | Vehicle-to-Vehicle | Car → Car | 3 kW – 11 kW | V2L adapter to EVSE mobile charger or direct DC transfer | One EV directly rescue-charging another stranded EV on the roadside without an external generator. |
Original manufacturer battery computers, CAN speeds, frame IDs, and how they interface with open-source Battery-Emulator firmware.
| BMS Unit | Manufacturer & Models | Bus & Baud Rate | Cyclic CAN Frame IDs | Wake Method & Second-Life Compatibility |
|---|---|---|---|---|
| Nissan LBC# | Nissan Leaf (ZE0, AZE0, ZE1), e-NV200 | EV-CAN (500 kbps) | 0x1DB, 0x1DC, 0x55B, 0x5BC, 0x5C0 |
Woken via 12V ignition line. Battery-Emulator speaks native EV-CAN, reads all 96 cell voltages, and operates internal contactors without opening the case. |
| BMW SME# | BMW i3 (60/94/120 Ah), i4, iX3, 330e/530e PHEV | PT-CAN / K-CAN (500 kbps) | 0x1FA, 0x2FF, 0x13E, 0x3EB, 0x3CA |
Speicher-Management-Elektronik. Requires a 33 Ω interlock resistor across HVIL and wake-up line. Battery-Emulator transmits cyclic keep-alives. |
| Ford/GM BECM# | Chevy Bolt EV, Ford Lightning, Volvo XC40 | HS-CAN4 / GMLAN (500 kbps) | 0x30E, 0x312, 0x316, 0x40E9 (Bolt) |
Battery Energy Control Module. Manages cell balancing over CSC slave boards. Battery-Emulator handles contactor precharge sequence. |
| VW J840 (MEB)# | VW ID.3, ID.4, ID.5, Cupra Born, Skoda Enyaq | Hybrid-CAN (500 kbps, 29-bit extended) | 0x1B50E000, 0x1B50E001, 0x1B50E002 |
Master MEB battery computer. Reads 7 to 12 modular sub-packs. Requires extended 29-bit CAN identifiers. |
| BYD Blade BMS# | BYD Atto 3, Dolphin, Seal | EV-CAN (500 kbps) | 0x438, 0x43A, 0x444, 0x36D |
Controls 126s to 172s cell-to-pack LFP Blade configuration. Supported via Battery-Emulator with web-based cell balancing UI. |
| Tesla BMS# | Tesla Model 3, Model Y, Model S, Model X | Vehicle / Powertrain CAN (500 kbps) | 0x212, 0x252, 0x352, 0x102, 0x116 |
Integrated into the pentagon/pyramid high-voltage junction box. Supported via Battery-Emulator (Model 3/Y) or SimpBMS/Open-BMS (Model S modules). |
How high-voltage battery storage connects to home solar inverters, measuring devices, and electrical distribution.
| Component / Mode | Operating Range / Specs | Function & Role in Home Storage | Second-Life Suitability & Notes |
|---|---|---|---|
| HV Hybrid Inverter# | 150 V – 650 V+ DC 5 kW – 12 kW AC |
Directly connects to whole intact EV battery packs. Converts DC solar and battery power into 230V/400V AC household power. | Recommended: Allows using intact EV packs (BMW i3, Leaf, Bolt, ID.3) without opening or rewiring dangerous module internals. Examples: Deye HV, Solis HV, FoxESS. |
| LV (48V) Inverter# | 40 V – 60 V DC 3 kW – 15 kW AC |
Standard residential solar inverter for low-voltage battery banks (nominally 51.2V LFP or 14s NMC). | Requires Rewiring: The high-voltage EV pack must be dismantled and reconfigured into 14s modules. Safer working voltage, but labor intensive. Examples: Victron MultiPlus, Deye LV. |
| EPS / UPS Mode# | < 20 ms transfer Full inverter capacity |
Emergency Power Supply. In the event of a grid blackout, the inverter disconnects from the grid (islanding) and powers backup circuits from the battery. | Essential for power cut resilience. Keeps heating pumps, lights, medical gear, and internet operating seamlessly. |
| CT Clamp & Meter# | 50A – 100A sensor RS485 / Modbus |
Current Transformer clipped around the main incoming grid live cable to measure real-time household import and export power. | Enables zero-export self-consumption. If the home draws 3 kW, the CT tells the inverter to discharge exactly 3 kW from the battery, zeroing the electricity bill. |
| Battery Emulator# | ESP32 Microcontroller Dual CAN / RS485 |
Translates automotive CAN bus data from the car's BMS into standard inverter protocols (e.g. Pylontech, BYD Battery-Box, SMA). | The core software bridge (pioneered by Dala) that makes used car batteries plug-and-play with off-the-shelf home solar inverters. |
Core electrical parameters, cell arrangements, and longevity concepts explained in plain language.
The formula defining how cells are arranged in series (s) and parallel (p) within a battery pack.
Series (s) connections increase voltage while keeping capacity (Ah) unchanged. Parallel (p) connections increase capacity (Ah) and current capability while voltage remains the same. For example, a 96s1p pack with 3.65V, 120Ah cells delivers 350V nominal and 120Ah (~42 kWh). A 96s2p pack achieves the same 350V using two 60Ah cells in parallel at each step.
The difference between a battery's reference midpoint voltage and its actual working range.
Nominal voltage is the average discharge plateau (e.g. 3.65V per NMC cell, ~350V on a 96s pack). Operating voltage range is the true physical boundary from empty cut-off (~2.8V/cell or 270V) up to full charge limit (~4.2V/cell or 403V). A hybrid inverter must accommodate the pack's entire operating span, not just the nominal rating.
The speed of charging or discharging relative to a battery's total capacity.
A 1C rate discharges an entire pack in 1 hour (e.g. 50 kW on a 50 kWh pack). In electric cars, acceleration can pull 3C–5C (150–250 kW), generating intense heat. In second-life home storage, household loads typically range from 1 kW to 5 kW—which is an ultra-gentle 0.02C to 0.1C load on a car battery. At these low C-rates, cell degradation and thermal strain are almost negligible.
State of Charge is how full the battery is right now; State of Health is how much life it has left.
State of Charge (SoC): The immediate "fuel gauge" percentage (0% empty to 100% full).
State of Health (SoH): The remaining capacity compared to when the pack was brand new from the factory. A 40 kWh Leaf pack with 80% SoH holds 32 kWh when charged to 100% SoC.
The percentage of total battery capacity consumed during a discharge cycle.
Discharging from 100% down to 20% equals 80% DoD. Limiting depth of discharge (for example, operating between 15% and 85% SoC) can easily double or triple the lifetime cycle count of NMC chemistry cells, ensuring a used EV battery lasts 10 to 15+ years in a domestic solar installation.
High-voltage isolation relays and the resistor that prevents destructive capacitor arcing.
Hybrid inverters contain massive input capacitor banks. Connecting a 400V battery directly to empty capacitors creates an instant short-circuit current of hundreds of amps that welds contactor points together. A precharge circuit routes initial current through a power resistor for 200–500 ms until capacitor voltage reaches >95% of battery voltage, after which the main positive contactor snaps shut safely.
Comparison of lithium chemistries found in electric vehicles and home energy storage.
| Chemistry | Nominal Volts | Cycle Life (to 80%) | Thermal Runaway Temp | Common Vehicles & Home Storage Role |
|---|---|---|---|---|
| LFP (LiFePO4)# | 3.2 V / cell (2.5V–3.65V) |
3,000 – 6,000+ cycles | ~270 °C (Very safe, releases no O2) | BYD Blade (Atto 3, Dolphin, Seal), Tesla Model 3/Y RWD. The gold standard for residential solar safety and long cycle life. Flat voltage curve requires ampere-hour counting for SoC. |
| NMC / NCM# | 3.65 – 3.7 V / cell (2.8V–4.2V) |
1,000 – 2,000 cycles | ~210 °C | BMW i3, VW ID series, Renault Zoe, Chevy Bolt, Nissan Leaf 62kWh. High energy density. Sloping voltage curve makes voltage-based SoC tracking very straightforward. |
| NCA# | 3.6 V / cell (2.8V–4.2V) |
1,000 – 1,500 cycles | ~150 °C | Tesla Model S/X, early Model 3 Performance. Very high energy density, but more sensitive to over-temperature and over-voltage. |
| LTO# | 2.3 – 2.4 V / cell (1.5V–2.8V) |
20,000+ cycles | Extremely stable (>300 °C) | Mitsubishi i-MiEV (certain Japanese editions), commercial transit buses. Virtually indestructible, works down to -30 °C, but heavy and bulky per kWh. |
