Commercial home batteries cost a lot, and this build tackles that head on: a used 40 kWh Nissan Leaf pack, pulled from an electric car, now stores cheap electricity at the maker's parents' house. The idea behind the project is to see whether retired EV packs can stand in for pricey off-the-shelf storage and cut grid bills at the same time.
The work that went into the mounting alone is worth a look. Battery Man welded a tubular steel frame, painted it black, and fixed it to the exterior brick wall using threaded steel rods set in chemical resin. A folding hydraulic engine hoist then placed the pack upright against the wall. On the electronics side, a Stark Box handles the translation between the Leaf's battery management system and the existing 10 kW Fox ESS hybrid inverter, holding a Stark CMR control board, an ESP32-based Battery-Emulator, a 12V DC supply and a CHNT breaker, plus a BENY DC isolator with fuses. The high-voltage wiring reuses a modified Renault Zoe harness, crimped with a hydraulic tool.
Configuration happened over the Stark CMR's Wi-Fi hotspot, picking the Leaf profile and setting CAN communications and GPIO pre-charge values. An early contactor error was cleared by adjusting those pre-charge and closure settings, and after that the inverter showed live battery data. Discharge into the house was confirmed on the Fox ESS app at roughly 650 to 680 W.
Everything sits inside custom wooden cladding with ventilation gaps top and bottom, meant to blend into the garden and keep weather off. One open question remains: how many years a road-retired pack can realistically keep serving a home.
Project by Battery Man. Watch it on their YouTube channel: