Salvaged Leaf pack runs an off-grid workshop through a Fronius inverter

PrairieCarl71 1 day ago

A workshop that needs to run off-grid for eight months a year is a serious load for any storage setup, and buying a purpose-built battery at that scale gets expensive fast. The maker behind Dala's EV Repair took a different route: a salvaged 2017 30 kWh Nissan Leaf high-voltage pack now feeds a residential solar system, backed by a 7 kWp rooftop array and an ABB vehicle charger.

The wiring side is done properly. A 50 mm² orange cable carries the high-voltage connection from the battery into a junction box, where it steps down to 10 mm² cables feeding DC disconnect switches and a Fronius Symo GEN24 Plus inverter. The clever part is the control layer: a LilyGO ESP32 CAN/Modbus transceiver board in a gray enclosure converts battery CAN messages into Modbus registers the Fronius recognizes. An OBD-II port spliced into the harness lets LeafSpy watch cell metrics. The wall-mounted distribution box runs from a 230V-to-12V wall adapter, and its breakers, labeled A through D, act as manual switches that sequentially trigger precharge, the negative and positive contactors, and the internal BMS.

What stands out to me is that all the safety features of the Leaf battery are retained, and the whole project is documented with open-source schematics on GitHub. The Battery-Emulator project there explains connecting a LEAF battery to a BYD compatible inverter.

It is not finished, though. Permanent fireproof mounting is still on the list, as is a low-voltage backup for the 5V microcontroller. Chademo support is in development with testing ongoing, and expanding software compatibility to Tesla battery modules is a future refinement.

Project by Dala's EV Repair. Watch it on their YouTube channel:

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SummitDad_1969 1 day ago

This is a really clean integration. I am curious about the startup sequence: with breakers A through D acting as manual switches, does the maker have to run through precharge and the contactors by hand every time, or is there some way it powers up automatically when the sun comes up? Also, does the ESP32 board need to be alive before the inverter will talk to the pack?

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FlintHand 1 day ago

From what the maker has shared, the labeled breakers sequentially trigger precharge, the negative contactor, the positive contactor, and the internal BMS, so that order is built into the switching sequence. On the power question, the distribution box is fed by a 230V-to-12V wall adapter, but whether that gives automatic startup or needs manual switching has not been said. The low-voltage backup for the 5V microcontroller is only planned, so how that affects startup is still an open point.

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