EV battery packs and home battery packs are not so different. Both typically use a big pile of lithium-ion cells to store energy. In cars, they’re used to get us around, while at home, they’re used to run our appliances and store energy sourced from solar panels. One point of difference is that home packs seldom need to deliver high currents in the same way as automotive packs. Thus, a tired EV battery pack could theoretically serve as a home battery if you so desired. Forget theory, though, because Dala’s already out there doing it.
Dala runs a channel on YouTube called Dala’s EV Repair. He’s explored a number of neat EV topics over the years, from oddball CHAdeMO converters to battery upgrades for older models. But he’s also explored how EVs and their parts can be used in broader ways, with his home battery project being a perfect example of this.
The focus of his project, which took place in 2023, was to see how easily an old EV pack could be hooked up to the grid. This isn’t some big complex build where the individual cells are stripped out and repurposed. Instead, Dala basically just yanked the pack as a whole and hooked it up.
The build starts with a look at Dala’s workshop solar setup. He has a solar installation on the roof capable of delivering 7 kW at peak output. This is paired with a Fronius Gen 24 inverter, which allows the solar panels to be used to power the mains circuits in Dala’s workshop. He then added a battery from a 2017 Nissan Leaf to the system. This allows the battery to store energy generated by the solar panels during the day. In turn, in situations where the solar panels aren’t producing enough energy, such as at night, the battery can make up the difference to keep the workshop powered.
The key to the system is a piece of software of Dala’s own creation. Known as Battery-Emulator, he has made it available on Github. It’s a tool that communicates with the Nissan Leaf battery pack over its standard CAN bus interface. It then translates information from the battery, like state-of-charge and status, into RS485 signals that the Fronius inverter can understand. The software itself runs on a small ESP32 microcontroller board produced by LilyGo. If you’re unfamiliar, a microcontroller is basically a programmable piece of electronics that in this case, is acting as a translator between the Leaf battery and the solar inverter.
Notably, Battery-Emulator isn’t just limited to working with the Leaf battery. It will also work with batteries from the Nissan e-NV200, the Tesla Model S, 3, X, and Y, and the Hyundai Kona, among others. Similarly, it will work with a range of inverters, including products from Fronius, Sungrow, GoodWe, and Solis.
In his video, Dala shows us his proof-of-concept setup, which he had run for 2 months. He simply has the big Leaf pack sitting on the ground, hooked up with a bunch of cables. The high-voltage connections are hooked up to the inverter via a junction box. Meanwhile, the communications wiring from the battery is hooked up to the LilyGo ESP32 board’s CAN bus port. Its RS485 port then sends the relevant data to the Fronius inverter. The ESP32 board runs off 5V sourced from a USB wall charger. The battery also gets a 12-volt feed from a mains adapter to energize its contactor and internal electronics. This is necessary in the absence of the 12-volt lead-acid battery and DC-DC converter that would normally provide this power.
His future plans involve building a proper housing and foundation for the battery, including some fireproofing to protect his workshop if anything should go wrong. Ultimately, though, the simple setup seen in the video shows just how easy it is to use the battery as a home storage solution.
It’s hard to say whether builds like this will become common, as working with EV batteries safely takes a special set of skills. In any case, though, Dala’s work has made it far easier for those experienced in electronics to use old EV batteries with their home solar systems. It’s practically plug-and-play if you know what you’re doing!
Image credits: Nissan, Dala’s EV Repair via YouTube screenshot