A Brisbane man spent 18 months collecting and wiring together thousands of discarded batteries to create his own "homebrew" version of a Tesla Powerwall, Elon Musk's home energy storage system, because he "was bored".

Key points: Pete Matthews DIY battery cut his power bill by $1,300

Pete Matthews DIY battery cut his power bill by $1,300 His homemade system uses 4,480 18650-type lithium-ion batteries

His homemade system uses 4,480 18650-type lithium-ion batteries He says 'if you can hold a soldering iron and read a cookbook' you can build one

"[I needed something] to get my ideas out of my skull and onto the bench, so to speak," Pete Matthews told The Link.

The self-taught computer repairman now uses his backyard invention to power his family's off-grid household appliances, excluding his hot water, air conditioning and stove, which are still connected to the grid.

He says his invention can store 40kwh, or 2.8 times the capacity of Tesla's newest 14kwh Powerwall 2.

"My power bill came down from about $1,700 to around $400, so this is significant savings," he said.

Mr Mathews said his system cost him $10,000 and is made from 4,480 18650-type lithium-ion batteries, a generic battery, commonly found inside laptops and other rechargeable consumer devices.

The batteries, which are sold by the kilo by recycling companies, are about 8 cents each, while his other componentry was purchased on eBay.

"You buy stuff off the old interwebs and you solder it up and it actually works," he said.

'A central figure of the DIY powerwall scene'

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The US science and technology website Motherboard recently called Mr Matthews "one of the most central figures of the DIY powerwall scene".

It's a scene where backyard hobbyists around the world share ideas and their experiences scavenging for batteries and designing their home energy storage systems and even cars.

"There's a large emerging community on the DIY powerwall forum and the Facebook group. We're global, everywhere from third world countries to first world countries," he said.

"There's blokes in their sheds, their basements, in their back pergolas, all doing these projects, all having fun, all learning together, all growing as a community. Anybody could do it."

Mr Matthews told The Link he used a licensed electrician to ensure his system was safe and up to code.

He said the projects showed great potential for the energy needs of the third world, where power security is unreliable, recycled parts are available and the need for green energy is greatest.

But Mr Matthews said the bigger global energy picture did not occur to him while building his home project.

"I never once considered the environment," he said.

Mr Matthews is cautious of comparisons to Tesla's product.

"Being realistic, mine's not going to last as long as a Tesla Powerwall," he said.

"I've used recycled cells, they have been overheated, have been overcharged, over discharged.

"[They have had] a hard life by the time I've gotten to them.

"If you can hold a soldering iron and read a cookbook I'm sure you'd be capable of doing this."