Playing With Laptop Power

About a year ago, a friend sent me an interesting story titled, “People Are Using Old Laptop Batteries to Build Their Own Versions of Tesla’s Powerwall.” Being an engineer and lover of tinkering, I read the article with the zeal of a grad student. Tesla is making DC electricity sexy, but their high price tags (just under $500 per kilowatt-hour) are hard to justify. Apparently other DIYers felt the same, and had been creating their own using recycled laptop cells. I had both the time and thirst for knowledge, so I dove right in.

For the uninitiated, many laptops until recently were powered by batteries built with six or more cells slightly larger than a AA. These cells, 3.7 volts nominal, are combined in parallel to grow their capacity and in series to boost voltage. After some usage, however, one or more cell will fail, effectively rendering the entire battery useless. These batteries are then recycled, and a new one installed. Each of these “bad” batteries, however, still contains at least a few good cells, which can be recharged and reused.

Crack open an older laptop battery -- carefully! -- and this is what you find. Image source.

My search for batteries turned up a number of computer companies near where I lived. Since they didn’t have any use for them, and they were just taking up space in a corner, most were happy to just give me their batteries. A few tried to make a little money off of me, but the cost was still incredibly low. However, I quickly realized that I needed to think bigger. That led me to a recycler of electronic equipment (e-waste), and all the used cells I could handle.

The e-cycler wasn’t free, but I was able to swing a deal whereby I could return any unopened batteries. This is important because modern laptops use prismatic or “pouch” cells (that look like a tea bag). They’re more power dense but also more difficult to handle due to not adhering to a uniform size. I saved a few to use in my boys’ electric scooters, but that’s a story for another time. With piles of batteries* at my disposal, I set off.

My first haul, which probably tested the payload capacity of my Element.

I’ve been working on my suburban off-grid setup for just under a year, and have finally gotten to the point where I can live off of the power I generate.  I’ll be honest: even doing everything myself, the dollar payoff isn’t short-term, but the satisfaction of self-reliance immensely offsets the costs. This blog is dedicated to documenting my decreasing reliance on the electrical companies. Stick with me and I'll show you how I did it.

*I literally purchased nearly a thousand pounds worth of batteries over three separate trips spanning six-plus months, about two-thirds of which were usable.