Portable Power

Lithium batteries have revolutionized the way we interact with the world. Their high energy density and low weight have single-handedly enabled portable electronics and electric vehicles. We no longer need to carry extra batteries, nor do we need to suffer the weight penalty and low performance of lead acid. Power is truly portable thanks to the lithium revolution.

We recently had a couple customers approach us to ask if we can build one-off portable power systems. While such builds are typically a bit more costly due to the fact that they require unique solutions, they really allow us to get our creative juices flowing and come up with innovative ideas that we can use in our mainline products.

You can fit how much in there?

Local First AZ held their annual Fall Fest this past weekend. While we were unable to attend, we did partner with another Tempe-based company, New Use Energy, to build a portable power system for a block party that their Sustainability Program Manager was hosting. We're kicking off a rental program with NUE, so this was the perfect opportunity to showcase big power in a small box.

For this build, we created a 24-volt system that fits inside a box roughly the size of a checked bag. As usual, we used second life batteries that we had analyzed and balanced to ensure maximum life. These were prismatic lithium iron phosphate cells from Elite Power Solutions, another of our local partners. While not as energy dense as cobalt-based lithium batteries, EPS packs can sustain higher drain and have made a name in golf cart power.

We were able to fit 8.3 as-tested kilowatt-hours(!) in the box, with a total weight of about 225 lb. That's 27 lb per kWh; not bad! For reference, a deep-cycle lead-acid battery weighs about twice that. We added a plexiglass cover to show off the batteries without fear of dropping a tool and creating a spark show. We also included a 250a Daly smart BMS with a really cool touch screen, although we sadly didn't take any good photos.

Small but mighty

One of NUE's engineers asked us to pack as much power into a small ammo box as possible. The only direction we had was that it be a 24-volt system with a 100a BMS.

This was a bit more involved, as the layout of the box and especially terminal locations tested our ability to maximize battery fitment. We didn't even have heat shrink that fit, so we elected to stick with kapton tape. It's definitely not water-resistant!

We used Samsung ICR18650-26 cells, which are our favorite 18650s for low-drain applications. Apparently we're not the only ones based the fact that we see more of them than nearly any other single model and they have a very high pass rate for our analysis. We capped it off with a Daly 100a smart BMS with Bluetooth and an inexpensive LCD monitor.

In the end, we were able to fit 3.65 kWh in a 48 lb package. That is not a typo: this 141 amp-hour monster clocks in at a mere 13.35 lb per kWh. That. Is. Incredible.

In conclusion

Lithium batteries have truly brought power into your pocket, and they often last far beyond their first life. This is why we at Higherwire work hard every day to maximize their positive impact and lifecycle. Contact us today to put together a system that meets your needs.