What's With the Trailer?

Higherwire repurposed batteries trailer behind a sit-down scooter

You've probably noticed the Higherwire-branded trailer by now (you know, the one that’s featured prominently on our main page) and you might be wondering how that ties into our mission to reduce the barriers to entry for renewable energy storage.

What is it?

We built a towable mobile power station out of a simple bike trailer and basic materials. It includes nearly 7.5kWh of Second Life lithium-ion batteries from one of our partners. We analyzed each battery assembly then wired them in parallel to use as battery backup for our shop scooter.

Features include:

  • 20 USB charging ports capable of 300 watts total
  • 4 110VAC outlets powered by a 500 watt inverter
  • Bluetooth stereo system
  • Integrated solar charger with support for 500w charging
  • LED lighting
  • Inflatable dancer
  • XT90 connector to plug into our shop scooter and extend its range approximately 500%
  • Input port for an AC charger

Why did we build it?

It's a high-visibility and easy way to show off our Second Life process that maximizes the life of lithium batteries. We work with mobility (scooters, e-bikes, EVs) companies to collect batteries that are no longer fit for their initial application, then repurpose them into less-demanding systems. What better way to show off our technology than something that’s fairly easy to bring to events? We debuted it at a the Joshua Tree Music Festival in May and plan to bring it to various Phoenix-area events in the future.

Can I buy one?

We built this to showcase our battery repurposing capabilities, so we have no plans to sell a mobile charge unit like this. Plus something like this would cost several thousand dollars. That said, we do make semi-custom solar generators. See this post for more info.

What are the details?

This idea was born out of a desire to create an easy way to demonstrate our technology. Since most people have lithium-powered personal electronics, what better way to do that than a charging station? Wheels make it even more portable, and the stereo, lights and inflatable dancer attract attention.

We built a simple wood structure onto a regular bicycle trailer. The batteries are 72v nominal (20S), so we needed to buck them down to 12v for a 500-watt inverter, stereo, and LED lighting. We then bucked that down to 5v for the USB chargers. Each of our batteries are fused, and we have a fuse block for each of the loads and charger as well.

This battery was used for testing purposes only.

There aren’t many solar charge controllers for 72v batteries, but we were able to source an inexpensive boost charger from Amazon. It’s not the most efficient system, but it was necessary given our voltage restriction.

We used a pair of Pioneer 6x9” speakers and matched them with an inexpensive Bluetooth speaker. For lighting, we found a Jeep underbody kit consisting of 8 individual pucks. We installed four on the underside and one above the batteries to illuminate our logo via a piece of frosted acrylic. It turned out better than we could have expected!

The front panel (not shown) has an XLR jack to allow us to charge from a scooter charger as well as a main switch to control all loads.

One of the better features of this cart is its ability to connect directly to our scooter, which significantly increases range. Since we’re not always connected and therefore voltages are likely different, we’re using a Fusion Battery Combiner from Electromotive Mods. This ingenious device allows one to run two or more batteries in parallel even if the voltages differ. This means that the scooter runs off of the battery with higher voltage until they equalize, at which point it runs off of both.

We've taken this out around the Phoenix area, and while it gets a little bumpy above 20mph the trailer does surprisingly well overall for its heft (estimated 160lb). We're planning to add larger tires in the future to better accommodate the weight and make it more rugged.

Stop by and get a charge if you see us running around Phoenix.

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