Toyota Repurposes Hybrid Batteries for Off-Grid Battery Storage System

While it might not be a fan of battery electric vehicles, Japanese automaker Toyota has a lot of experience with the long-life nickel-metal hydride battery packs used in the majority of its hybrid vehicles since the launch of the original Toyota Prius sedan back in 1997.

Life after the hybrid: Toyota hybrid battery packs can easily be modified to work in a backup power system.

Life after the hybrid: Toyota hybrid battery packs can easily be modified to work in a backup power system.

Smaller in capacity than the battery packs used in modern electric vehicles, these NiMh battery packs can last more than 100,000 miles in their original car, offering limited electric-only operation for low-speed maneuvering and city-centre travel. But as the cars these batteries are in cease to need them — either due to battery replacement or upon vehicular recycling at the end of the car’s life — the battery packs themselves can still serve a useful life as backup batteries for grid-connected and off-site backup systems.

To demonstrate that fact, Toyota [NYSE:TM] — working with the Yellowstone National Park — has just turned on a brand-new off-grid 85-kilowatt-hour energy storage system built entirely with repurposed Toyota Camry Hybrid battery packs at the Lamar Buffalo Ranch. Combined with a brand-new 40 kilowatt peak photovoltaic solar array, the 208 repurposed hybrid battery packs provide all-day, renewable power at the remote facility for the first time in its history.

In this case, all 208 used NiMH batteries came from used Toyota Camry Hybrids.

In this case, all 208 used NiMH batteries came from used Toyota Camry Hybrids.

Of course, the idea of repurposing electric car and hybrid car battery packs for off-grid and grid-tied energy storage projects isn’t exactly new. Here at Transport Evolved, we’ve shared numerous stories covering second-life projects for electric vehicle battery packs. But what strikes us about Toyota’s project in Yellowstone is the simplicity of the system.

Instead of repackaging the cells of each battery pack into a new battery array, Toyota’s engineer —  working with Indy Power Systems and Yellowstone National Park — have designed an storage rack system that allows the used hybrid packs — internally rewired to change the cell connections from series to parallel —  to simply be slotted into position in their original cases, plugging each into a built-in wiring loom that arranges the battery packs in four arrays of 52 battery packs each.

The parallel-series arrangement is then connected to an Indy Power Systems energy management and power inverter system, which manages the flow of energy into the battery packs from the solar array during the day, and helps provide 110-volts AC out when needed.

While some work is required to rewire the internals for each battery pack — disconnecting the original busbars that formed the series cell connections, switching around every other cell and then attaching a long parallel busbar, there’s still some benefit to using the original battery cases.

Firstly, it means that the NiMH cells have appropriate compression and mechanical lockdowns without building new compression strapping for each battery pack.

Second, it means that each battery pack can be individually replaced in the case of a failure, with replacement simply a matter of removing the defective pack and replacing it with a new one.

Reconfigured individual packs are slotted into the racking.

Reconfigured individual packs are slotted into the racking.

Thirdly — and most importantly perhaps for the remote location — each battery pack can be lifted by hand, negating the need for expensive lifting equipment usually needed for servicing large grid-tied and off-grid battery systems.

As Tesla Motors [NASDAQ:TSLA] recently-announced Tesla Energy products demonstrate, battery packs for both domestic and commercial use to help smooth out grid demand and even allow communities to function off-grid are in high demand. In the case of Tesla, those battery packs are brand-new, manufactured by Tesla exclusively for the purpose of static energy storage.

But for those who like upcycling and recycling, this particular project demonstrates what some careful planning can lead to, without wasting any mechanical or electrical components.


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