Ford Files Patent for a Roof-Carried Spare EV Battery

Ford recently filed a patent for an backup battery pack that EV owners can bring along so they don’t have to worry so much about range. The battery, shown housed on the roof of the car, contains battery modules, a backup battery assembly, and a connection port to maximize ease. The patent images use a Ford Bronco as the demo car. Could an electric Bronco be closer than we think? Either way, this invention is probably not coming soon.

There are two things we know to be true about the EV market: Automakers want to promote the adoption of electric vehicles, and consumers are worried about range. Now, as first reported by Electrek, Ford has applied for an innovative patent for a backup battery pack that can travel on the roof of the vehicle. This patent looks like a novel way to address the range anxiety and charging concerns that people often associate with EVs, especially on extended trips. One suggestion in the patent application is that these battery packs could be “rented or leased prior to an off-roading trip, for example.”

The patent outlines a mechanism designed to provide additional power and range to EVs when the primary battery is depleted. It’s a modular system that’s intended to be compatible across different EV models and, at least according to the description, simple to maintain and upgrade. The units are stacked to provide the most capacity.

U.S. Patent and Trademark Office

Beyond the fact that a roof-mounted battery pack is sitting on top of the vehicle in these drawings, it’s interesting that the vehicle used resembles the Ford Bronco. We wonder if this is a hint that an EV version of Ford’s big-selling Bronco is coming soon.

So Many Questions

But we, like others, have questions, principally: How does Ford plan on reinforcing the roof to handle the weight? A rack can’t do it alone. And how does the battery get up there (and down again)? EV battery packs’ weight can range into the thousands of pounds.

The patent application explains that the battery is removable, which leads us to believe this roof-mounted pack won’t have the capacity of the large packs automakers use to power their EVs. This ought to ensure the pack weighs just a couple hundred pounds—a sum most roof racks are capable of holding. For instance, the original Prius plug-in hybrid’s 4.4-kWh battery hit the scales at a manufacturer-claimed 176 pounds.

Michael Simari|Car and Driver

That doesn’t mean it’ll be easy to hoist a battery pack on your EV or PHEV’s roof. Anyone who’s ever used a roof-mounted cargo carrier can tell you that you’d likely need at least one other person to assist with this task.

Assuming our hunch is correct, then we think the potential product this patent hints at will serve the equivalent purpose of a gas car’s reserve tank. That said, given the extra weight and negative effects on aerodynamics the additional pack will have on an EV, it’s possible this concept actually worsens an EV’s range, particularly at highway speed.

At lower speeds, though, such as in off-road environments, this roof-mounted battery pack may just offer the little bit of extra juice needed to get back to the trailhead. Adding a set of solar panels could make this concept even better, as they’d allow the roof-mounted pack to—slowly—replenish itself, too.

It seems evident that this invention is not going to become a reality anytime in the near future. It must be a placeholder for a future time when Ford has the right electric off-road vehicle to use it with—and, more important, when battery technology has advanced sufficiently that the weight is not an issue anymore.

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Despite their shared last name, Greg Fink is not related to Ed “Big Daddy” Roth’s infamous Rat Fink. Both Finks, however, are known for their love of cars, car culture, and—strangely—monogrammed one-piece bathing suits. Greg’s career in the media industry goes back more than a decade. His previous experience includes stints as an editor at publications such as U.S. News & World Report, The Huffington Post, Motor1.com, and MotorTrend.