The Road to Greater EV/Grid Efficiency: Reconfigurable Batteries

Reconfigure it

Don’t connect it with busbars

Efficiency win!

Stellantis IBIS

Last Friday, I was reading John Voelker’s article in Car and Driver magazine, which uncovers that Stellantis has been working for several years on implementing an innovation that increases EV efficiency and range. This despite traction motors achieving mid-90% efficiency, and wide-bandgap-based inverters bettering 98% efficiency these days. But where in an EV system can efficiency increase by 11%, or so, when it seems only 5% or so of headroom is left before getting to 100%?

“[a] Peugeot with the new [IBIS - Intelligent Battery Integrated System] battery design reduced energy consumption by 10 percent—and it cut energy used during AC charging by 10 percent as well, speeding up the charging in the process. A complete home recharge on a 7-kW charging station, for example, was cut to six hours from seven hours.” — Car and Driver magazine

The table below summarizes the benefits of reconfigurable battery technology (RBT).

The grid-storage IBIS system had been in operation since the summer of 2022, the culmination of three years of prior development by a multiorganizational 25-person team. The ability to produce three-phase power, of course, means a three-phase motor can also be powered in an electric vehicle. Hence, the Peugeot test vehicle, which is pictured above.

Porsche Series Unt Parallel

Stellantis isn’t the only OEM looking to reduce cost by eliminating the traction inverter and generating three-phase power directly from the high-voltage battery, which entails reconfiguring the internal battery connections to produce three-phase AC to drive the traction motor of an EV:

“The flexible interconnection of the individual battery modules into a Modular Multilevel Series Parallel Converter (MMSPC) as a distributed real-time system enables dynamic modeling of the voltage curve, so that the sinusoidal three-phase AC voltage for the motor can be generated directly from the DC voltage from the battery modules.” — Porsche, March 2025 Press Release

Daniel Simon, Specialist Project Manager at Porsche Engineering, stated the following in the press release (déjà vu warning):

“With the MMSPC, both the direct control of the electric drive motor while driving and the direct connection to the AC grid for charging the battery is possible”

How It Verks

So, like Stellantis, Porsche is grouping the modules in its battery into three equal arrays of six modules each (some kind of fine German engineering going on that has me scratching my head because it’s non-binary). And it’s synthesizing sine waves with six battery modules of, I’m guessing, around 15s configuration.

The simplest way to explain to my readers how this works is as a six-level voltage DAC, producing six levels of half-wave AC, which can be PWM’d to refine current by exploiting the motor winding inductance. Or maybe they use two modules as roving spares and it’s only a 2-bit, 4-level DAC? Power PAM, lol.

Stellantis, on the other hand, has three equal groupings of eight modules each — a 3-bit voltage DAC and a spare roving module. The roving module means that any of the eight modules can be sidelined for battery balancing; this blog doesn’t have the allowable word length needed to describe everything in more detail.

IP Wars?

So, both Porsche and Stellantis have invested in R&D to increase EV efficiency and lower cost by eliminating the traction inverter and HV battery AC charger as we know it. Stellantis says EVs with RBT may begin production by the end of this decade.

Somebody must be stepping on somebody’s IP toes, or maybe the two companies have a patent cross-licensing agreement in place. Reading between the lines, it seems that the Stellantis team might have thrown down the gauntlet on reconfiguring batteries to produce multi-phase “AC” outputs:

“This [IBIS] system is “the subject of numerous patents and represents a decisive departure from currently common electrical converter systems.” As part of the IBIS project, a number of new concepts were tested and “practical control and operating functions were realised” in preparation for series production in electric cars, but also in stationary energy storage systems.” — Electrive, July 20, 2023.

Though I’m not a patent attorney, my cursory search for Stellantis IP related to a reconfigurable battery discovered the following patent, applied for in August of 2014 and now adjusted to expire in February 2035. The patent, “Dynamic battery system voltage control through mixed dynamic series and parallel cell connections” by inventors Timmons and Okma was assigned to FCA US LLC, now aka Stellantis.

The first, fundamental claim in their patent is as follows:

A lot of patentspeak, but it pretty much condenses down to: Don’t do fixed busbar connections between your HV battery modules like every EV on the planet does. Rather, use switches (as in “transistors” to do it very quickly) so that you can bring each module into a series or parallel combination with its neighbors. This produces a stepped voltage output or stepped higher current output at the expense of voltage. Therefore, you can build a voltage DAC in the vernacular of Electronic Design’s readers.

The Plot Sickens

Like all patents, prior art has to be disclosed to show the patent is novel. One citation in the Stellantis patent in particular comes to mind — a patent application, filed in November of 2010, “Ultra High Efficiency Transmission...for...a Fuel Cell or Battery Powered Electric Vehicle, by the inventor Andy Turudic. Yup...me.

Back in the days after Bob Pease and I “left” National Semiconductor, I decided to go off on my own, on my nickel, and do research on ways to increase the efficiency of electric vehicles. I’ve always had a foot over the line as a gearhead. So, I knew that torque was current and speed was voltage, more or less, and that a “transmission” transmitted the same power out as power in (ignoring losses).

As an electrical engineer, I also knew the basics that the product of voltage and current was power. And if a battery, a combination of cells/modules, was capable of producing a fixed amount of power from its modules, I could arrange the series and parallel combination of those modules to produce either higher or lower voltages, or lower or higher currents.

First gear in a transmission is high torque, low speed — in battery terms, high current and low voltage. So, I could take, say, eight modules, each capable of 1C of current and X voltage, and arrange them to produce 8C of current at X volts, 4C of current at 2X volts, 2C of current at 4X volts, and 1C of current at 8X volts.

Note that connecting these four module reconfigurations to an electric motor means that while each module only outputs 1C of current, the motor can make 8X the torque up to 1/8th of its maximum speed, 4X the torque up to ¼ of its max speed, 2X the torque at ½ of its max speed, and 1X its torque at max speed. We just went through four “gears”... using a battery. By not exceeding 1C, power losses are reduced in the battery modules.

Not only was this applied for by me in a patent, which included generating sine waves in the fashion Porsche and Stellantis just announced they’re doing (confirm by reading the patent — don't rely on this blog), but Electronic Design also wrote a short article on the RBT I had invented.

I also presented a paper on May 18, 2011 in the Detroit area (Auburn Hills) at the CTI Symposium (see figure, Session D5), attended by automotive OEMs including engineers and managers from GM, FCA, Ford, Jaguar, and others. In fact, Jaguar openly conveyed the most interest, with whom I followed up afterwards, but for which they could not get funding. I guess the key to funding is to “have” a patent in the company’s name, not bothering to do a rigorous search for prior art. Otherwise, we wouldn’t have the Peugeot running around with an RBT in it.

Checkmate

So, what happened with my patent application? I decided to give it to the world for free, publishing it EVERYWHERE as prior art so nobody could corner the market on high-efficiency battery reconfiguration technology.

I published the RBT patent application as prior art, Electronic Design described the reconfigurable battery technology in an article as prior art, and I presented the RBT to a who’s who of powertrain engineers in their very backyards in Detroit as prior art. I didn’t abandon the invention; I intentionally gave it to the EV and grid world to go implement.

I’m tickled that the RBT innovation was funded at both companies, and that the grid demonstrator BESS worked as I had predicted. On top of that, cars with the RBT technologies are performing well and delivering 10% reduction in energy consumption as compared to conventional electric vehicles, as I knew it would.

What I’m not happy about is that I gave RBT to the world to use for free as prior art, and now it looks like nobody is willing to share what I believe is my invention. It’s also bittersweet pride to see cars with RBT in them, just as it was with the flat lightbulb I invented that drove LED bulb prices from $50 to less than $10, in that my influence is invisible, despite its significance.

How am I supposed to achieve my life’s goal of being elevated to IEEE Fellow, after a couple of decades as a Senior Member, when nobody gets to see the impact of my work? I made my patent count goal, but that IEEE Fellow nomination has been elusive.

I put the RBT into the public domain for free use by everyone, intentionally. I’m not a patent lawyer, but there’s enough info here in my blog for the rest of the EV and grid storage industry to possibly go ahead and use this RBT tech. That’s if their legal advisors give them the green light, stating FCA’s patent claims may be invalid due to prior art on the fundamental technology published in several places by yours truly.

One more thing... John Voelker’s Car & Driver magazine article on Stellantis’ RBT was published on September 19th — International Pirate Day.

Enjoy the RBT gimme, make the world a better place with it,

-AndyT

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