The Fathers of Fast Charging: The Story of the First 250 kW 10-Minute Fast Charge

Charles Botsford, P.E., Monrovia, California

The Fast Charge Event

On May 17, 2007, AeroVironment, Inc (AV) engineers instant charged a 35 kWh electrical automobile battery pack in 10 mins [1]. Witnessing the tournament have been Tony Andreoni and Craig Childers of the California Air Resources Board (ARB).

The pack, comprising Altairnano modules designed for Phoenix Motorcars’ electrical sports activities software truck, started at 0 p.c state of price and ended at roughly ninety-five p.c state of price.

35kWh Lithium Titanate Battery Pack

Figure 1. 35kWh Lithium Titanate Battery Pack

The Battery Technology

Altainano used a lithium titanate battery chemistry for his or her packs. The benefits of lithium titanate chemistry over different lithium chemistries are:

  • Long cycle existence – on the order of 5,000 complete 100 p.c intensity of discharge (DoD) cycles
  • Long calendar existence – 20 years?
  • True 10-minute instant price price – this interprets to a 6c price price. 1c price price is a complete battery price in 60 mins. 6c is six instances that price or a complete price in 10 mins.
  • Highly protected – very low attainable of thermal runaway when put next with different lithium chemistries

The disadvantages of lithium titanate chemistry are:

  • Low explicit power – in the vary of 60-80 kg/kWh, which interprets to 50 p.c heavier packs
  • High value – roughly 20-30 p.c costlier than different lithium based totally chemistries. The low explicit power interprets to extra lithium required in keeping with kWh.

Thirteen years later (i.e., 2020), the excessive value and coffee explicit power disadvantages have confirmed tricky to conquer relative to the gentle responsibility EV marketplace. However, lithium titanate remains to be aggressive for the heavy-duty automobile marketplace, particularly transit buses.

This point of view is essential in figuring out why automobile builders have been excited about lithium titanate in the 2007 time period. A battery pack that wouldn’t degrade, had decrease thermal runaway chance, and ultimate eternally would remedy maximum of the issues an automobile producer confronted as they advanced a brand new EV style. The talent to instant price in lower than 10 mins used to be now not handiest icing on the cake, however intended a compelling method to deal with “range anxiety.”

At the time, Altairnano used to be the first corporate growing lithium titanate. Later on, Toshiba, with its SCiB era, labored with a number of massive automobile producers, together with Honda (the Fit) and Mitsubishi (i-MiEV) to commercialize the era.

Proving the Battery Technology

By the early 2000s, AeroVironment (AV) had greater than 20 years of battery checking out and pack construction revel in, beginning with the construction of the GM Sunraycer and GM Impact in the overdue 1980s and early 1990s. That revel in integrated in depth paintings with lead-acid, nickel steel hydride, myriad lithium chemistries, and plenty of sorts of gasoline mobile applied sciences.

AV have been at the leading edge of instant charging of EVs – beginning with EV1, then the instant charging of battery electrical forklifts. For electrical automobiles, those efforts met with restricted luck since no battery chemistry used to be succesful of accepting a quick price at sensible charges. This modified with the construction of the lithium titanate oxide (LTO) batteries – and their sensible implementation via Altairnano. AV known early that the instant charging features of this battery chemistry merited consideration.

To say that AV engineers have been skeptical of new battery claims is an irony. Battery builders steadily commissioned AV to check and validate their new and newest batteries. Often, the claims have been really fantastic, and simply as continuously proved fallacious. One AeroVironment engineering supervisor had a announcing, “There are liars, damn liars, and battery suppliers.”

When Altairnano got here to AV with the claims indexed above, the engineers have been extremely skeptical to mention the least.

Testing started at the mobile point. Cell checking out is slightly reasonably priced and temporarily determines whether or not additional checking out at the module or pack point is warranted. It used to be. Much to the amazement of AV engineers, mobile checking out handed 6c price and discharge checking out from 0 to 100 p.c state-of-charge (SOC). After roughly 1000 complete DoD cycles, no degradation used to be detected. Testing additionally integrated time in a thermal chamber and witnessing of nail penetration and different damaging checking out to ensure that the mobile meets the protection requirements already established.

One unexpected word used to be the capacity of the mobile to discharge to 0 SOC, which is one thing extremely discouraged universally via lithium battery producers.

Next used to be the module point, the place efficiency issues continuously crop up. A module contains many cells and calls for a battery control machine for mobile balancing, thermal tracking, voltage regulate, and different control parameters. Due to the very low inner impedance of lithium titanate, the battery control machine had no bother with mobile balancing and controlling the module. AV engineers spent a lot more effort and time with module checking out as a result of checking out at the pack point is much more crucial. The pack-level battery control machine controls more than one modules—28 modules for the Altairnano pack.

The Pre-Test and Test

On the night of May 16th, 2007, AV engineers carried out the first pack-level pre-test of the Altairnano pack the use of an AV-900 complex battery cycler, which is rated at 250 kW. The goal used to be to test all programs, particularly protection. Pushing that a lot persistent into an EV pack had by no means been executed earlier than. The pack used to be discharged to 0 p.c SOC that night time.

On May 17th, 2007, with everybody status again and protection goggles in position, the AV-900 battery cycler started charging the pack.

The absolutely charged 35 kWh pack, in ten mins, theoretically calls for 210kW (35 x 6C = 210 kW). However, machine losses from pack inner resistance, cabling, contactors, and battery control machine, greater the exact persistent required from 215 to 240kW, pushing the AV-900 to its limits.

The charging proceeded as anticipated. AV engineers adopted the expanding pack voltage, which indicated the pack used to be charging in line with the SOC/voltage curve.

At simply lower than ten mins into the check, one of the ARB representatives spotted {that a} cable connecter at a pack contactor used to be smoking. The check used to be in an instant close down. The pack used to be charged to roughly 95 p.c SOC.

Over the subsequent a number of months, battery checking out at the module point showed the claimed attributes of the lithium titanate chemistry.

Test Implications

Demonstrating {that a} battery may well be safely and completely charged in ten mins used to be a big accomplishment for the EV trade. The Society of Automotive Engineers (SAE) J1772 DC charging subcommittee in an instant started comparing connector era for the 250kW persistent point and initiated construction of a brand new instant price same old.

supply: Botsford [2]

Figure 2. High Power DC Vehicle-Side Connector – early ideas

However, that effort used to be by no means finished, basically because of fears via automobile producers that batteries may just now not be fast-charged. Many years later (~2012), SAE followed a 50kW mixed charger machine (CCS) same old, which might compete with the 50kW CHAdeMO (Japanese) same old already in position. Several years after that, SAE greater the persistent prohibit of CCS to roughly 400kW and a most price present of 500 A.

The Heavy-Duty Market – A 500kW Transit Bus Charger

By 2010, Proterra, a transit bus producer, had effectively advanced an electrical bus succesful of  high-power charging the use of the Altairnano lithium titanate batteries. The first Proterra instant price electrical buses have been put into earnings carrier at the Foothill Transit Agency (Southern California). AeroVironment advanced the first 500kW charger, which comprised 4 125kW persistent modules. A video of the charging machine may also be discovered at:

The Fathers of Fast Charge

Phoenix Motorcars, Altairnano, and AeroVironment collaborated in growing and demonstrating the instant price chemistry and era. Those concerned come with:

Phoenix Motorcars

Rick Reinhard – Project engineer


Evan House, PhD – Battery specialist

Alan Gotcher – CEO

Bob Goebel – Business Development

AeroVironment, Inc.

Omo Velev – Project supervisor

Ron Norton – Standards engineer (Ron had a harness round his neck right through the check, able to drag the pack out of the excessive bay in case one thing went extraordinarily fallacious. This article is written in his reminiscence.)

Adam Szczepanek – Lead engineer and topology fashion designer of the 500kW instant charger

Bill Norris – Battery control specialist

Mike Vail – Power electronics engineer

Al Flack – Power electronics engineer

Scott Berman – Power electronics and instrument design engineer


Many tasks have been carried out and merchandise advanced in the 1990s on the instant price of batteries of every kind: lead acid, nickel steel hydride, and lithium chemistries. By the early 2000s, “extreme” 10-minute instant charging emerged as the holy grail. Meanwhile, one-hour instant charging used to be in the works for the a few years of requirements construction that lie forward.

The 2007 demonstration of true 10-minute instant charging at the pack point, with a real EV battery pack, confirmed the requirements builders they must set the limits to excessive persistent ranges, 250kW and past. A decade later that’s what started to occur with each the mixed charger machine (CCS) and CHAdeMO requirements.


1. Botsford, C., Testimony earlier than California Air Resources Board on May 24, 2007.

2. Botsford, C, A. Szczepanek, “Fast Charging vs. Slow Charging: Pros and Cons for the New Age of Electric Vehicles”, EVS24, Paper No. 3960315, Stavanger, Norway, May 2009.


Charles Botsford, PE is a certified chemical engineer in the State of California with 30 years’ revel in in engineering procedure design, dispensed era, EV charging infrastructure, and environmental control. He has participated in California’s Vehicle Grid Integration (VGI) Working Group and participates in the Society of Automotive Engineers (SAE) J3072 AC Vehicle-to-Grid requirements committee. Mr. Botsford holds a bachelor’s stage in chemical engineering from the University of New Mexico, and a grasp’s stage in chemical engineering from the University of Arizona.