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PRIUS+ Fact Sheet: version 1.4 (16K text message, PDF available)
Apr 4, 2005 (From the CalCars-News archive)
This posting originally appeared at CalCars-News, our newsletter of breaking CalCars and plug-in hybrid news. View the original posting here.
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Below is the latest version in text format. It's also available as a neat 3-page 50K PDF document from links at

No new sections in this document, but many important clarifications, improvements and elimination of embarrassing typos.

  • Emphasis early on that you can't talk about 120-180 MPG (or 500 MPG) without talking about the electricity used.
  • Specific reference to the frequently raised Q about the relative emissions of EVs powered from a dirty (coal) grid vs. gasoline.
  • Links to the websites of vendors and partners.
  • Significantly changed sections about CalCars, making the document suitable to pass along to potential supporters of the effort.

FACT SHEET: CalCars PRIUS+ Prototypes version 1.4 April 3, 2005

1. Specifications
2. Performance data of current prototype
3. Future prototypes and consumer conversions
4. Preliminary performance data of partnering groups' conversions
5. How and when can I get a PRIUS+?
6. About CalCars (sponsor of PRIUS+ Project)

This summary of two conversions completed since fall 2004 brings you up to speed on what we've done -- and where we're heading. This Fact Sheet is a work in progress (check at to make sure you're reading the latest version, and, if you're reading the email version, pick up a neatly formatted (currently 3-page version). For the latest technical discussions, see the Conversion Group URL below. Subscribe to the Newsletter to keep up with the latest news coverage and milestones. Note that all our mpg reports also include electricity use no free lunch! Contact us if you're interested in becoming involved!

-Felix Kramer fkramer@... -- Founder, California Cars Initiative
-Ron Gremban rgremban@... -- Technical Lead, PRIUS+ Project and Info­group/­calcars-news CalCars-PHEV Newsletter­group/­priusplus/­ PRIUS+ PHEV Conversion Group


  • Conversion platform is Ron Gremban's stock 2004 Prius hybrid (HEV).
  • Prius hybrid battery pack (Panasonic nickel-metal hydride (NiMH) 6.5 Ah, 201.6 Volt, 99 lb/45kg.) remains unused during PHEV operation and can be used in normal hybrid mode as needed, e.g., for comparison (in future prototypes, this battery may be removed).
  • CalCars' inital battery pack, completely replacing Prius pack (for this temporary first prototype, we used low-performance but resilient lead acid (PbA) for testing purposes and to obtain design criteria for higher-performance packs): 18 electric bicycle B&B 20Ah 12Volt SLA batteries from (nominal 12 Ah, 2.4 kWh total at the car's high discharge rates, 216 Volt, 240 lb without associated hardware and components).
  • Batteries positioned in empty well below hatchback deck, with independent manually switchable air cooling system.
  • Batteries recharged via standard 110-volt outlet in 3 hours with Brusa NLG5 charger from (cheaper charger, longer time for larger packs).
  • Battery Management System and Controller/Display Unit (CDU) by Energy Control Systems Engineering ( of Monrovia, CA, replaces Toyota's Battery ECU. No change to the rest of Toyota's Hybrid Synergy Drive (HSD) -- what used to be called Toyota Hybrid System (THS).
  • Data from battery and CAN (Controller Area Network) bus interface. Dashboard analog meters display battery voltage and current. EnergyCS in-dash digital display includes battery voltage and current, Amp-hours used from the battery, vehicle power requested (e.g. via throttle position), battery state-of-charge (SOC) reported to the THS, and thousandths of gallons of gasoline used per trip.
  • State of Charge information sent to THS is set semi-automatically to force energy use and regenerative braking regimen (automation will be fine-tuned in future iterations).
  • Configuration permits rapid reversion to standard hybrid operation using the Prius's Battery Management System and retained original battery.
  • Operation permits electric-only mode at up to 34 mph; above 34 mph, battery energy continues to assist the engine, contributing to lower gasoline consumption. The PbA battery is good for 10 all-electric miles, 20 assisted miles, or mixes of the two. Then operation reverts to normal HEV mode, still using the new battery pack.


  • Heavy lead-acid batteries add approx. 300 lb (10%) total, reducing mileage by approx. 5 mpg (10%) in standard HEV operation on city streets (because of acceleration losses), but by little or nothing at highway speeds (where wind resistance is the main factor). Lower internal resistance of future (lighter) battery packs is expected to increase the efficiency of standard HEV operation sufficiently to restore original standard HEV city mileage even when grid-charging energy is not involved. Equivalent mpg numbers and operation costs depend on patterns of use (total miles driven/day, speeds driven). The following examples show improved performance (expected to be better with lighter, more efficient batteries. IMPORTANT: low PHEV and HEV mileage is due to short runs, hilly Marin County terrain, and other local factors.
  • Under 10-mile all-electric propulsion (at under 35 mph), infinite mpg (i.e., no gasoline use) plus 262 grid Watt-hours/mile vs. 50-60 mpg as a normal HEV.
  • 14 mile round trips, including approx. 10 miles on hilly freeways: 58-105 mpg + 185-226 grid Wh/mi, compared to 34-38 actual HEV mpg on the same course, driving with the extra battery weight -- otherwise maybe 37-41 mpg.
  • 26-28 mile trips with many surface streets: 55-65 mpg +124-164 grid Wh/mi.
  • Beyond 20 miles/day (40 miles/day with NiMH or 50+ miles/day with Li-Ion batteries), normal HEV mileage -- except better mileage on long descents due to ability to store more recovered energy -- and no further electricity use. All-electric miles: power cost, approx. 1.25 cents/mile (assumption of 250 Wh/mi and 5 cents/kWh on California off-peak EV "E-9" (PG&E) rate, and not amortizing battery cost), vs. approx. 4.5 cents/gasoline mile ($2/gallon, 45 mpg). Charging with otherwise unused/unsold photovoltaic power costs zero/mile (not amortizing system cost).


  • Nickel-metal hydride (NiMH) (27Ah, 5.4 kWh, 225 lb extra after removal of existing battery); up to 20 mile all-electric range or 40 mile assisted range.
  • Lithium-ion (Li-Ion) (35-40 Ah, 9 kWh, 160-190 lb extra after removal of existing hybrid battery); up to 30 mile all-electric range or 60 mile assisted range. (See also Section 4 below for EnergyCS Prototype) Improved performance as well as additional electric range can be expected from the above batteries, due to significantly lower internal resistance losses.
  • Then, we hope, "installed kits" for purchase from third-party partners!
  • For the latest details (between updates of this Fact Sheet) see the CalCars Vehicles page and subscribe to our Calcars Newsletter (see section 5 below).


EnergyCS's version of PRIUS+, completed Feb. 2005, uses $15K of off-the-shelf Valence Technology Saphion U Li-Ion batteries (for pack spec see Section 3 above), plus specialized monitoring and control circuits. These encourage EV operation at low speeds and during low power usage and provide electric motor benefits at all speeds. Equivalent mpg numbers and operation costs depend on patterns of use (total miles driven/day, speeds driven). Following are initial examples from late Feb.-early March 2005: (Later this year, EnergyCS will document performance in partnership under recognized external testing auspices..)

  • Under 35-mile trip all-electric propulsion (at under 35 mph), infinite mpg (i.e., no gasoline) plus 200 Watt-hours/mile.
  • 70 mile trip, 80% 55 mph freeway, 20% city: 120-180 mpg + 115-150 grid Wh/mi, compared to est. 55 mpg as a normal HEV.
  • Beyond 50-60 miles/day, normal HEV mileage -- except better mileage on long descents due to ability to store more recovered energy -- and no further electricity use. All-electric miles: power cost approx. 1.0 cents/mile (assumption of 200 Wh/mi and 5 cents/kWh on California off-peak EV "E-9" (PG&E) rate, and not amortizing battery cost), vs. approx. 4.5 cents/gasoline mile ($2/gallon, 45 mpg). Charging with otherwise unused/unsold photovoltaic power costs zero/mile (not amortizing system cost).


Thanks for asking. We've started a list to keep people up-to-date on the progress of PRIUS+, CalCars, "gas-optional hybrids" (GO-HEVs) or "plug-in hybrids" (PHEVs) in general. At­group/­calcars-news, subscribe to the low-traffic CalCars-PHEV Newsletter, and watch our website for our progress.

These vehicles will operate like any other Prius, with no necessity to drive slower or differently. They will re-charge overnight from conventional 110-volt outlets (no need to hunt for a place to plug in during the day).

Though we do not yet have any information about when conversion options will be available to individuals or what they will cost, when they do (from for-profit companies, not directly from us), we expect they will be installed kits. They will include a warranty for the components, but Toyota could decide that the conversion voids some or part of your car or hybrid system warranty (unless the company worries that will tarnish its green image). We won't know how dealers will respond to service requests for this car until we start driving them.

We expect to be able to convert 2004-2006 Prius (not early generations). We think conversions will be possible for Toyota Highhlander and Lexus RX-400 hybrids, and probably for Ford Escape. Because of their different architecture, we are not investigating the feasibility of converting Honda Insight, Civic or Accord hybrids.

To learn more about PHEVs, hybrids and alternative fuel vehicles:­group/­priusplus/­ - PRIUS+ PHEV Conversion Group discussions­group/­gridable-hybrids -- PHEV general discussions­group/­Prius-2G -- 2004 Prius issues­group/­Prius_Technical_Stuff -- Prius nuts and bolts -- general Prius info and talk -- all about hybrids -- general discussions of alternative fuel and advanced technology vehicles

Meanwhile, we thank you in advance for your encouragement, and hope you'll spread the word about our efforts. If you know of any individuals in a position to discuss fleet purchases, provide us with substantial support or celebrity endorsements, please send them our way. If you want to contact Toyota to tell them you'd like a Prius or other Toyota/Lexus/Scion GO-HEV, we suggest you contact your local dealer, and feel free to send a copy of any email you write to priusplus@....


The California Cars Initiative ( is a Palo Alto-based nonprofit startup. We're a group of entrepreneurs, engineers and other citizens promoting high-efficiency, low-emission cars and harnessing buyer demand to help commercialize advanced technologies. Somewhat uniquely, we focus both on public policy and technology development.

We're demonstrating the immediate opportunity and benefits of what are - called "gas-optional" or "plug-in" hybrids (GO-HEVs or PHEVs). The next generation of hybrid cars can be based entirely on existing components. They're basically like some current hybrids but with larger batteries and the ability to re-charge conveniently, so local travel is electric, yet the vehicle has unlimited range. While hybrids may trim gasoline use by a third, PHEVS can cut another third or more. It's the future pathway to multi-fuel PHEVs, including bio-diesel. And PHEVs makes hydrogen cars more affordable and efficient by reducing the size of the fuel cell stack and the amount of hydrogen stored and used. PHEVs make sense in states like California, where the power grid is relatively clean, but even when powered by the "dirty" (50% coal) national grid, produce far lower emissions than gasoline cars (and use domestic fuels.)

We call our prototype conversion "PRIUS+." It's a stock 2004 Prius to which we've added batteries and grid-charging, - to showcase plug-in hybrids and encourage car makers to build them. (We've replaced the battery control system but haven't tinkered with Toyota's Hybrid Synergy Drive.) Our proof-of-concept uses lead-acid, which we'll soon replace with nickel-metal batteries,: our Southern California partners have an advanced lithium version of PRIUS+.)

We hope to persuade Toyota and other automakers to build PHEVs for a market we expect to expand as the Kyoto Protocols and parallel state and international greenhouse gas initiatives are phased in -- and as oil prices remain unstable or rising. We're demonstrating demand initially from early adopter individuals and institutions. We're working closely with other PHEV advocates to develop fleet orders from utilities, government and private companies. With our for-profit integration partners, we hope later this year to offer installed conversion "kits" to celebrities and entrepreneurs. We're looking first at cars that use Toyota's Hybrid Synergy Drive (Prius, Lexus, Highlander, Nissan), followed by Ford's Escape and other forthcoming full hybrids.

We're also involved in advocacy and public policy, bringing together the growing attention given to this "up-and-coming" technology (see our roundup at­kudos.html). We're educating the large market of car buyers who will pay extra for better cars. We're presenting the benefits of PHEVs, along with wind and solar power, as a coordinated response to two of today's greatest challenges: global warming and energy security. We're exploring with public officials ways to provide incentives to auto makers to build PHEVs, and with government and industry suppliers the opportunities to create a new entity to design, produce and assemble PHEVs in California in partnership with an automaker.

We're a mostly-volunteer effort, that's gotten contributions from a well-known entrepreneur and a major foundation, with others to come. We document our effort at our open-source-style technology discussion group at­group/­priusplus/­.

And here's the (non-profit) advertisement: we ask that you support us by becoming a Charter Sponsor (tax-deductible contribution of $95 or any other amount at­sponsor.html -- we are an almost-entirely volunteer operation, and could do much more with additional resources!

California Cars Initiative info@...
PO Box 6122 Palo Alto, CA 94306

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