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User:Rgremban/2007 08 01-PriusPlus Project Update

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Click show for a short list of the current PHEV conversion and kit options for the Toyota Prius.

For Prius conversion details see the Prius PHEV article and comparisons table.

  1. Ron's Original PriusPlus History and current Contactor Based PriusPlus documentation for DIY projects.
  2. Ryan's PriusBlue is the testbed for DC-DC PFC Based PiPrius kits and documentation for DIY projects.
  3. Toyota OEM Prius PHEV and Prime Could use some work on this page
  4. Enginer China. But the rest of these appear to all be defunct as of 2020?
  5. |~- Hybrids-Plus USA/Colorado/Li -~|~- EnergyCS USA -~|~- Hymotion USA/Canada -~|~- Amberjac UK. -~|~- EDrive USA -~| Peter mentioned Plug-In Conversions |~-

--={ Project Overview }={ 2007 Maker Faire }={ Theory }={ Instructions }={ Parts List }={ RawData }={ Latest News }=--
--={ Doc Process }={ Mechanical }={ Electrical }={ Electronic }={ Interest }={ Talk:PriusPlus Main Discussion }=--

--={ Historic }={ Battery }={ Schematics }={ PseudoCode }={ Photos }=--

Team Photo from the PriusPlus conversion of Sven's Prius from Nov 2006.

This is the home of the PRIUS+ PHEV DIY (Do-it-Yourself) documentation. These pages are currently anonymously editable, which may change in the future. Please feel free to use the Discussion page for general discussion and commentary on the main article. If you would like to add to an existing section use the "edit" link near that topic's heading. Don't forget to use the Summary field to describe your changes. While editing use the "Show Preview" button to make sure your changes look like you expect them to, before you click "Save Page".

Per EAA-PHEV_Maillist:2007./8./4 or the Yahoo! Archive Regarding the Latest news about the PriusPlus Project Ron Gremban Writes:

It's been a while since we've had a chance to step back and describe the status of this project. Some people have been working incredibly hard to make this happen, while others have been wondering "when will complete plans and kits be available?" The bottom line is that we're getting much closer! A couple of the most adventurous people already have DIY conversions running, and others have started on theirs.

This entire project has essentially been done by volunteers, and we've always been short-handed. Here's a summary and an invitation to get more deeply involved.

One immediate point I’d like to make that bears on the value of this discussion group and why many people may have been wondering if anything has been happening: There have been many private conversations among several parties (me included) pertaining to conversion specifics, control board specifics, etc. I would like to encourage us all to migrate these conversations, except those that really are private between 2 or 3 people, to here. If that ends up overloading this discussion group (as it may, since it also carries general discussions about conversions), we’ll start another group just for technical implementation discussions.


Chris Ewert is one of the first two people to have completed a CalCars/eaa-phev DIY conversion (Kurt Jensen of Nilar is the other; the rest have been done with my supervision). Chris has been working extensively on the do-it-yourself (DIY) documentation, which we believe has now reached the point where an electronics- and mechanics-knowledgeable person can do a conversion with little external hand-holding. To see the current state of documentation, go to <> and click on the various sections at the top:

Theory | Step-By-Step Instructions | Parts List | RawData

If you would like to help with this effort, please email Chris at <>.


PbA: We have a new PbA battery box, designed by Robb Protheroe <>, who will be selling pre-fabricated boxes for a modest price. This steel box with a Lexan cover will solidly mount the 20 EVP20-12s and all electronics except the charger. It hinges and easily lifts using gas shocks for access to the spare tire! The first units should be available around the September time-frame. The PbA modules weigh 280 lb, provide 10-12 miles of EV range, last 200-400 cycles (1-2 years), and cost around $900 from <> (tell Dave at Electric Rider that you are doing a CalCars conversion). We are expecting to document a wiring harness for this conversion, and hopefully fabricate harnesses to be sold at a reasonable price, thereby greatly speeding the conversion process.

NiMH: Robb has designed a similar box for the Nilar NiMH modules <> that are becoming available in limited quantities, and we are working on the add-on BMS board that will be needed with them. 27 or 30 modules (we don't yet know which quantity is best) should provide 20-25 miles EV range, weigh around 230 lb, with an expected cycle life of up to 2000 cycles (6 years of daily use) and an expected cost of $6-7k. (Though our Electro Energy conversion was done first, we do not yet know if modules will become available from them for further conversions.)

Li-ion: Among other possibilities, we are about to begin testing on (2P4S) modules made from 11Ah large-format Li-ion phosphate cells by PSI ( We'll let you know as this progresses. Its potential pricing and range is similar to Nilar's with somewhat lower weight but requiring a more sophisticated BMS (see under chargers, below).


The first turn of the new control board I was working on, not totally unexpectedly, had a few bugs, so we are doing a second version of its layout. We have taken advantage of this to expand its capabilities as follows:

Chris Ewert has designed a microprocessor-based version of the circuits that handle OEM and PHEV battery heating and cooling. This has been moved off the base control board and onto a "Temperature" daughterboard that plugs onto the base "Control Board". The Control Board will be capable of functioning without the Temperature Board (e.g. if needed for debugging), except that battery heaters and fans will not be powered. The new Temperature Board will help optimize PHEV operation in the low- and high-temperature weather that Chris has encountered in Chicago and Jim Philippi has encountered with his Maker-Faire conversion in Texas, but that we had not seen in San Francisco where these conversions were first developed.

  • The Control Board will now accept multiple layers of daughterboards, with force and inhibit signals added and passed between the boards, to handle BMSs for various battery packs -- including Nilar, Electro Energy, and PSI -- as well as future situations we haven't thought of yet. We believe that it will also be applicable to conversions of other Hybrid Synergy Drive vehicles such as Toyota and Nissan hybrids. It may work on the Ford Escape hybrid, too.
  • The driver-visible LED panel has been simplified and (hopefully) made more clear in meaning.
  • To make testing and debugging as easy as possible, a Test Board will be available that will plug into the same sockets as a daughterboard. We will write test procedures to go with it.


  • Chargers are currently our biggest concern. Everything currently available is for PbA and has one or more problems:
  • Delta-q has been amazing at supplying CalCars with prototype PHEV chargers, and its chargers are very nice small, efficient units that are expected to sell for a modest $800 or so. Though production is not slated to begin until early 2008, prototype units may be obtainable. However, the charge control algorithm currently in use (Delta-q chargers can be field-reprogrammed) appears to significantly overcharge the pack. We don't know when this issue will be resolved.
  • ZiVan chargers are also similarly priced. The two issues are that each unit must be custom programmed at the factory to allow a current limit low enough to not blow a 15A 120V circuit, and the power factor is low enough that charge current is more limited than necessary, thereby lengthening charge time.
  • For around $2k, one can also get a Manzanita Micro PFC-40 (40A!) charger. On the downside, it is not line isolated, so more care must be taken to keep the battery pack itself isolated. On the upside, it can double as a DC:DC converter between the PHEV and OEM battery packs, allowing more flexibility in PHEV pack voltage and other advantages (CalCars has not created a design that does that, but this charger is used in that way in the PiPrius conversions <>.
  • I am working on a charge balancing/BMS that will also double as a charger. I plan to make versions available for PbA and Li-ion packs, but maybe not NiMH, due to technical limitations involving NiMH end-of-charge characteristics. Parts costs should be around $500-1000. For a long time I have not had time to work on this, but it appears to be getting more and more critical to the success of conversions.


Several people have begun or are about to begin businesses to sell fabricated components, kits of components, and/or conversion services. You can check the list at Here, however, are a couple of new players not yet on that list and specifically focusing on the CalCars/eaa-phev conversion system:

  • Robb Protheroe <>: pre-fabricated battery boxes and maybe more
  • Kim Adelman <>, conversion services using Nilar NiMH modules, starting with three conversions Aug 15-31.


Last but not least, I'd like to discuss the future of the DIY PHEV project. developed as a collaboration between the Electric Automobile Association <> and CalCars <> to support experimenters in converting hybrid automobiles into PHEVs. CalCars has put its designs and knowledge into the public domain at as a starting point, and I have worked with a small group of very dedicated people to expand this knowledge into a documented, buildable DIY Prius conversion (I sent Chris a thumbnail history of this process that will hopefully be added to the documentation somewhere). This stage is now nearly complete, several conversions have been done, and the status is as I explained above.

We would now like to expand the project into more of a Linux- or gnu-like open source project, with many converters and other knowledgeable people jumping in to provide further documentation (which is already in a wiki, created by Ryan Fulcher), enhancements, kit parts, conversions for other hybrids, etc. To do this without it becoming a free-for-all, we are looking for an open-source Project Manager who can organize and coordinate such an effort, help formulate goals, request and/or accept sub-projects, provide collaborative tools that we may be missing so far, and help ensure some level of accuracy and consistency. Please contact me or Chris if you would like to be considered for that role.

-- +++++++++++++++++++++++++++++++++++++++++

   Ron Gremban,
   California Cars Initiative, a nonprofit organization:
   Moderator & Technical Lead
   PRIUS+ PHEV Conversion Group:
   Do-it-yourself PHEVs: