I converted this xB to full electric drive.

Scion xB EV

This section of my new site is mostly done at this point,  but I will likely still be refining and adding information over time.

This is the main page for my 2004 Scion xB EV (electric vehicle) conversion.   The Scion replaces my old 1985 Toyota MR2 EV conversion, which I completed in 2007 and drove for 6 years as my primary around-town car until the scion came online in June 2013.

For EV Conversion concepts and terminology, look at the EV Terminology.

For some idea of the research I went through to select a chassis and design it to meet my goals, refer to Research and Analysis.

For nauseating detail on the build, jump straight to the Construction page.



  • Solectria AC55 motor with UMOC445F Inverter
  • 320V, 100AH, 32kwh lithium battery using 100 GBS lithium manganese prismatic cells.
  • Manzanita Micro PFC-30 charger
  • J1772 inlet and adapter module allows use of L2 public charging stations.
  • Elithion Pro BMS
  • 4.8:1 overall ratio direct drive via synchronous belt system and 1984 Toyota celica GTS differential and custom CV shafts.
  • 1.5kw electric heater


  • 3040lbs curb weight
  • 100hp with 175ft-lb motor torque from 0-3000rpm;
  • Regenerative braking
  • 80mph design top speed
  • 4800 motor RPM at 60mph.
  • 0-60 15s (estimate)
  • 250wh/mile battery to wheels under most driving conditions; 100 mile useful range.


While my 1985 Toyota MR2 EV was very successful, my wants and needs in a car have been changing.  In addition I now have a bit more budget available than I did when I built the MR2.   I wanted a car that would:

  • Seat 4
  • Tow a small trailer
  • Have sufficient driving range to reach my parent’s home 80 miles away even under less than perfect driving conditions, e.g. rain, wind, cold.
  • Have room for a reasonable amount of cargo even with a passenger or two.
  • Be capable of using public charging infrastructure.

Selection Process

While I knew pretty early on I was going to select the scion xB for my next conversion, I did do my usual research and compared a variety of similar vehicles.   My research validated what I already suspected which was the xB was well suited to EV conversion as it was substantially lighter than any of these other similar cars and despite being pretty boxy it was nearly the best aerodynamically as well.   Its only real down side was not a whole lot of room for batteries as so much of the car is interior space.  The vehicles I considered included the Scion xB, Chrysler PT cruiser, Pontiac Aztek,  Honda element,  Mazda 5, and Chevrolet HHR.   Of course there are other similar cars like the 2nd generation xB, the Nissan Cube and the Kia Soul,  but most of these were too new and thus too expensive, or I simply did not like them.

Build Process

Buying It

I bought the xB in June 2012 from a  sleazy used car salesman who was selling cars on the street in Portland.   He had bought the car from a chain smoker named Fred but had not transferred the title.   Anyway I paid cash for the car and after airing up the tires, checking fluids and a couple other minor fixes I drove it home from Portland to Seattle without incident.

Condition as Bought

My perfect xB was one that was white or green, had lowered suspension, and had a decent body and interior but high mileage or mechanical problems and thus would be cheap.    The one I ended up buying was about right in terms of mileage and body condition, and it is one of my desired colors and had lowered suspension.

The major downside to the one I bought was that it had been owned by a chain smoker, and the interior was very, very, soiled with nicotine funk.    The first thing I did upon getting the car home was tear out and steam clean the entire interior of the car.

On the positive side, this is one of the few cars I have bought that was actually able to drive home under its own power.


It took about 800 hours (estimated) and just about a year calendar time to complete this project to the point of being drivable.   The project included many phases, which are outlined briefly and roughly chronologically below.  For (much) more detail on the conversion process, visit the Construction page.

  1. Remove ICE Components:  Engine, Transaxle, gas tank, exhaust system, ECU, engine compartment wiring harness and clean engine compartment.
  2. Manual Steering Swap:  Replace the original power steering rack with a manual rack to simplify the build and improve efficiency.
  3. Drive Train:  Design a sub frame to hold motor, differential, inverter, and other engine compartment components in position and join them together using synchronous belt and custom CV shafts to get power from the motor to the wheels.
  4. Battery Boxes:  Locate, remove sheet metal from rear floor of the car, design and build 3 battery boxes:  a) “Mid” box under rear seat,  “Lower” box under rear floor, “Upper” box behind rear seat.
  5. Cable Conduit and Breaker:   Install high voltage conduit and high voltage DC breaker between the battery boxes and engine compartment.
  6. Electric Heater Core:   I am in cool, wet (9 months of the year, anyway) Seattle.  A working heater/defrost is necessary.
  7. Vacuum Brake System:   The original braking system of the scion is largely unchanged, but a new source of vacuum must be provided to power the brake booster.
  8. Rear Suspension Upgrade:   Heavier springs must replace the original TRD lowering springs, which would not carry the extra weight of 600lbs of battery.  Minor modifications to the rear axle beam spring hangers were also needed to increase clearance to the battery boxes.
  9. Inverter Installation:   This involved physically mounting the Solectria UMOC445TF inverter and routing cables to the passenger compartment and motor, and building a moderately complex interface board to allow the UMOC inverter to communicate with the driver (gas pedal, forward/reverse, indicator lights, etc) as well as communicate with the BMS and original systems of the car.
  10. DC/DC Converter:   Rebuild, Locating, Installing the DC/DC converter, which replaces the alternator by stepping down high voltage from the traction battery to keep the 12V battery and automotive systems such as lights, wipers, etc. running.
  11. Battery Installation:   Repackaging and installing the batteries,  adding insulation.
  12. BMS Installation:  Wiring, Interfaces
  13. Charger and J1772 Interface:  Installing the Manzanita Micro PFC30 charger and mostly-homebuilt J1772 and BMS interface components.

18 thoughts on “Scion xB EV

  1. mark yormark

    You mentioned you could do machine work with your engine lathe. What is the maximum diameter you can swing?
    Mark Yormark

    1. adstriminator

      Hi Mark- Max work diameter is 9″, max work length is about 26″. Accurate to about 0.001 in the hands of a pro. With me running it, and assuming its a pretty simple job, maybe 0.01

  2. David Rosenberg

    If I was willing to give up my back seat and therefore only two people in car, and wanted only partial electric, and limit my speed to 60 mph, would that change the time and cost .

    1. adstriminator

      partial electric would be HARDER that full electric, becuase now you have TWO full drive trains to manage. If you wanted to go this route, instead of trying to keep the xB ICE drivetrain and add an electric one, for example powering the rear wheels, I’d investigate if you could make a gen2 prius engine and transaxle fit into the xB somehow. This may be more feasible than it sounds as the xB 1nZFE engine is virtually identical to the prius engine and the cars were developed around the same time frame by toyota. The transaxle would be the main mechanical difference, the prius one of course has the electric motor assist. You would also end up swapping in the prius hybrid battery, prius ECU, all that wiring, and figuring out how to interface those components to the stock xB pieces.

  3. Scott Petersen

    Brian, I meant to ask about your vacuum pump at the ABFM. I saw you had a Hella vane type, and am wondering how loud it is. I have a Gast, which will probably last forever but is embarrassingly loud…sounds like a semi’s Jake brake. I’d like to change it out for something much quieter. Any information about alternatives would be appreciated.


      1. Scott Petersen

        That sounds (!) like the vacuum pump for me, Brian. Not sure I understand what the SSBC 28146RE relay is for, though. If the pump doesn’t hold a vacuum (as most pumps don’t), what’s the point of running after the limit switch opens? You state “This allows the pump to draw a full vacuum and prevents rapid cycling.” Think I’m missing something here.

        1. adstriminator

          The relay does two things: First, a typical vacuum switch cannot handle the amount of electrical current the vacuum pump motor draws, so the vacuum switch controls the relay coil, and the relay contacts switch the motor load. Second, this particular relay contains a small circuit that keeps the relay coil ON for several seconds after the vacuum switch turns off. Normal automotive relays do not do this. The reason is that if the vacuum pump turned on just above a certain amount of vacuum and back off just below the same amount, it would only run for a fraction of a second just as the vacuum went below that amount. The motor would chatter like a buzzer. This happened to me when I initially tried to use a different kind of relay in my last conversion. This is bad for the motor and does not work well. The delay (about 10 seconds) in the 28146RE relay lets the vacuum pump pull a much stronger vacuum than what opens the vacuum switch, so the pump does not need to run again until the brakes are pumped a few times or the system leaks down much later.

  4. Bruce Eisiminger

    Hi Brian,
    I am looking to do exactly what you have done. I love the XB and want to do an electric conversion as well. I have not bought one yet but am looking for an 04-06 first generation model. Thank you for your hard work and sharing it. Can a person buy a “conversion kit”? And what was the cost to do your build?
    Thanks so much!

    1. adstriminator

      Conversion kits are available for certain commonly converted cars, (S10,s VWs, Dodge neons, saturns, I know had kits offered from various sources at one time or another) but the xB I do not believe has a kit available. Mine is totally out in left field insofar as the mechanical setup.

      There are non-car-specific kits from several sources that give you everything but the adapter plate and batteries. They go by weight range of the car and desired horsepower.

      If you contact various EV parts suppliers who do adapter plates you will probably find they already have a design on file for the xB, as other xBs, toyota echos and xA’s have been converted, and they all have the same engine and transaxle.

      My build was “high end” so to speak owing to the large battery and AC drive. I spent about $20K on the conversion itself, not including the car.

      A more standard conversion using DC and with a 50-60 mile range might cost about $12K plus the cost of chassis.

      As nissan leaf batteries start appearing secondhand in greater numbers, you might be able to knock another 5k or so off those numbers.

  5. Saber Karain

    How can I implement the test box schematic, like yours, to control all switches?
    I have a Solectria ACGTX20 motor that I am building a controller for, and I am looking for specs on the motor’s encoder, and any schematics and data on the controllers used by it.

    1. adstriminator

      It is more or less impossible to find and original test box, but on the motor and inverter page at http://amphibike.org/blog/scion-xb-ev/scion-xb-ev-construction/scion-xb-ev-motor-and-inverter/ there are links to the solectria UMOC service manual. In the appendices to this it gives a circuit diagram with the 25 pin connector pinouts for the UMOC. It is easy to build a test box from this schematic. All you need is a 25 pin parallel printer cable, mating plug, a few LEDs, two 5K potentiometers and a few switches and a box to put it in.

  6. jeff warren

    I live in FL. no hills and plenty of sunshine. I was wondering if you ever considered putting solar cells on the roof of this vehicle, as it has the perfect roofspace for it. I am a newbie considering a build. In doing research I found you. The Xb is a favorite of mine.

    1. adstriminator

      Hi Jeff-

      Yes, the Xb is boxy enough you could probably put a 300W panel (they are roughly 3x6ft) on top without affecting weight or aero all that much, and in FL you certainly have the sunshine. However even in the best case scenario lets do the math: Florida gets 5.5 peak sun hours a day, or about 1.5kwh on that 300 watt panel, if it were perfectly aligned. A better assumption would be 200W, to account for shading and non-ideal alignment to the sun while driving. So now you are down to 1KW a day. And the charging system would lose a little bit too. Lets assume the step-up from 24V to around 150 to 300 depending on the car’s battery is 80% efficient. So now you are getting 800wh a day into your car’s battery. My xB gets about 250 wh/mile on average, so that is like getting about 3 miles a day from the sun. This assumes no extra losses from the weight or drag, and that the car is out in the sun almost all the time. No parking in that shady garage for you.

  7. Ormond Otvos

    Finally afforded an Xb 2004 just like yours. Have background in welding, electronics, and heavy machinery/marine repair.

    Have you considered the DAF system, the small Dutch car running a single engine with shafts on both ends driving two variable belt drives to two wheels, thus giving the differential and/or driving the rear wheels with the batteries in the front?

    The front wheels steer, the back wheels drive. No universals. One of the first automobile drive systems, using chain drive then.

    1. adstriminator

      Haven’t heard of the DAF system, but I can tell you a variable belt drive will likely be a lot less efficient than a modern CV joint axle, not to mention the extra complexity and wear issues. I did consider a dual motor/dual chain drive (one motor for each drive wheel, no differential but having the DC motors wired in series to make for an electronic differential) with my old MR2 conversion, but I ended up going the more conventional route for various reasons. I do have a belt drive in the xB, which now has 27,000 miles and zero problems, but it is a fixed ratio setup. The one major down side to it is that it is fairly noisy. It has gotten quieter as it has worn in, but it is still the noisiest part of the drive train.

  8. Yvan

    Are there any after pictures and performance stories? Curious as to what the interior compartment is like for you now, and how it’s handling based on your desired end results.

    1. adstriminator

      The interior is mostly stock xB. The only differences are I have an extra gauge pod on the dash with the ammeter, voltmeter, and 12V voltmeter, and a 7″ LCD touchscreen mounted over the glove compartment running BMS telemetry display software. The original automatic transmission gearshift lever is gone in favor of the control box you can see pictures of various places on this site, the main breaker is located on the tunnel centered between the front and back seats, and the deck is raised behind the back seat to make room for batteries and the charging system.

      Car has been running for 27,000 miles so far; in daily commute use since Nov 2014. Battery degradation negligible. Maintenance has been the differential pinion repair (which it probably needed before I even built the car), replacement of ONE cell, and a small amount of ongoiong maintenance to battery bus bars and the BMS.


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