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Ex-7 - Electric RX-7 conversion

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  • Ex-7 - Electric RX-7 conversion

    Hi,

    This is a continuation of what started as the "ElectraVan" project. The van lost it's suitability for a conversion and carputer platform, so I'm taking the components: Batteries, Motor, Controller, Charger, etc., and installing them in this cool 1988 Mazda RX-7 that I found with a bad engine. The project is moving quickly now, so I hope to be posting updates regularly until it's done.

    Here's the car in my buddy's workshop - he's doing all the mechanical updates for the conversion from stinky to clean electric drive:


    We wanted to get rid of the transmission completely, but we still need some kind of gear reducer and were unable to find anything suitable. So we kept the tranny for the time being, but got rid of the clutch & flywheel and direct-connected the motor to the input shaft of the transmission. Here's the motor installed and racks for 4 batteries above the motor and 2 more in front with the rack for the controller next to them:



    The car will have 20 lead-acid batteries: 10 in the trunk, 4 behind the seats in the area below where the top folds down (in former spare tire space. The Spare will be replaced with a can of fix-a-flat and a AAA card), and 6 in front. If we could get rid of the transmission and move the motor further back into the hump, we could have fit 2-4 more batteries in the front for better weight distribution. Hopefully that's a future mod. Here is a view looking behind the seats into the trunk area. The rack in the foreground is for 4 batteries behind the seats, and further back you can see the trunk, where we cut out the floor to lower the batteries as much as was could. There is a space just in front the the rack (see 4 studs?) Those studs will hold the battery charger, and the area to the left will hold the carputer and audio amplifier:



    Finally a view of the gutted interior. Series II RX-7's had a huge Pioneer radio in the center console. The lilliput will mount there along with a few other controls for the hybrid drive. I will also have a Labjack Data Aquisition Device (Similar to a Fusion Brain) that will manage and monitor all the EV Systems and provide status and control:



    That's it for now. I'm happy to answer any questions and I'll be posting a lot more as we finish the wiring and begin driving it.

    Shep
    Shep

  • #2
    Would love to see the pics. They are not showing.
    CAR: 2007 G35 Sport Coupe 5AT
    HARDWARE: Dell D630 w/ dock, internal 80G HD, internal 320G HD, Verizon Wireless Card, iBlue GM-2 GPS w/iGuidance, OBDPros w/DashCommand, Visteon HD Radio w/ Home Made Cable, Current Version of RR w/ DFX Skin. My Install.

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    • #3
      whats the motivation for this? the added weight of the battery would take a lot from the car's efficiency.

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      • #4
        drewbp - Um, not sure why the pics aren't showing up - I can see them. I'll check on it.

        Punky - we removed over 500 lbs from the car - engine exhaust, fuel tank, etc. and are adding about 1200 lbs of batteries and another 200lbs of motor, controller, etc.

        Here's the deal. I buy wind electricity at home. Electric rates are such that the energy required to drive a mile in an EV cost less than 1/4 the cost of an equivalent amount of gasoline. Since I'm using wind to charge the batteries, I will literally be driving on wind power at 1/4 the cost of gas. Does the extra weight make the car heavier and use more energy - yes. But it's way more than offset by the cost and environmental benefits.

        Details are on the ElectraVan thread, but this car will also have a part-time hybrid option. I'm hopeful that as an all-electric car, the EX-7 will get better than 100 miles on a charge. That will let me commute to/from work on a single charge with plenty of reserve. For longer trips, A very small trailer will carry a 30HP gas powered generator. It's not tested yet, but the generator will at least extend the range to 200-300 miles (Depending on speed, terrain, etc.), and hopefully will be sufficient to keep the batteries up for extended trips. If I don't need the generator, I can leave it at home.
        Shep

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        • #5
          From our programmer: sorry rob those attachments don't exist on the server. Whoever posted that will need to re upload them. Not sure why they never got uploaded but those attachments aren't there. Weird. I would love to see pics too.

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          • #6
            The Pictures

            Here they are:

            Click image for larger version

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            Attached Files
            Shep

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            • #7
              Hybrid Drive COntroller Screens

              If I have the pics thing working now, here are some screen shots from the controller program I've been developing. Data will come from onboard sensors and from a serial link out of the controller. It will be integrated and stored on the carputer, and real-time displays on the touch screen. The program I'm using will let me create a button to minimize it, allowing me to jump back to the front end if I want. I still haven't quite figured out about embedded aps in RR and I'm not up to speed on centrafuse. Any thoughts on using either of those with custom aps - seamlessly?

              Here's the splash page (I need to get a better pic of the actual car for this one):

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              This page has gauges for battery status. Top row is for the 240V main propulsion pack and the bottom row is for the 12V aux. battery:

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              This page is is an early stage of what I hope will be a useful performance / economy monitor. Each quadrant of the big bar graph in the middle represents energy flow to & from the battery pack and hybrid generator as well as regenerative energy during braking. Bottom graph will be a cumulative economy monitor:

              Click image for larger version

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              This screen will be a status for the generator, battery and controller/motor. Icons will be dynamic - will flash, change colors, or have a symbol overlay to add information. Pressing on any icon will go to a details page. I hope to have this pop up if there is an alert:

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              I'd love any comments on RR vs. Centrafuse as a front end to integrate with this....
              Shep

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              • #8
                Love this idea, but why lead acid vs the less waight/more power lithium ion?

                good luck.

                Mage
                =Cars=-
                2001 Kia Optima, V6 4matic fully loaded SE W00t! soon to have a Car pc.

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                • #9
                  very cool-- keep us posted!
                  My OLD 2001 Mitsubishi Eclipse GT:
                  "The Project That Never Ended, until it did"


                  next project? subaru brz
                  carpc undecided

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                  • #10
                    Wow, awesome project. With your batteries, how many Ahr in total reserve will you have? Also, what is the HP (or kW) rating of the motor that you plan on installing? I've seen some electric car projects, but they were mostly done on small pickup trucks due to the ability to carry more batteries in the back and get better range (despite the extra weight). Either that, or done on a super light car like a Geo Metro. An rx-7 will be interesting.

                    Your estimate of 100 miles per charge...that seems a bit low isnt it (for a typical electric car project)? After 100 miles, do you know approximately what depth of discharge your batteries will be at?

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                    • #11
                      Mage: I can sum up the decision for Lead Acid Vs. Lithium in one word: Cost. And availability. Cost and availability. Two words. Cost and availability and simplicity. Three reasons: Cost, availability, simplicity. Lithium batteries are not widely available and comparable in cost, and commercially available things like battery chargers & controllers are not necessarily compatible with them, off the shelf. For this reason, almost ALL EV conversions still use lead acid. This car will have regenerative braking - the motor will become a generator when decelerating and put energy back into the batteries. One advantage of L-A is that they can take in huge amounts of energy in the short term, an advantage for regenerative braking. If I had it to do over again, I would consider Absorptive Glass Mat (AGM) batteries rather than flooded Lead Acid. But the batteries I chose have about the highest energy / Lb and the highest energy / Cu. Ft of any commercially available battery.

                      Nobb: The batteries are 130 Amp-Hour which at 240 Volts = 31 Kilowatt-Hours. The motor is about 43 KW (peak) and can maintain about 18 KW continuous. That equates to about 41 HP peak or 24 HP continuous. But it doesn't equate to a car motor. A 3 phase AC motor like I'm using has high torque across nearly it's entire operating range. It makes in the 50-60 ft-lb across the entire range.

                      The truth is I really don't know what the range will be. I do know it will depend a lot on driving style - hot-rod starts and stops will have a huge effect on the range. I plan to test it and take measurements of the range.

                      One reason I bought the particular car I did was that it had been set up for autocross racing. The suspension is MUCH harder than a standard car - very heavy springs. I'm not happy about the weight in the back and I don't know how it will handle. But I don't expect RX-7 handling. I just want it to work! I do hope the mileage will be greater than 100, but the only way to find out is to drive it some.

                      Thanks for the questions - as this project moves on, I'm getting pretty excited to try it out!
                      Shep

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                      • #12
                        Originally posted by no_hazmats View Post
                        . . . I'd love any comments on RR vs. Centrafuse as a front end to integrate with this....
                        For me, Centrafuse has been a fine ready-right-out-of-the-box solution, because I'm not a programmer. RoadRunner/RideRunner was too much pain to configure; it was as if I was being asked to conduct an orchestra without knowing how to read music.

                        CF has a new plug-in architecture intended to help developers integrate their work with CF. With the retail price pf the program down at $75, that seems like a good deal for nearly no tweaking. YMMV, but I'm really happy with the new version.

                        EDIT: There's a developer's SDK available.
                        .
                        If just enough is really good, then too much ought to be perfect.

                        2006 Scion xB with in-dash Atom & Lilliput 889GL -- Worklog at http://www.mp3car.com/vbulletin/work...res-links.html
                        .

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                        • #13
                          Nice conversion...

                          Just as a tip for your battery management program...

                          A friend of mine have an electric Reva, that have a custom battery management program... There he can see voltage, charge and "status" of every single battery in the battery pack. (he have standard 12v 55mAh car batteries).

                          This proved quite useful when one of the batteries where dead, and the car acted quite strangely. Quick change of one cell and everything where back to normal

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                          • #14
                            I agree. I'm not a programmer either. The tool I'm using to build the hybrid controller is primarily graphical and menu driven. I'm slowing learning it's scripting language. I don't have the skills to do large scale SW development and I have to face that it's not something I am going to pick up easily.

                            That being said, I have been testing CF and RR and they both have advantages and disadvantages. The new CF is slick. And I agree about the pain to configure RR, although it seems more versatile and also seems to have a significant community of independent developers.

                            The tool I'm using on the Hybrid side is called DaqFactory, and a free trial can be downloaded from www.azeotech.com. It's primarily a SCADA tool (Supervisory Control and Data Aquisition). It can collect and store large amounts of info from a variety of sensors and do all kinds of data manipulations and statistics, etc. It also has a lot of control features - I will be able to use it to start & stop the hybrid engine based on battery status, etc. I'm sure a skilled programmer could build everything I want as an independent program on a microcontroller, but as I said, it's not what I do. I'm a hardware guy. I'm lucky to live pretty close to the world headquarters of mp3car. I'm going to stop in there today to see what new stuff they are testing and talk to them about front ends....
                            Shep

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                            • #15
                              Originally posted by Crinos View Post
                              Nice conversion...

                              Just as a tip for your battery management program...

                              A friend of mine have an electric Reva, that have a custom battery management program... There he can see voltage, charge and "status" of every single battery in the battery pack. (he have standard 12v 55mAh car batteries).

                              This proved quite useful when one of the batteries where dead, and the car acted quite strangely. Quick change of one cell and everything where back to normal
                              I know that Manzanita Micro makes such a system and it's a really good idea. I won't be able to afford to doit in the first iteration, but I hope I can add a BMS in the future, or if I do any future cars. Can you provide any info about the system they used. It's custom?

                              Thanks
                              Shep

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