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Thread: Ex-7 - Electric RX-7 conversion

  1. #41
    Low Bitrate no_hazmats's Avatar
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    Quote Originally Posted by 2k1Toaster View Post
    I am concerned as others have mentioned with your choice of SLA batteries and lots of them. That gets really really really heavy and innefficient. Also I dont see these as deep cell either? Are they really average everyday walmart special SLA? I would start a li-poly fund to be cashed in sometime next year or the year after.
    The weight is a concern. But this choice wasn't made without a lot of consideration. The three primary things to think about in choosing batteries are:
    1. Weight Denisty - The number of Lbs per watt-hour of energy the battery provides'
    2. Volume Denisty - the number of watt-hours per Cubic Inch of volume the battery takes up,
    3. And Cost Density - watt-hours per $ of battery cost.


    The idea is to get the maximum amount of energy storage per unit of weight, volume, and cost. There are also technical considerations: The ability of the battery to absorb and give up energy at the rate that a car requires, the availability, and environmental concerns.

    So we assessed dozen's of batteries on 2 of the primary considerations: Weight and volume density. The batteries we chose rate very highly in terms of both factors. If I get rid of batteries I would lose a large amount of available energy for each one deleted. And if I went to different batteries (Lighter ones for example) I would also lose energy. Because the top choice in terms of Volume and Weight density were within our budget, I didn't do a detailed analysis of costs on all battery choices.

    The batteries are from a company called Crown Batteries. The original model we chose was from a company called US Battery, model 31 TMX. It is a true deep cycle battery, and not a marine or wal-mart type of battery. I talked to US Battery and discovered that the 31 TMX were being manufactured under license by Crown. When I ordered them from a local distributor, I told them that I would take either the Crown or the US Battery versions since they were the same anyway. They could get the Crown Batteries immediately and the US Batteries had to be special ordered, so The Crown batteries are what I got. Here is a cleaned up version of the spreadsheet I used to assess batteries on weight and volume densities. In either column, you might see some models that beat the 31 TMX on one or the other factors, but not many that beat it on both:

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    By the way, Students at Morgan State University EE department were instrumental in putting together this assessment and gathering information. They've also been working on a design for the hybrid power system as a class project.

    We didn't assess lithium batteries for three reasons: First, a year and a half ago when we first started this, I considered lithium technology to be too expensive for our budget. I'm not sure how that's changed since then. Second, an assessment of commercially available battery chargers for Lithium batteries showed ZERO products to support them. We're not talking about a laptop charger here! A reasonable EV battery charger provides 20 to 40 AMPS at 240 Volts with a greater than 90% efficiency. The hybrid system has to be compatible with the battery technology too. I know that I can make something for the hybrid that will work for LA, but lithium is a big unknown. I'm just some guy working in a garage. I'm not Toyota, I don't have an RD staff to figure these things out, so I need to eliminate variables that I cannot easily manage. Finally, traditional Lead Acid batteries were recommended by the distributor of the system and they have a great deal more experience than I do in these things.

    As a final thought, the environmental consideration is very important to me. With words like 'Lead' and 'Acid', we might think that L-A batteries are an environmental travesty. But there is a thriving industry that ensures that 100% of LA batteries are easily recyclable, and in fact, battery recycling is required by law in most states. The lead is re-used for new batteries, the cases are made if recyclable plastic and even the acid is salvaged. In the case where a battery breaks or leaks, yes the acid can be dangerous, but it is easily diluted with plain old water, and will be neutralized in the soil. I honestly don't know about the environmental impact of Lithium technologies. I hope they are as recyclable as LA are, but as a newer technology I know the infrastructure to recycle them doesn't exist on the same scale as for LA batteries.
    Shep

  2. #42
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    Fiberoptic's Avatar
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    Wow - that is a detailed analysis - Would you be willing to share that spreadsheet? Maybe we can turn that into a live "wiki" type web app that others can contribute to and update. posssibly with newer battery technology as it becomes available. After we take a look at the spreadsheet I will talk with one of our software guys.

  3. #43
    Fusion Brain Creator 2k1Toaster's Avatar
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    Lithium batteries are definately more dense, much more costly, much lighter, slightly worse environmental impact, longer lifespan, and much more difficult to charge.

    I have done lithium charging small scale and know of the large scale charging. Ask me again in a year or so, and I will be able to say more on the subject.
    Fusion Brain Version 6 Released!
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  4. #44
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    You guys are so smart lol.
    "The text that you have entered is too long (12638 characters). Please shorten it to 10000 characters long."

    Dam it!

    "The text that you have entered is too long (10418 characters). Please shorten it to 10000 characters long."

  5. #45
    High Voltage blk02si's Avatar
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    project is looking good, nice battery analysis!!
    Build Things, it keeps your brain busy.

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  6. #46
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    Update - the car is home

    Worked all day today on the car. Will post pics over the weekend.

    Finished all the control wiring.

    Fabricated about 30 battery interconnects of #2 AWG wire and hooked 'em all up. It's scary working with 240 VDC. Deadly voltage. We were careful and no problems.

    Connected the battery charger, and it quickly told us the batteries were around 80%. We charged them for a few minutes while connected other things.

    Picked up the car trailer to drag the thing the 90 miles back home.

    Began the process of trying to spin the motor. Found a couple of wiring errors and fixed them, still no luck. The book says the next step is to dig into the software console for the controller. But wait, it's 6:30 on New Year's Eve and I'm 2 hours from home, and we still need to clean up and get the thing on the trailer. Better leave it for the weekend.

    Not really bummed about that. It's probably not a good practice to work on something when we're so tired and too close to it all day. If it's still a wiring bug, it will probably be more apparent in the light of day to a rested brain. If I need to reload the SW and parameter files, I definitely need to study up on that first.

    Dragged the car home to find a happy family and a warm crackling fire. Thank God the temps stayed above 32 and the roads were only wet, not icy.

    Home at last:

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    The plywood covers are just temporary protection from the HV areas:

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    Home is where the hearth is....

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    Assuming it gets running without too many additional problems, starting next week I will:

    • Clean up the propulsion wiring, and lace everything together neatly,
    • I need to install a 240V, 20A outlet on the side of the house near the driveway for charging. Luckily I have a subpanel in the Laundry Room right by the driveway, so that should be easy,
    • Fabricate nice clear plastic covers for the control board and the battery tops,
    • Begin installing the audio and computer systems,
    • Install the LabJack (Similar to Fusion Brain) and sensors,
    • Install door lock actuators, speakers, Sirius & GPS receivers, etc.,
    • At some point take it for State inspection and get license & Insurance.


    I look forward to getting to the areas that are the focus of this forum. I appreciate all the positive comments and will try to live up to the expectations.

    Tiberius has the right idea. I think I'll join him:

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    Happy New Year.

    Let's Go Mountaineers!
    Shep

  7. #47
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    You might want to add the odyssey dry cells to your battery spreadsheet. I used one of these for about a year and a half. I would again if they weren't so expensive.

    http://www.odysseybatteries.com/

  8. #48
    Low Bitrate no_hazmats's Avatar
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    USB too much???

    Well, the car is in the driveway. I haven't worked on it since New Years eve. Temps in the teens & twenties and 40 mph wind have been a factor.

    So I set up the computer that I got several months ago from MP3car and have been playing with RR and loading drivers and software for all the assorted accessories. I'm gonna need a couple of USB hubs.

    Here are my USB devices:

    # USB Device
    1. Bluetooth Adapter
    2 802.11 Adapter
    3 Front Camera
    4 Rear Camera
    5 Microphone
    6 Sirius Adapter
    7 EV Ctl. USB-to-Serial
    8 OBDII Adapter
    9 Volume Knob
    10 Cell Phone
    11 CD/DVD Player
    12 Data acq. & Ctl Device
    13 GPS Receiver
    14 Touchscreen

    Is this too much?????
    Shep

  9. #49
    Fusion Brain Creator 2k1Toaster's Avatar
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    make sure you use powered USB hubs, and not passive ones.

    Quote Originally Posted by no_hazmats View Post
    Well, the car is in the driveway. I haven't worked on it since New Years eve. Temps in the teens & twenties and 40 mph wind have been a factor.

    So I set up the computer that I got several months ago from MP3car and have been playing with RR and loading drivers and software for all the assorted accessories. I'm gonna need a couple of USB hubs.

    Here are my USB devices:

    # USB Device
    1. Bluetooth Adapter
    2 802.11 Adapter
    3 Front Camera
    4 Rear Camera
    5 Microphone
    6 Sirius Adapter
    7 EV Ctl. USB-to-Serial
    8 OBDII Adapter
    9 Volume Knob
    10 Cell Phone
    11 CD/DVD Player
    12 Data acq. & Ctl Device
    13 GPS Receiver
    14 Touchscreen

    Is this too much?????
    Fusion Brain Version 6 Released!
    1.9in x 2.9in -- 47mm x 73mm
    30 Digital Outputs -- Directly drive a relay
    15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
    Buy now in the MP3Car.com Store

  10. #50
    Low Bitrate no_hazmats's Avatar
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    Quote Originally Posted by CapnBoost View Post
    You might want to add the odyssey dry cells to your battery spreadsheet. I used one of these for about a year and a half. I would again if they weren't so expensive.

    http://www.odysseybatteries.com/
    The Odyssey batteries look to be extremely tough, but are cranking batteries. Their numbers don't stack up to deep cycle batteries. Only the PC-1800 comes close to the middle of the pack....
    Shep

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