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Thread: Ex-7 - Electric RX-7 conversion

  1. #61
    Low Bitrate no_hazmats's Avatar
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    Max Range Thoughts

    I don't know if I agree that running it off the wheels will give meaningful information about range. Power = Volts x Amps. It will take many more amps to move a 3500 lb car 50 miles than it will take just spinning the wheels the same number of turns.

    Right now I don't have the batteries enclosed or insulated, don't have them heated (Which I doubt I'll do), and it's 18 degrees outside! I won't get nearly the range that I will in the summer. Furthermore, Lead Acid batteries need to be exercised before they meet their max capacity. From what I've read, it takes about 30 to 50 charge / discharge cycles for them to get to max. After that they gradually degrade over time.

    I don't want to ever kill the batteries to the extent the car won't go. There is a trade-off between how deeply discharged they go and how long they last. Probably never want to go below about 50%. The controller has a lower limit of battery voltage, under which it disables the drive anyway. Too deep of a drain really kills battery life.

    My plan is to start out with short hops around the neighborhood and never go more than 3-4 miles away. I'll start out putting no more than 20-30 miles on it and monitor the battery voltage. As it starts to drop to anywhere near the limit I'll head home for a recharge. As soon as I'm confident, I'll start driving it to work - I can also recharge it there. It's about 17 miles each way. When the weather starts to warm, I'll get more range and the batteries will begin to be broken in. Based on conversations with people that have the same system on similar cars, I expect 60 to 100 miles.

    Another factor is where / how the car is driven. I live in a rural area near a couple of rivers. So there's a good bit of up & down terrain. That will be different than straight & level. I expect range will be different at 65 mph on a highway than at 35 mph on country roads too.

    I will try to set up the GPS to record trips so I get an accurate distance measurement and speeds.
    Shep

  2. #62
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    Congrats

    If you haven't looked at the OBDII logger, please do. You can plot your battery data against the speed and gps data with it

    http://www.mp3car.com/vbulletin/obdii-gps-logger/

    I assume once you put a decent number of miles on it (say 20) you could extrapolate reasonably accurately to get you max range (keeping the batteries above 50%). I hope you prove us wrong, but I'm still skeptical about your expected range.

  3. #63
    Low Bitrate no_hazmats's Avatar
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    Quote Originally Posted by cgalpin View Post
    ...If you haven't looked at the OBDII logger, please do. You can plot your battery data against the speed and gps data with it.
    Wow! This is great. It looks like I can run it under windows using a linux simulator?? Does anyone know if this could be embedded within RR? Even if it runs as a separate app, that would be fine.

    I've mentioned in the past that all things SW are somewhat elusive to me. Do you think anyone would be able to assist in moving the data from the SW I'm using into the GPS Logger to record Watts, Amps, etc agains the GPS Data? I know there are ways to access the data from other programs, and I have all the documentation, but I get lost somewhere between global variables and def_lib_whatevertheheckyoudonext. That is to say ... HELP!

    Anyway, I'll download it into the car computer when I get some time this weekend and begin playing with it and setting it up with my GPS receiver. Thanks for the suggestion. If I had time to read this entire forum, that would mean I have nothing else in the world to do. Sigh.... Someday.
    Shep

  4. #64
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    I'd post up for help in that forum and I am sure someone can help you out. I never got my obdii reader working under linux and haven't had time to get back to carputer stuff in months. But it looks like someone built it under cygwin and ran it on windows.

  5. #65
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    Quote Originally Posted by no_hazmats View Post
    But the batteries I chose have about the highest energy / Lb and the highest energy / Cu. Ft of any commercially available battery.
    You do realize that no LA has anywhere near the energy or power density of Lithium Ion so I assume you mean these are nice compared to LA batteries.

    A good choice for a cheap quick conversion is the blue top style optima cells.

    If you want to swap to lithium ions later you could try the thunder LiFePO4 based cells. They are relatively cheap. Getting the chargers, balancers, and so on really is not that big a deal compared to the work you already did. http://cgi.ebay.com/Prius-Plugin-Con...item2c5065c924 Lots of people are selling kits like that now (I think the batteries are made by a chinese company called thunder sky battery or something). I haven't tested those specific batteries, but I have tested many others. It is really obvious that if you want decent range and actual usability (cycle life) you will have to move past LA batteries. Another cheap option is to scavenge prius batteries and use a bunch of them instead.

    BTW that isn't your rav4 is it? I think I recognize it

    You do know that most regular LA batteries die extremely quickly under high DoD scenarios right? You will lose significant capacity in less than 100 cycles if you do that.
    As far is range is concerned you could calculate some rough ideas easily.

    Find the force to over come rolling resistance, and the Cd then make some calculations to see what you could do at a constant speed. That will give you an upper bound and you will know you can never do any better than that.

  6. #66
    Low Bitrate no_hazmats's Avatar
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    Quote Originally Posted by sxott View Post
    You do realize that no LA has anywhere near the energy or power density of Lithium Ion so I assume you mean these are nice compared to LA batteries.
    Yup, I'm aware of that. In my statement that you quoted, I should have specified that I was referring to Pb technology - FLA's and AGM's. I chose FLA's based on a number of factors I've already explained. No intention of dis-ing or rejecting LI technology. Just simply chose FLA at this time.

    Quote Originally Posted by sxott View Post
    A good choice for a cheap quick conversion is the blue top style optima cells.
    Optima's are known to be great batteries. The D34M has a Volume/Power density of 1.23 WH/in3 and a Weight/Power Density of 15.17WH/lb as compared to 1.73 and 23.67 respectively for the FLA's I'm using; so they don't come close to heavy duty FLAs in terms of energy capacity. I did not take estimated lifetime into account, however, and that's a factor to consider more fully if I don't go with LI in the future.

    Quote Originally Posted by sxott View Post
    If you want to swap to lithium ions later you could try the thunder LiFePO4 based cells. They are relatively cheap. Getting the chargers, balancers, and so on really is not that big a deal compared to the work you already did. http://cgi.ebay.com/Prius-Plugin-Con...item2c5065c924 Lots of people are selling kits like that now (I think the batteries are made by a chinese company called thunder sky battery or something). I haven't tested those specific batteries, but I have tested many others.
    I'm excited to learn more about LI batteries. I'll look into those when I get time!

    Quote Originally Posted by sxott View Post
    Another cheap option is to scavenge prius batteries and use a bunch of them instead.
    I simply don't have time to find / test / assess a bunch of scavenged batteries. Sounds like a business opportunity for someone

    Quote Originally Posted by sxott View Post
    BTW that isn't your rav4 is it? I think I recognize it
    Nope - Pulled the pics off the interweb. I think that Toyota delivered many identical RAV-4E's in California all the same white.

    Quote Originally Posted by sxott View Post
    You do know that most regular LA batteries die extremely quickly under high DoD scenarios right? You will lose significant capacity in less than 100 cycles if you do that.
    DoD?? In any event I don't intend to kill the batteries prematurely.

    Quote Originally Posted by sxott View Post
    As far is range is concerned you could calculate some rough ideas easily.
    My calculations, using various EV tools out there considering vehicle weight, battery size, Drive type etc.; came out to anywhere between 80 and 100 miles. My conversations with people who have converted and are driving similar cars (Porsche 914's) with identical drive system and similar Flooded LA's suggest that the online calcs and estimates are overstated. Scaling one guys real-world experience to my battery capacity (not accounting for weight or any other differences) suggested 78 miles. He gets 60 miles with a smaller (lower voltage lower WH FLA) pack. I think he was told by the supplier to expect over 100.

    Quote Originally Posted by sxott View Post
    Find the force to over come rolling resistance, and the Cd then make some calculations to see what you could do at a constant speed. That will give you an upper bound and you will know you can never do any better than that.
    I think that "Force to over come rolling resistance" might be too simplistic. Yes you can get a theoretical upper limit, but it doesn't take into account start / stop, regenerative energy, losses, terrain, speed, or many other factors. So I don't really know what value there is in knowing that theoretical upper limit. I just want a car I can drive to/from work and to green events in may area that will promote EV's and renewable energy in general.
    Shep

  7. #67
    Low Bitrate no_hazmats's Avatar
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    Quote Originally Posted by aldogrech View Post
    Hi,

    Thanks for all the contributions to this Blog. I am at the early stages of building what I believe is the first Citroen DS EV (amanoauto.blogspot.com) and reading your Blog has been extremely helpful.

    Thanks, Aldo.
    Aldo,

    I'm sorry, for some reason I missed your post. Thank you for the comments. I look forward to following your blog. If you haven't already been there, check out the EV forums at the DIY Electric Car Site. I wish I were posting more detail - especially from the earlier stages. But the car was at my friend's house about two hours away from my home, and he was moving a mile a minute.

    I really wish I could avoid all the petty details of life - going to work, keeping the house up, planning & hosting my daughter's college graduation party (Well, not that one - I'm terribly proud of her!), and just work on the car. Since I drove it for a few moments a couple of days ago, it kills me to walk past it in the driveway and not get in it and take it for a test spin! I did make it to the Motor Vehicle Admin at lunchtime yesterday to get the title transferred and get temporary tags for it and I have an appointment set up with a friend who is a licensed state safety inspector to come by my house to give it the safety inspection (I don't want to risk the 50 mile round trip just yet!). House call for safety inspection! I love it!

    The weather finally broke around here to 'normal' winter temps - lows at night just below freezing and highs in the 40's (F). Makes it easier to work on the car. So, on Sunday I plan to

    • Connect the analog Volt & Amp gauges;
    • Finish some wiring clean-up;
    • Bolt the driver's seat in;
    • Take it for some test drives;
    • (Hopefully) mount the PC and begin running power & A/V wiring;
    • Play with some of the SW I've been downloading;
    • Actually mount the charging outlet to the wall of my house rather than have it hanging by the wires!;
    • Document & post what I'm doing here in the worklog.


    And maybe by then I'll mention the unique, exciting, and embarrassing way that I broke my very nice Lilliput 7" transflective touchscreen. And also the repair which I hope to accomplish this weekend too. Hint: The repair DOES NOT involve superglue. Or does it?
    Shep

  8. #68
    Low Bitrate no_hazmats's Avatar
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    Further out plans

    I have another family event the following week. After that my weekends clear up. So, my friend Ron is planning to come down then and help wrap up a lot of the mechanical stuff.

    (About the Carputer): I've avoided posting too much about it here on the forum. I have nearly everything in hand and it's been set up on my desk for months. I just can't focus too much on that at the same time as all the mechanical & propulsion stuff. I'll begin posting some pics and background and plans for that soon - I promise. I think it will be a 'typical' setup except for the I/O where I'm using the LabJack instead of a FusionBrain. And some of the EV / Hybrid stuff that's unique. I'm working on some schematics and laying out a plan for installing everything, but it's pretty much back-burner at the moment.

    Anyway - here's the list of big things we need to do in order to call it more or less 'finished':
    • Finish the wiring - a few components such as the DC/DC converter, exhaust fans (To vent battery gasses when charging), gauges & car instruments need to be completed.
    • Thoughtfully plan and install all the carputer components. This car may not be the most showy car when it's done, but I want it to be clean, neat and professional, and to do all the things I want it to do.
    • I have been designing the circuits to measure the High Voltage stuff. It's challenging because the battery pack is isolated from the car chassis (i.e. it 'floats' relative the car ground.) But the A/D converter is referenced to the computer ground which is connected to the car ground. That means if any part of the battery wiring shorts out to ground, the current will try to flow through the DAQ - not generally good for it. A simple way to do it is to tie together the reference on the A/D and the (-) side of the battery pack through a high value resistor (like 500,000 ohms). That will limit any current should a short circuit happen, and will skew the measurement a few millivolts under normal conditions. Still need to do the math to make sure everything is right, but I think it will work. A few MV is nothing when measuring on a 300 V scale, so I don't care about the skew. The alternative is an expensive signal conditioner that I really want to avoid buying.
    • Install the new carpet set.
    • Fabricate an interior cover for the batteries that are behind the seat. Will probably use 1/4" or 3/8" plywood and the original cover for the same area when the spare tire was in there. It's 4-5" higher now though. I have spare carpet fabric to cover the new parts. That area is open to the trunk and will vent through it.
    • Make acrylic panels to cover the batteries in the trunk& under the hood. Exhaust fan for the trunk is mounted but I need to make duct work and wire it up too. It will come on automatically whenever the charger is plugged in to vent out the hydrogen gas (and the sulfur stink) from the batteries.
    • Fabricate and install covers for the exposed part of the battery rack. Right now the batteries are exposed to the road below what used to be the trunk floor. I'll use some kind of sheet plastic or FRP for that.
    • Fabricate acrylic panels for the batteries and relay board under the hood. 290 VDC is Deadly! Also I want it to look decent for when we show it at places.
    • Finish installing the DC/DC converter.
    • Remove the final vestiges of the factory wiring that's no longer used. It's hard to do that when it's too cold -the bundles are very stiff.
    • Put on a new convertible top. I'm not certain I'm up for that. The RX-7 has a weird convertible / Targa top with a glass window. I'll probably have to bite the bullet and take it to someone who knows what they're doing.
    • Get it detailed and maybe some more finish body work. It has a few dings - it's 22 years old!
    • Finally, install the generator set on the little trailer and build a little body over it.


    I also need to take the engine and all the parts that came with it and list them on Craigslist or eBay to collect some money back. I still need to purchase the Manzanita Micro charger to interface between the generator and the drive system/ $3,300 is way outa my budget, but I should be able to make a substantial portion of that from selling parts.

    So, um, that's the plan.
    Shep

  9. #69
    High Voltage blk02si's Avatar
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    Sounds like you have a good plan setup. The real benefit is when you can start driving it around, to work, on the weekends, etc. Make it a reliable form of transportation and it will pay itself back.

    Split loom all the cabling on your floating battery array and you should be covered from shorting to ground. OEM's use quite a bit of it in the engine compartment, steering column and the like, pretty much anywhere there are moving parts. It works for them so I would consider it a cheap investment to protect you digital acquisition parts.
    Build Things, it keeps your brain busy.

    AutoPC v1 (Retired) - AutoPC v2 (in progress) - www.shocknet.us

  10. #70
    Low Bitrate no_hazmats's Avatar
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    1st road test

    It was up to nearly 50 degrees today. So I bugged out of work to take it for a test drive on a real road.

    1st chore - fix an annoying bug. When I first drove it on the driveway, when I would apply the throttle, it would more often than not make a bit of movement then cut out. There were a slew of fault codes (all the same fault) on the controller. Traded some emails with other Azure system owners and I learned that it's generally considered a spurious fault that reports noise / bad ground of the controller. Since we had grounded it properly, and other have experienced exactly the same thing, I did what they did and disabled the fault report for that particular fault. Problem went away.

    Took it down a little residential street and got it up to 30 mph with no issues.

    Took it a couple of miles down the main road (A rural road) by my house, and got up to about 40 mph in 2nd gear, and went up 3rd for a while. (it's a 30 mph zone). After about a mile or so I turned around and headed back. Got it up to 50 in 3rd, and shifted to 4th. Not much power in 4th but it seemed to hold it's own before I got to a curve and had to slow down. The motor has good torque to well over 5000 RPM (11,000 is the limit), so going fast in 3rd isn't a big deal.

    Impressions: No vibrations in the drive train

    Not a problem starting off without a clutch. Just a bit slow at the very start.

    Shifting up / down without a clutch is NO problem. Just lift the throttle and shift.

    Rear suspension is not sagging. VERY tight with the KYB shocks on the highest setting. May need to back them off a bit.

    Overall I'm a happy camper. Will drive it more on Sunday.
    Shep

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