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  • mauswerkz
    replied
    Originally posted by brent012 View Post
    Ahh cool, so you'll have a pc in there for that display basically? Ever thought about using a cheap head unit from ebay/china which has windows ce on it for the display then? You'd have to use an older version of VB i'd say but it'd all work good as long as you could connect up an input from that main microcontroller, would be real easy to install in to the car as well then - but that's the least of your worries
    I'm planning to interface the battery management system and other key EV parameters/controls via either a carputer, or one of those chinese headunits running android (or infact any android tablet that the user wanted to mount in the dash for navigation, music, etc).

    Originally posted by brent012 View Post
    Lol sorry if what im saying is completely pointless or irrelevant, i don't know too much about electronics = ( I have an interest in it though and im starting uni this year doing ICT Engineering/Business though! Will be specialising in software but i still get to do some electrical engineering stuff and embedded systems too
    Congrats on starting uni! Software is fun, I think. Now that the hardware of my projects is mostly ironed out, the development is (and has been for a while now) all in software. There are many lines of code making everything work, talk, and play nicely (and not explode).

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  • mauswerkz
    replied
    Originally posted by tekkentool View Post
    Yikes! I knew EV batteries were expensive but damn. Even the DIY route isn't cheap.
    Yeah, they're pricey, but if they aren't abused, a modern EV battery should last 5-8yrs, which is about the same age you'd expect to start needing to do major work on any car. Also, the replacement battery in 5-8yrs will be half the cost and twice the capacity of the old one anyway.

    Regardless, I've done the math and taking into consideration the cost of the battery, the cost of electricity, and the cost of E10 petrol today, you'll break even on the cost of the battery if you drive an average of 44km/day (if the battery lasts 5yrs) or 28km/day (if the battery lasts 8yrs). Either of those numbers is reasonable. Luckily, the average distance per day and expected battery lifetime are linked, so if you drive less per day, the battery will last longer, and vise versa. I don't drive my car much at all. Maybe 2-3 days/yr, and my commute is only 10 minutes each way on days that I work, and I still manage an average of 29km/day according to my tracker app on my phone. Any driving beyond those averages ends up actually SAVING you money in the long run over fuel, and that's assuming you'll have to replace the battery.

    For example, if you maxed out the car's range every day (95km/day or so), assuming the battery would only last 5yrs, and that electricity will stay at $0.25/kw-hr and that petrol will stay at $1.40/l, you'd STILL save $38/wk over that period of time over driving a car that gets 10l/100km (even at 6l/100km, you still break even). That's almost $2000 saved per year. Over 5yrs, that's $10,000, enough to buy a new battery at today's prices. So the battery can potentially pay for itself.

    It's also safe to assume that both fuel and electricity prices will go up over that period, but it's more likely that fuel will go up at a faster rate. Throw in the fact that a modest investment in solar panels for your house pays itself off very quickly these days and an electric car suddenly doesn't seem as expensive.

    Okay, I'll stop preaching now ;-)

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  • brent012
    replied
    Originally posted by mauswerkz View Post
    Embedded C is the reason I'm so comfortable with C ;-)

    There are 99 microcontrollers being used in that system (not kidding, one on each cell managing the cell's voltage during charging, and one polling the rest for their data and doing all the calculations). It's scalable up to 250 cells. The before/after picture is a shot of the serial stream coming directly from the main microcontroller. I've hooked an LCD up to it (simple 2x16 one) before and that's how it will be in the car for showing critical information (low cell voltage, high cell temperature, state of charge, etc).
    Ahh cool, so you'll have a pc in there for that display basically? Ever thought about using a cheap head unit from ebay/china which has windows ce on it for the display then? You'd have to use an older version of VB i'd say but it'd all work good as long as you could connect up an input from that main microcontroller, would be real easy to install in to the car as well then - but that's the least of your worries

    Lol sorry if what im saying is completely pointless or irrelevant, i don't know too much about electronics = ( I have an interest in it though and im starting uni this year doing ICT Engineering/Business though! Will be specialising in software but i still get to do some electrical engineering stuff and embedded systems too

    Leave a comment:


  • tekkentool
    replied
    Yikes! I knew EV batteries were expensive but damn. Even the DIY route isn't cheap.

    Like anything I guess the cost will drop and efficiency increase...I mean look how far mobile phones have come in 20 years.

    Leave a comment:


  • mauswerkz
    replied
    Originally posted by tekkentool View Post
    So curious question, how many KM's of range did you design and plan the battery cell in this to last for? What is the ballpark you're aiming for?
    The pack I've built here is only 1.25kW-hr. It's just a "high" voltage, high current power source for short full-power tests of my motor controller (sized with dyno runs in mind). If I put it in a car, I would get about 7-8km on a charge at 60kph.

    The pack that will eventually end up in the car will take me 100km on a charge at 100kph average speed. More at lower speeds and probably another 5-10% thanks to regeneration when braking and going down hills. That pack will be 19.2kW-hr, more than 15 times the size of this one.
    Last edited by mauswerkz; 28-01-2012, 09:41 PM.

    Leave a comment:


  • tekkentool
    replied
    So curious question, how many KM's of range did you design and plan the battery cell in this to last for? What is the ballpark you're aiming for?

    Leave a comment:


  • mauswerkz
    replied
    Originally posted by brent012 View Post
    So you are going to be using an actual PC with it? How about using Embedded C so you can have a microcontroller? Might have to read this whole thread lol, i saw the photos before but never took the time to read all the pages.
    Embedded C is the reason I'm so comfortable with C ;-)

    There are 99 microcontrollers being used in that system (not kidding, one on each cell managing the cell's voltage during charging, and one polling the rest for their data and doing all the calculations). It's scalable up to 250 cells. The before/after picture is a shot of the serial stream coming directly from the main microcontroller. I've hooked an LCD up to it (simple 2x16 one) before and that's how it will be in the car for showing critical information (low cell voltage, high cell temperature, state of charge, etc).

    Leave a comment:


  • brent012
    replied
    Originally posted by mauswerkz View Post
    I wrote that software, yeah. It's done in Visual Basic, though I'm more comfortable with C than Basic these days (Was good with Basic when I was much younger). I haven't had a good play with Visuall C++ yet, so I'm using what I know for the moment.
    So you are going to be using an actual PC with it? How about using Embedded C so you can have a microcontroller? Might have to read this whole thread lol, i saw the photos before but never took the time to read all the pages.

    Leave a comment:


  • Dreamz
    replied
    Originally posted by Marty View Post
    speed controller for an electric car

    PS: your pic chip is missing from the socket
    you beat me too it marty .. i knew as soon as i seen it..
    been racing rc cars since i was like 12

    Leave a comment:


  • mauswerkz
    replied
    Originally posted by GakkenGod View Post
    I'm just curious what is the estimated cost of your project. It is very motivating.

    I have looked into tesla roadsters and such and am very impressed with the advances in tech.

    Also do you know what motor you plan to use?
    Estimated cost of parts is listed below:
    Car: $5000 (my 1992 BMW 318is)
    Motor: $1850 (details here: http://forums.mightycarmods.com/show...l=1#post102659)
    Controller: $???? (I'm designing it myself and development has been very expensive/time consuming. Retail price will be around $4000)
    Batteries: $9000 (Current plan is for a battery pack that will get roughly 100km range
    Charger: $800 (Not sure if it will be an off-the-shelf one, or my own design. Will likely give it a shot myself so that it can talk to the BMS and other components designed by me)

    Originally posted by Jenga View Post
    That's really cool dude, did you make the PC software that outputs the different cell voltages? And I'm assuming you're charging the batteries in mini-banks of 3 cells (since it's 3.6V)
    I wrote that software, yeah. It's done in Visual Basic, though I'm more comfortable with C than Basic these days (Was good with Basic when I was much younger). I haven't had a good play with Visuall C++ yet, so I'm using what I know for the moment.

    I'm charging the batteries with the rectified output of a 0-280vac 2.5kW variac. So far I've charged them in strings of 40 cells in series, 4 cells in parallel (that's what the screen shots above are from). Once I get the packs mounted safely and properly wire up, I'll be able to charge the entire 320v string at once with my variac. It requires supervision at the moment as the output is not regulated and it fluctuates as the mains voltage varys. Initial current is 6A, reduced to 250mA (well within the BMS's bypass capability) once the first cell reaches full charge. This is done manually by me at the moment, but will be done by a proper charger eventually. Luckily, it only takes about an hour to charge the pack this way, so no big deal.

    Leave a comment:


  • Jenga
    replied
    That's really cool dude, did you make the PC software that outputs the different cell voltages? And I'm assuming you're charging the batteries in mini-banks of 3 cells (since it's 3.6V)

    Leave a comment:


  • GakkenGod
    replied
    I'm just curious what is the estimated cost of your project. It is very motivating.

    I have looked into tesla roadsters and such and am very impressed with the advances in tech.

    Also do you know what motor you plan to use?
    Last edited by GakkenGod; 28-01-2012, 05:37 PM.

    Leave a comment:


  • mauswerkz
    replied
    Finally got the battery management system (BMS) installed on this test-pack. As before, there's 98 cells in series, 4 in parallel. The battery pack will be used for testing my EV motor controller. Eventually, the BMS, motor controller, and a few other products will be for sale to people who want to do their own electric car conversions.

    Here's a pic of the system fully installed on the battery pack.


    For those not clear on the purpose of a battery management system, here's an example. On the left is the voltages of each cell in a 40-cell series string of batteries. You can see clearly that they are all different and not "balanced" with each other. On the right is that same string of batteries after charging with my BMS installed. Notice how every cell's voltage is very close to the rest. They are well balanced.


    If I had attempted to charge that string of batteries without a BMS, the highest cells (69,79,81) in the string would become overcharged before the lowest cells became fully charged. This would cause damage to the batteries and shorten their lifespan. The battery pack in the photo above cost $1000, but a battery pack big enough for an electric car can cost $10-15,000 or more. A BMS is essential to protect such expensive parts.

    Leave a comment:


  • starletkid
    replied
    yeah man,
    if ppl knew the song more it would have been perfect!
    good for those covert jobs.
    lol

    Leave a comment:


  • mauswerkz
    replied
    Originally posted by Crazy2287 View Post
    Blinkies! It's good to see these little squares working. Are you going to add temperature monitoring for the test pack before you use it?
    Nah, not going to bother monitoring temps on the test pack. It's not really that nessecary. I've only included it as a feature because that's what the competition has.

    Originally posted by starletkid View Post
    man when i seen this thread, it reminded me of this song..

    it made me laugh how much it reminded me of this....
    http://youtu.be/nMqxNPsfN50
    Finally, somebody got the reference!

    Leave a comment:

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