Power in Flux
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  1. #11
    Senior Member Podbuilder's Avatar
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    Excellent. I can just run the wires through the water pipe, represented in red on the CAD drawing.



    Brad.

  2. #12
    Ghost Rider Allen_okc's Avatar
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    i think this is another outside of the box build, i love it and would like to say anything artistic can be built now a days and be totally functional - so i applaud your build and would also like to say bring on plenty of pics...

    but when it comes to your drive train, these fellows here know their stuff and can help you build a successful EV... Welcome to Elmoto and congratulations on this awesome challenge...
    The Greatest thing about a EV, is the Song of the Terrain...

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  4. #13
    Empulse R #24 frodus's Avatar
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    Maybe consider using 24S, it makes finding a charger much easier IMHO. Most charger manufacturers can fine tune them for a price, but if you want off the shelf and cheaper, consider adding another 1s to that 23S. It might not fit like you want, but it makes finding a charger and DC-DC easier. I couldn't imagine 4 more cells would hurt ya much.
    Travis

  5. #14
    Senior Member Podbuilder's Avatar
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    Quote Originally Posted by frodus View Post
    Maybe consider using 24S, it makes finding a charger much easier IMHO. Most charger manufacturers can fine tune them for a price, but if you want off the shelf and cheaper, consider adding another 1s to that 23S. It might not fit like you want, but it makes finding a charger and DC-DC easier. I couldn't imagine 4 more cells would hurt ya much.
    Good advise... just the technical stuff I need to hear.

  6. #15
    Senior Member Podbuilder's Avatar
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    Using a Hub motor would free up more space at the core of the bike. By my estimations another 34 cells in the frame.



    I'd just need to make the frames a little wider. So I could in theory do 24s5p.

    Brad.

  7. #16
    Senior Member Podbuilder's Avatar
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    Another option.. If I go hub motor which looks like a better option I can fit 24 Winston LFP40AH cells in the frame.



    24 cells costing $1440 giving 72v 40Ah as opposed to headway cells 72v 40Ah 24s4p $ 1728 or possible Headway 24s5p even more costly... BUT the hub motor from Mark I'm sure will be more expensive.

    Given my lack of experience here, I'm looking for some feedback.

    Just doing some more reading... seems Marks prefers motors at 144v. Correct me if Im wrong but at the higher voltage they create less heat?? So if its a 144v motor it would need to be 96 headway cells.

    Brad.
    Last edited by Podbuilder; 11 September 2013 at 0607. Reason: Cause I like reading about this stuff!!

  8. #17
    Member PaulWay's Avatar
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    Here, have a play with this:

    72 volt pack, 50 kilos maximum, sorted in order of price, with only cells that someone's actually selling. You can change all those settings and more

    So in general voltage of the battery is proportional to top speed - for the Enertrac MHM-602, if you put in 96 volts, you go 100 km/hr. In order to go 50 km/hr, the controller supplies 48 volts to the motor. You can run that motor on a 72 volt pack, and all that you'll do is limit your top speed to around 75 km/hr. (It's that voltage that fights against the motor's own EMF, called back EMF).

    Now, controllers generally have a maximum voltage that they can cope with before things start to electrically fail inside - and a lower limit which the software detects and will refuse to run because that high voltage mark signals a problem. So if you're going to get a 144 volt battery, make sure to get at least 144 volt controller. OTOH, there's minimal extra penalty in getting a controller that has a higher maximumn voltage than you need - they just cost more (and weight a fraction more) is all

    The other factor is: current is proportional to torque. The more current your battery can produce, the more the controller can feed to the motor, and the faster you'll accelerate up to that voltage speed limit.

    Final bit of math: the amount of power the motor uses is proportional to the amount of heat it generates. Power is volts by amps, so if you're using 10KW of power you're producing a proportion of that as heat (e.g. 90% efficient motor? 1KW of heat). That's the same whether you're just cruising along at top speed, or accelerating hard and then braking hard. It's only ephemerally related to the voltage of your battery.

    The complication in the battery business here is that every cell has a measure (called the C rating) which defines how much current it can produce. The C rating is given as a proportion of the amp-hours of the cell - so a 40AH cell rated to 3 C can produce 40 * 3 = 120 amps. A 120AH cell rated to 1 C can also give 120 * 1 = 120 amps - but it will do so for considerably longer than the 40AH battery (more stored power, mainly).

    Which means that you can start with a 96V controller and a 24S 72V pack of 10AH Headways and you'll get a low top speed, slow acceleration and not much running time. Then you can add another eight Headways to make 96V and you'll go faster but still get the same acceleration and run time. Or you buy another 24 cells, hook them up in parallel and you have the same top speed, double the acceleration, and (to a reasonable approximation) double the run time.

    The 40AH Winston cells constrain you more, both in terms of how you hook them up initially and your upgrade options in the future. But they may be simpler to hook up, and simpler to manage, than that many watt-hours of Headway cells. It's all a trade off.

    BTW, in that picture you have them stacked on top of eachother and packed all over the place. I'd suggest getting a lot more organised about how they're stored and laid out. You'll have to connect wires between the terminals of each cell, and in general that's easier when the cells are in a nice line. They also prefer to be upright or with the thin edge up - don't put them flat side up or the internal plate can dry out and you lose capacity. You'll also want to think about how to get the battery power through a contactor (a big relay to turn the whole thing on), to the controller, and thence to the motor.

    Hope this helps,

    Paul

    P.S. Ted and Noah may be more knowledgeable than I am at this electrical engineering.
    Last edited by PaulWay; 11 September 2013 at 2155.

  9. #18
    Senior Member Podbuilder's Avatar
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    Excellent information PaulWay. I like the idea for growing the battery bank as required. This will help the budget and keep the wife happy!! I made contact with Enertrac, now just need to hear what he suggests. He mentioned a single motor system single sided mounting with a four or five bolt car wheel pattern. So hopefully I'll get more information on this shortly.

    Brad.

  10. #19
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    I'm going the hub wheel from Mark option. It's more expensive for the motor but as there is no axles, sprockets and chains required in the frame for this design ill save on some weight and $$ for these parts. Also, extra battery space will give me extra run time.

    I should be making a start on frame soon, now I've decided on the cells and motor.

    Brad.

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  12. #20
    Senior Member Podbuilder's Avatar
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    Ordered my motor from Mark.



    Controller from Kelly 24 - 96v 350 amp KBL96351E. Also contactor, fuse, fuse holder and throttle coming from Kelly. Mark suggested a 72v battery for my set-up usage. Can anyone suggest a place to purchase Headway cells with charging gear that you have used using Paypal? What else do I need?

    Brad.

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