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Thread: Step by Step Circuit Diagram Buildup

              
   
   
  1. #1
    Member bugeyebug's Avatar
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    Step by Step Circuit Diagram Buildup

    I'm starting to layout my overall wiring diagram/schematic. Being the paranoid individual I am, I'd like to do this in a step-by-step manner and catch any problems before they morph into something bigger. With that in mind, here's the first part of the circuit, which is the main controller/battery/motor drive circuit. There's obviously a lot still to come, but for now I'm looking for some basic feedback from the experts on the list:



    A couple of questions:

    1) Main Fuse Location. Can I place the main circuit fuse in the position shown? Or does it have to be on the "Plus" side of the battery bank? Most of the circuits I've seen shown it on the plus side, but it seems to me that either is OK.

    2) Emergency Disconnect Switch. I'm thinking of adding a large, manual-style high voltage emergency disconnect switch in line with the main contactor. Something like an Albright ED250 mushroom head switch that interrupts the circuit when it's hit by hand. Is this a good or bad idea? What do other people do in this regard?

    Thanks in advance,
    Mark

  2. #2
    Señor Member podolefsky's Avatar
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    Looks good so far. You need power to the contactor coil, and also pack voltage to pin 1 on the Alltrax.

    Fuse can go on either B+ or B-. Closer to the pack is better.

    Generally, your contactor *is* your emergency disconnect. Hook up a kill switch up so that you can kill power to the coils. I use the original kill switch on my handlebars, but my contactor coil is 24V so it's OK. If you're running pack voltage to the coil, you'll need a kill switch that can interrupt pack voltage.

    If you do go with the Albright, you want the ED250B (rated for 96V). The ED250 is only rated for 48V. But they only have a continuous current rating of 250A, and breaking current of 1000A. If you have a fault and need to break the circuit, you could be over 1000A. A contactor like the LEV200 can carry 500A continuous and break around 4000A at 80V. Much safer option, in my opinion.
    - Noah Podolefsky -
    The GSX-E

  3. #3
    Member bugeyebug's Avatar
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    Thanks for the input Noah. I really appreciate it. FWIW, I added the next layer of complexity to the circuit, and would love more feedback:



    To be more consistent with the Alltrax wiring diagram, I moved the big fuse to the plus side of the battery, and per Noah’s suggestion, I located it close to the pack.

    A few more questions come to mind:
    1. I wanted to used the stock Honda key switch and on/off switch, but I doubt if they’re 80-volt rated. How do I ensure they’re up to the task of 80V?
    2. What purpose does the diode across the contactor serve?
    3. What purpose does the “precharge” resistor serve?
    4. What purpose does the “reverse protection” diode serve?

    Thanks again...

  4. #4
    Señor Member podolefsky's Avatar
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    Nice looking diagram.

    You're key switch won't handle 80V. There are a bunch of workarounds for this - most involve using a relay (I prefer a solid state relay). Then the 12V system powers the relay to turn on the high voltage system. (There is a conundrum with how you turn on the 12V system so that you can use it to turn on the HV system...we can get into that later).

    The diode protects the coils from large voltage spikes when the coil is disconnected (it's property of coils that when the current changes quickly, the voltage shoots way up).

    The precharge resistor lets the capacitors in the controller charge up.

    I believe the reverse protection diode also protects the system from voltage spikes (I think from disconnecting the coil, but might be other sources as well).
    - Noah Podolefsky -
    The GSX-E

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  6. #5
    Member bugeyebug's Avatar
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    Looking at this circuit (which is obviously based on Alltrax's literature) it now does seem weird to me that I'm going to switch on the main high voltage circuit with a high voltage circuit. Yes, the current is certainly less, but if something goes wrong I've got the full pack voltage being used. I'd like to know more about how to use a lower 12V system to switch on the system. For instance, I've got a Sevcon 622/11202 DC-DC converter on order, and am wondering if there's a way to use its output to switch things on (but then of course I've got to switch *that* system on... sigh)

    Am I over thinking this?

  7. #6
    Señor Member podolefsky's Avatar
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    Not overthinking it at all - it's a pretty common issue. The Sevcon has a separate enable pin that takes pack voltage to turn it on. I'm not 100% sure, but it might be current limited, in which case you might be able to get away with using a 12V switch on the enable pin. The main problem with using high voltage on low voltage switches is arcing, but if the enable pin input has a pretty low current limit it might prevent arcing and you'd be OK.

    Again, I'm not sure, but this could be a way around the problem. Then you could use the 12V output from the Sevcon to activate relays that control all the high voltage stuff.
    - Noah Podolefsky -
    The GSX-E

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    Senior Member __Tango's Avatar
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    I don't know much about the alltrax controllers, but If i understand what you're doing, it's actually pretty simple. Basically, your DC/DC will take its input from the traction pack 76.8V, and output 12VDC. You can power your existing 12V subsystem (lights, ignition switch, etc) from that 12V output.

    You then can hook up the circuit that contains the key switch and run switch directly to the coils of the contactor (thus driving your contactor from the 12V circuit instead of your high power circuit).

    Good luck.
    EVs: 2007 Zapino Scooter, Honda VF500 Conversion (electriceptor.wordpress.com), Red Nissan LEAF SL (Arrived!)

  9. #8
    Señor Member podolefsky's Avatar
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    What Tango said is right. You just need to make sure you have a 12V coil contactor. Often the ones that come with the 7245 packages are 72V coils.

    It's also a good idea to have a way to turn off the DC-DC. Without any load, power drain is probably pretty small, but if you're storing your bike for more than a few hours or days it's a good idea to turn the DC-DC completely off.
    - Noah Podolefsky -
    The GSX-E

  10. #9
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    Well, I was going to say that the reverse protection diode is unneccesary because the solenoid is dc and so will work either polarity anyway. But, then it seemed like a good idea to leave it in but put it in the line to pin 1 of the contactor because that's its proper function, to protect the controller enable against reverse input. However, if you did that, the contactor would still operate with a reversed battery and the main B+ and B- controller inputs would be reversed which would completely sh*g it. So all in all, pretty good place to leave it where it is

  11. #10
    Member bugeyebug's Avatar
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    I've got a Sevcon 622/11202 DC-DC on order, and looking at an online wiring diagram, it appears there is an enable switch/circuit that turns the 12V output on and off. Here the schematic:
    Sevcon DC-DC Circuit.JPG

    Question: what do you think of using this as step 1 of turning on the overall system. I.e., I switch on the DC-DC converter, which creates a source of 12V power, which I can then use to turn on the main power circuit? Or am I not really solving anything by doing this; in other words, I'm still switching 76 Volts on/off in the enable circuit.

    Help! My head is starting to hurt. Am I worried about something that I shouldn't be worried about?

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