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bugeyebug
02 June 2012, 1552
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:

http://i527.photobucket.com/albums/cc355/bugeyebug/Electric%20Motorcycle/WiringDiagram01.jpg

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

podolefsky
02 June 2012, 2127
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.

bugeyebug
03 June 2012, 1150
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:

http://i527.photobucket.com/albums/cc355/bugeyebug/Electric%20Motorcycle/WiringDiagram02.jpg

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...

podolefsky
03 June 2012, 1224
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).

bugeyebug
03 June 2012, 1618
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?

podolefsky
03 June 2012, 1646
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.

__Tango
03 June 2012, 1651
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.

podolefsky
03 June 2012, 1820
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.

magicsmoke
03 June 2012, 1912
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 :)

bugeyebug
04 June 2012, 1728
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:
3249

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?

liveforphysics
04 June 2012, 1802
The enable line draws <0.1mA You can use any key switch you want directly from the enable.

Pack the connector to the DC/DC and your keyswitch with diaelectric grease or use a pull-up resistor, or a drip of water in the wrong spot can turn on the Sevcon DC/DC

bugeyebug
15 June 2012, 0646
My EE friend agrees that I *can* use the OEM key switch to handle full pack voltage, but he said he'd avoid it if possible. Here's his preferred method. The 12V battery is used to power the contactor that enables the DC-DC system. Then 12V is used to turn on the bigger contractor with the smaller one. It feels a bit like overkill to me, but I have to admit that it keeps the OEM switches operating at their rated voltages. As usual, comments and/or suggestions are greatly welcome.
http://i527.photobucket.com/albums/cc355/bugeyebug/Electric%20Motorcycle/WiringDiagram04.jpg

frodus
15 June 2012, 0659
do you have the SW200 yet? Is the coil pack voltage?

It's seems a bit overkill to run a contactor and relay, but if you have the contactor already, use it. If not, consider getting one with a 12V coil on it, and it'd eliminate the little relay.

bugeyebug
15 June 2012, 0828
Yes, I have the SW200 (it came with my controller and motor)... but I still have to buy the smaller contactor to operate it per my diagram. Therefore, maybe you're right; i.e., I should think about getting a contactor that has 12V operation, but can handle the big voltage on the other side. This would simplify things.

Does anyone have a preferred part number or model of contactor that takes 12V input, but can handle the big voltage on the controlled side? Where's a good place to shop for such animals?

thanks again. you guys rock.

podolefsky
15 June 2012, 0835
My EE friend agrees that I *can* use the OEM key switch to handle full pack voltage, but he said he'd avoid it if possible. Here's his preferred method. The 12V battery is used to power the contactor that enables the DC-DC system. Then 12V is used to turn on the bigger contractor with the smaller one. It feels a bit like overkill to me, but I have to admit that it keeps the OEM switches operating at their rated voltages. As usual, comments and/or suggestions are greatly welcome.

You can use the 12V keyswitch for the enable without a problem, because the enable input has such a low current limit. The place you run into trouble is when there isn't a current limit - the keyswitch *will* work, for a while. Eventually arcing will burn out the contacts. With the low current, you won't get any arcing and you'll be fine.

Keyswitch to DC-DC enable, then a 12V contactor coil run from the DC-DC would be simplest.

podolefsky
15 June 2012, 0838
Yes, I have the SW200 (it came with my controller and motor)... but I still have to buy the smaller contactor to operate it per my diagram. Therefore, maybe you're right; i.e., I should think about getting a contactor that has 12V operation, but can handle the big voltage on the other side. This would simplify things.

Does anyone have a preferred part number or model of contactor that takes 12V input, but can handle the big voltage on the controlled side? Where's a good place to shop for such animals?

thanks again. you guys rock.


LEV200 or EV200. Both are great, totally sealed, come in 12V versions. The EV200 has a coil "economizer" that uses less power, and it's nice and small. Either will work fine from your DC-DC.

frodus
15 June 2012, 0842
The smaller one is usually called a relay not contactor since it's low current. High current relays are called contactors.

What is the coil voltage of your sw200?

Lots of people use the ev200 and they're cheap on eBay and go up to 900vdc. And they're sealed.

bugeyebug
16 June 2012, 0814
Okay, how does this look?

http://i527.photobucket.com/albums/cc355/bugeyebug/Electric%20Motorcycle/WiringDiagram06.jpg
A few things to note:

I'm starting to get more comfortable with the idea of running high voltage/low current through the OEM key switch. I also like the idea of eliminating the relay to activate the main contactor. What this means, however, is I now have to buy a different main contactor than the one currently in my possession... ah, but so be it. I can sell the existing SW200 unit on eBay or the forums, and recoup some of my money. Said another way, I'm more interested in doing this all correctly (and simplify things) than skimping on a few bucks.
I also like the idea of not carrying around a heavy, bulky 12V aux battery. Space is limited on the bike as it is, and if I can do away with this unit, I'll be quite happy.
I think I need an on/off enable switch on the 12V side of the DC-DC converter to ensure the aux equipment can be turned off in the event the converter fails in the On configuration. This is unlikely to happen, but a switch seems cheap insurance to add.
I've included a master manually-operated disconnect switch on the negative side of the battery bank. This will be used primarily when I'm doing maintenance on the bike (i.e., to isolate the battery), but will also be located in a prominent front-and-center location where I can operate it in the event of an emergency. Is this reasonable?

Comments/Suggestions/Criticisms/Rotten-Tomatoes are welcome...

podolefsky
16 June 2012, 1003
Looks good. Very clean diagram. Nice job.

Move the main fuse to the other side of the charger connection, so that there is nothing between B+ and the fuse.

You can (probably should) use more like a 10A fuse on the HV side of the DC-DC. If it's 20A output at 12V, that's going to be about 3A at 76V input side.

Not sure you need a fuse just for the contactor coil. I guess it can't hurt, but seems unnecessary.

Having the disconnect switch is a good idea. Just know that it's only rated to break 800A. In most situations that should be fine, but if you have a controller fault that shorts the battery to motor, you could see well over 1000A. In that case, the LEV200 is going to be your only safety valve.

frodus
16 June 2012, 1012
The charger should have it's own fuse unless the manual specs otherwise.

In this situation, I'd 100% go with an EV200 (the one with economizer) as it uses less current to hold and it's a bit smaller.

The output of the DC-DC doesn't really need to be switched. An ON/OFF on the enable line to the DC-DC will turn it off completely. Turning off the output doesn't turn off the DC-DC, it'll still idle and use power.

+1 on the lower rating fuse on the input to the DC-DC, it's way too high and the "low current" fuse on the input is redundant (unless the DC-DC manual specs it).

Your fuse on the Contactor is fine, and you should really have a fuse for all loads (kind of like the fuse block on a motorcycle)... but since you fuse before it, you may be OK without it.

If you DO use that shutoff as emergency, don't expect it to work more than ONCE under load. It WILL be damaged.